U.S. patent application number 17/723656 was filed with the patent office on 2022-08-04 for curved element for a ventricular assist device.
The applicant listed for this patent is Magenta Medical Ltd.. Invention is credited to Yinnon Elisha, Hagit Zemer Harel, Gad Lubinsky, Shaul Jacob Leisner Mustacchi, Avi Rozenfeld, Ehud Schwammenthal, Zev Sohn, Yuri Sudin, Victor Troshin, Yosi Tuval.
Application Number | 20220241576 17/723656 |
Document ID | / |
Family ID | 1000006276619 |
Filed Date | 2022-08-04 |
United States Patent
Application |
20220241576 |
Kind Code |
A1 |
Tuval; Yosi ; et
al. |
August 4, 2022 |
CURVED ELEMENT FOR A VENTRICULAR ASSIST DEVICE
Abstract
Apparatus and methods are described including delivering a
left-ventricular assist device to a subject's left ventricle. A
tube is positioned such that a proximal portion of the tube
traverses an aortic valve of the subject, and a distal portion of
the tube is disposed within a left ventricle of the subject. A pump
pumps blood through the tube from the subject's left ventricle to
the subject's aorta. A curved element is disposed within the tube
and is configured to cause at least a portion of the tube to become
curved. Other applications are also described.
Inventors: |
Tuval; Yosi; (Even Yehuda,
IL) ; Sohn; Zev; (Karnei Shomron, IL) ;
Schwammenthal; Ehud; (Ra'anana, IL) ; Lubinsky;
Gad; (Ein Vered, IL) ; Troshin; Victor;
(Hod-Hasharon, IL) ; Mustacchi; Shaul Jacob Leisner;
(Ra'ananna, IL) ; Elisha; Yinnon; (Kffar Hess,
IL) ; Sudin; Yuri; (Modi'in-Makkabbim-Re'ut, IL)
; Harel; Hagit Zemer; (Kfar Saba, IL) ; Rozenfeld;
Avi; (Haifa, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Magenta Medical Ltd. |
Kadima |
|
IL |
|
|
Family ID: |
1000006276619 |
Appl. No.: |
17/723656 |
Filed: |
April 19, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16810121 |
Mar 5, 2020 |
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17723656 |
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16750354 |
Jan 23, 2020 |
11191944 |
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16810121 |
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62796138 |
Jan 24, 2019 |
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62851716 |
May 23, 2019 |
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62870821 |
Jul 5, 2019 |
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62896026 |
Sep 5, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 60/216 20210101;
A61M 60/422 20210101; A61M 60/857 20210101; A61M 2205/0216
20130101; A61M 60/135 20210101; B05D 1/02 20130101; A61M 60/205
20210101; F04D 29/526 20130101; A61M 60/818 20210101; A61M 60/808
20210101; A61M 60/148 20210101; A61M 2205/3344 20130101; A61M
60/126 20210101; A61M 2230/30 20130101; A61M 60/896 20210101; F04D
29/545 20130101; A61M 60/419 20210101; A61M 60/122 20210101; A61M
60/829 20210101; A61M 60/414 20210101; F04D 29/382 20130101 |
International
Class: |
A61M 60/148 20060101
A61M060/148; A61M 60/419 20060101 A61M060/419; A61M 60/422 20060101
A61M060/422; A61M 60/818 20060101 A61M060/818; A61M 60/829 20060101
A61M060/829; A61M 60/857 20060101 A61M060/857; A61M 60/896 20060101
A61M060/896; A61M 60/414 20060101 A61M060/414; A61M 60/135 20060101
A61M060/135; F04D 29/52 20060101 F04D029/52; F04D 29/54 20060101
F04D029/54; F04D 29/38 20060101 F04D029/38; B05D 1/02 20060101
B05D001/02; A61M 60/808 20060101 A61M060/808; A61M 60/126 20060101
A61M060/126; A61M 60/216 20060101 A61M060/216 |
Claims
1. An apparatus, comprising: a left-ventricular assist device
configured to assist left-ventricular functioning of a subject, the
left-ventricular assist device comprising: a tube configured such
that a proximal portion of the tube traverses an aortic valve of
the subject, and a distal portion of the tube is disposed within a
left ventricle of the subject, the tube defining a set of one or
more blood-inlet openings that are configured to be disposed within
the subject's left ventricle, and a set of one or more blood-outlet
openings that are configured to be disposed within the subject's
aorta; a frame disposed within the distal portion of the tube, the
frame being configured to hold the distal portion of the tube in an
open state; a pump disposed within the frame and configured to pump
blood through the tube from the subject's left ventricle to the
subject's aorta, by pumping the blood into the tube via the one or
more blood-inlet openings and by pumping blood out of the tube via
the one or more blood-outlet openings; and a curved element
disposed within the tube, the curved element being configured to
cause at least a portion of the tube to become curved.
2. The apparatus according to claim 1, wherein the curved element
is configured to cause at least the portion of the tube to become
curved, such that the tube curves away from a posterior wall of the
left ventricle.
3. The apparatus according to claim 1, wherein the curved element
is configured to cause at least the portion of the tube to become
curved, such that the tube curves away from a septal wall of the
left ventricle.
4. The apparatus according to claim 1, wherein the curved element
is configured to cause at least the portion of the tube to become
curved, such that the tube curves toward a free wall of the left
ventricle.
5. The apparatus according to claim 1, the curved element is
configured to cause at least the portion of the tube to become
curved, such that the tube curves toward an apex of the left
ventricle.
6. The apparatus according to claim 1, the curved element is
configured to cause at least the portion of the tube to become
curved, such that a separation is maintained between the one or
more blood-inlet openings and a posterior wall of the left
ventricle, mitral valve leaflets of the subject, chordae tendineae
of the subject, and papillary muscles of the subject.
7. The apparatus according to claim 1, wherein the left-ventricular
assist device further comprises a drive cable, wherein the curved
element comprises a hypotube disposed around a section of the drive
cable.
8. The apparatus according to claim 1, wherein the curved element
is configured to cause a portion of the tube which is proximal to
the frame and which is disposed within the left ventricle to become
curved.
9. The apparatus according to claim 1, wherein the left-ventricular
assist device further comprises a drive cable, and one or more
outer tubes disposed around the drive cable, wherein the curved
element comprises a portion of one or more of the outer tubes.
10. The apparatus according to claim 1, wherein the tube is
pre-shaped such that a portion of the tube is configured to become
curved during the pumping of blood through the tube.
11. The apparatus according to claim 10, wherein the tube is
pre-shaped such that, during the pumping of blood through the tube,
the tube curves away from a posterior wall of the left
ventricle.
12. The apparatus according to claim 10, wherein the tube is
pre-shaped such that, during the pumping of blood through the tube,
the tube curves away from a septal wall of the left ventricle.
13. The apparatus according to claim 10, wherein the tube is
pre-shaped such that, during the pumping of blood through the tube,
the portion of the tube becomes curved, such that a separation is
maintained between the one or more blood-inlet openings and the
posterior wall of the left ventricle, mitral valve leaflets of the
subject, chordae tendineae of the subject, and papillary muscles of
the subject.
14. The apparatus according to claim 1, wherein at least one of the
sets of blood-inlet openings and blood-outlet openings is disposed
in a non-axi-symmetric configuration with respect to the tube, such
that pumping of the blood through the at least one of the sets of
blood-inlet openings and blood-outlet openings causes at least a
portion of the tube to become curved, such that the curvature of
the tube is maintained.
15. The apparatus according to claim 14, wherein the one or more
blood-inlet openings are disposed on a side of the tube that is
inside of a curve defined by the tube such that as blood flows into
the blood-inlet openings, pressure in a region above the
blood-inlet openings is lowered, and the a distal end of the tube
is then pulled toward this region.
16. The apparatus according to claim 14, wherein the one or more
blood-outlet openings are disposed on a side of the tube that is
inside of a curve defined by the tube such that as blood exits the
blood-outlet openings the blood impacts a wall of the aorta,
causing a proximal end of the tube to be pushed in an opposite
direction from the flow of the blood exiting the blood-outlet
openings.
17. The apparatus according to claim 1, wherein blood pump
comprises an impeller disposed within the frame, and wherein the
curved element is disposed proximally with respect to the
impeller.
18. The apparatus according to claim 17, wherein the curved element
is disposed proximally with respect to the frame.
19. The apparatus according to claim 18, wherein the
left-ventricular assist device further comprises proximal and
distal bearings disposed respectively at proximal and distal ends
of the frame, wherein the curved element is disposed proximal to
the proximal bearing.
20. The apparatus according to claim 19, wherein the curved element
is disposed immediately proximal to the proximal bearing.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. Ser. No.
16/810,121 to Tuval, entitled "Frame for blood pump," filed Mar. 5,
2020 (published as US 2020/0237984), which is a continuation of
U.S. Ser. No. 16/750,354 to Tuval, entitled "Distal tip element for
a ventricular assist device," filed Jan. 23, 2020 (issued as U.S.
Pat. No. 11,191,944), which claims priority from:
[0002] U.S. Provisional Patent Application 62/796,138 to Tuval,
entitled "Ventricular assist device," filed Jan. 24, 2019;
[0003] U.S. Provisional Patent Application 62/851,716 to Tuval,
entitled "Ventricular assist device," filed May 23, 2019;
[0004] U.S. Provisional Patent Application 62/870,821 to Tuval,
entitled "Ventricular assist device," filed Jul. 5, 2019; and
[0005] U.S. Provisional Patent Application 62/896,026 to Tuval,
entitled "Ventricular assist device," filed Sep. 5, 2019.
FIELD OF EMBODIMENTS OF THE INVENTION
[0006] Some applications of the present invention generally relate
to medical apparatus. Specifically, some applications of the
present invention relate to a ventricular assist device and methods
of use thereof.
BACKGROUND
[0007] Ventricular assist devices are mechanical circulatory
support devices designed to assist and unload cardiac chambers in
order to maintain or augment cardiac output. They are used in
patients suffering from a failing heart and in patients at risk for
deterioration of cardiac function during percutaneous coronary
interventions. Most commonly, a left-ventricular assist device is
applied to a defective heart in order to assist left-ventricular
functioning. In some cases, a right-ventricular assist device is
used in order to assist right-ventricular functioning. Such assist
devices are either designed to be permanently implanted or mounted
on a catheter for temporary placement.
SUMMARY OF EMBODIMENTS
[0008] In accordance with some applications of the present
invention, a ventricular assist device includes an impeller
disposed upon an axial shaft, with a frame disposed around the
impeller. The ventricular assist device typically includes a tube,
which traverses the subject's aortic valve, such that a proximal
end of the tube is disposed in the subject's aorta and a distal end
of the tube is disposed within the subject's left ventricle. The
impeller, the axial shaft and the frame are disposed within a
distal portion of the tube inside the subject's left ventricle.
Typically, the impeller is configured to pump blood from the left
ventricle into the aorta by rotating. The tube typically defines
one or more blood inlet openings at the distal end of the tube, via
which blood flows into the tube from the left ventricle, during
operation of the impeller. For some applications, the proximal
portion of the tube defines one or more blood outlet openings, via
which blood flows from the tube into the ascending aorta, during
operation of the impeller.
[0009] For some applications, the ventricular assist device
includes a distal-tip element configured to define a straight
proximal portion that defines a longitudinal axis, and a curved
distal portion shaped such as to curve in a first direction with
respect to the longitudinal axis of the straight proximal portion
before passing through an inflection point and curving in a second
direction with respect to the longitudinal axis of the straight
proximal portion, such that the curved distal portion defines a
bulge on one side of the longitudinal axis of the straight proximal
portion. Typically, the distal-tip element has a question-mark
shape and/or a tennis-racket shape.
[0010] For some applications, the distal-tip element is configured
to separate the blood inlet opening from a posterior wall of the
subject's left ventricle when the distal-tip element is placed
against the apex of the subject's left ventricle. Typically, the
distal-tip element is configured to separate the blood inlet
opening from a septal wall of the subject's left ventricle as the
distal-tip element contacts the apex of the subject's left
ventricle. Further typically, the distal-tip element is configured
such that, when distal-tip element is inserted into the left
ventricle such that the bulge bulges toward the septal wall, in
response to the distal-tip element being pushed against the apex of
the subject's left ventricle, the blood inlet opening gets pushed
away from the septal wall and toward a free wall of the subject's
left ventricle. For some applications, the blood inlet opening gets
pushed away from the septal wall and toward the free wall of the
subject's left ventricle by the straight proximal portion of the
distal-tip element pivoting about the curved distal portion of the
distal-tip element.
[0011] For some applications, a duckbill valve is disposed within a
distal-most 10 mm of the distal-tip element. Typically, the
duckbill valve defines a wide inlet and a narrow tip that defines a
slit therethrough, the duckbill valve being proximally facing, such
that the wide inlet faces a distal end of the distal-tip element
and such that the narrow tip faces away from the distal end of the
distal-tip element. For some applications, the ventricular assist
device is configured for use with a guidewire, and the distal-tip
element defines a guidewire lumen. For some such applications, the
ventricular assist device further comprises a guidewire guide
disposed within the guidewire lumen at a location that is proximal
to the duckbill valve. The guidewire guide is typically shaped to
define a hole therethrough, which narrows in diameter from a
proximal end of the guidewire guide to a distal end of the
guidewire guide, the shape of the guidewire guide being configured
to guide a tip of the guidewire toward the slit at the narrow,
proximal end of the duckbill valve, when the guidewire is inserted
from a proximal end of the left-ventricular assist device. For some
applications, the duckbill valve is shaped to define a converging
guide portion at its proximal end, the converging guide portion
converging toward the slit, such that the guide portion is
configured to further guide the tip of the guidewire toward the
slit.
[0012] Typically, the frame that is disposed around the impeller
defines a plurality of cells, and the frame is configured such
that, in a non-radially-constrained configuration of the frame, the
frame comprises a generally cylindrical portion. Further typically,
a width of each of the cells within the cylindrical portion, as
measured around a circumference of the cylindrical portion, is less
than 2 mm (e.g., 1.4-1.6 mm, or 1.6-1.8 mm). For some applications,
an inner lining lines at least the cylindrical portion of the
frame, and the impeller is disposed inside the frame such that, in
a non-radially-constrained configuration of the impeller, at a
location at which a span of the impeller is at its maximum, the
impeller is disposed within the cylindrical portion of the frame,
such that a gap between an outer edge of the impeller and the inner
lining is less than 1 mm (e.g., less than 0.4 mm). Typically, the
impeller is configured to rotate such as to pump blood from the
left ventricle to the aorta, and to be stabilized with respect to
the frame, such that, during rotation of the impeller, the gap
between the outer edge of the impeller and the inner lining is
maintained and is substantially constant. For some applications,
the impeller is configured to reduce a risk of hemolysis, by being
stabilized with respect to the frame, relative to if the impeller
were not stabilized with respect to the frame.
[0013] For some applications, proximal and distal radial bearings
are disposed, respectively, at proximal and distal ends of the
frame, and an axial shaft passes through the proximal and distal
radial bearings. Typically, the impeller is stabilized with respect
to the frame by the impeller being held in a radially-fixed
position with respect to the axial shaft and the axial shaft being
rigid. For some applications, the impeller includes bushings that
are disposed around the axial shaft, and at least one of the
bushings is configured to be slidable with respect to the axial
shaft. For some applications, the impeller being stabilized with
respect to the frame by a region along the axial shaft over which
the at least one bushing is configured to be slidable with respect
to the axial shaft being coated, such as to substantially prevent
the impeller from vibrating, by reducing a gap between the at least
one bushing and the impeller. For example, the region may be coated
in a diamond-like-carbon coating, a polytetrafluoroethylene
coating, and/or a polymeric sleeve.
[0014] For some applications, the frame defines struts having a
structure that is such that, as the frame transitions from a
proximal end of the frame toward a center of the frame, the struts
pass through junctions, at which pairs of struts branch from a
single strut, in a Y-shape. The structure of the struts of the
frame is typically configured such that, in response to a distal
end of the delivery catheter and the frame being moved into
overlapping positions with respect to each other (e.g., by the
distal end of the delivery catheter being advanced over the frame,
or by the frame being retracted into the distal end of the delivery
catheter), the frame is configured to assume its
radially-constrained configuration by becoming axially elongated,
and is configured to cause the impeller to assume its
radially-constrained configuration by becoming axially elongated
(e.g., by the pairs of struts that branch from each of junctions
being configured to pivot about the junction and move closer to
each other such as to close in response to a distal end of the
delivery catheter and the frame being moved into overlapping
positions with respect to each other).
[0015] For some applications, a housing for an impeller of a blood
pump is manufactured by performing the following steps. An inner
lining is placed around a mandrel. A cylindrical portion of a frame
is placed around the inner lining, the cylindrical portion of the
frame including struts that define a generally cylindrical shape. A
distal portion of an elongate tube is placed around at least a
portion of the frame, the tube including a proximal portion that
defines at least one blood outlet opening. While the distal portion
is disposed around at least the portion of the frame, the inner
lining, the frame and the distal portion of the elongate tube are
heated, via the mandrel. While heating the inner lining, the frame
and the distal portion of the elongate tube, pressure is applied
from outside the distal portion of the elongate tube, such as to
cause the distal portion of the elongate tube to conform with a
structure of the struts of the frame, and such as to cause the
inner lining and the distal portion of the elongate tube to become
coupled to the frame. For example, the pressure may be applied by
means of a silicone tube that is placed outside the distal portion
of the elongate tube. For some applications, the inner lining and
the elongate tube include an inner lining and elongate tube that
are made from different materials from each other, and a
thermoforming temperature of a material from which the inner lining
is made is higher than a thermoforming temperature of a material
from which the elongate tube is made. For some such applications,
the inner lining, the frame and the distal portion of the elongate
tube are heated to a temperature that is above the thermoforming
temperature of the material from which the elongate tube is made
and below the thermoforming temperature of the material from which
the inner lining is made.
[0016] For some applications, the impeller is manufactured by
forming a structure having first and second bushings at proximal
and distal ends of the structure, the first and second bushings
being connected to one another by at least one elongate element.
The at least one elongate element is made to radially expand and
form at least one helical elongate element, at least partially by
axially compressing the structure. An elastomeric material is
coupled to the at least one helical elongate element, such that the
at least one helical elongate element with the elastomeric material
coupled thereto defines a blade of the impeller. Typically, the
coupling is performed such that a layer of the material is disposed
around a radially outer edge of the at least one helical elongate
element, the layer of material forming the effective edge of the
impeller blade (i.e., the edge at which the impeller's
blood-pumping functionality substantially ceases to be effective).
Further typically, the method includes performing a step to enhance
bonding of the elastomeric material to the at least one helical
elongate element in a manner that does not cause a protrusion from
the effective edge of the impeller blade. For example, sutures may
be placed within grooves defined by the at least one helical
elongate element, such that the sutures do not protrude from the
radially outer edge of the helical elongate element, the sutures
being configured to enhance bonding of the elastomeric material to
the at least one helical elongate element. Alternatively or
additionally, a tightly-wound coil is placed around the at least
one helical elongate element, such that the elastomeric material
forms a substantially smooth layer along a radially outer edge of
the coil, the coil being configured to enhance bonding of the
elastomeric material to the at least one helical elongate element.
Further alternatively or additionally, a sleeve is placed around
the at least one helical elongate element, such that the
elastomeric material forms a substantially smooth layer along a
radially outer edge of the sleeve, the sleeve being configured to
enhance bonding of the elastomeric material to the at least one
helical elongate element. For some applications, a rounded cross
section is provided to the at least one helical elongate element,
such that the elastomeric material forms a layer having a
substantially uniform thickness at an interface of the elastomeric
material with the helical elongate element.
[0017] In general, in the specification and in the claims of the
present application, the term "proximal" and related terms, when
used with reference to a device or a portion thereof, should be
interpreted to mean an end of the device or the portion thereof
that, when inserted into a subject's body, is typically closer to a
location through which the device is inserted into the subject's
body. The term "distal" and related terms, when used with reference
to a device or a portion thereof, should be interpreted to mean an
end of the device or the portion thereof that, when inserted into a
subject's body, is typically further from the location through
which the device is inserted into the subject's body.
[0018] The scope of the present invention includes using the
apparatus and methods described herein in anatomical locations
other than the left ventricle and the aorta. Therefore, the
ventricular assist device and/or portions thereof are sometimes
referred to herein (in the specification and the claims) as a blood
pump.
[0019] There is therefore provided, in accordance with some
applications of the present invention, apparatus including:
[0020] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including: [0021] a tube configured such that a
proximal portion of the tube traverses an aortic valve of the
subject, and a distal portion of the tube is disposed within a left
ventricle of the subject; [0022] a frame disposed within at least
the distal portion of the tube; [0023] a pump disposed within the
frame and configured to pump blood through the tube from the
subject's left ventricle to the subject's aorta, by pumping the
blood into the tube via at least one blood inlet opening that is
defined by the tube and that is configured to be disposed within
the subject's left ventricle, and by pumping blood out of the tube
via at least one blood outlet opening that is defined by the tube
and that is configured to be disposed within the subject's aorta;
and [0024] a distal-tip element configured to define a straight
proximal portion that defines a longitudinal axis, and a curved
distal portion that is shaped such as to curve in a first direction
with respect to the longitudinal axis of the straight proximal
portion before passing through an inflection point and curving in a
second direction with respect to the longitudinal axis of the
straight proximal portion, such that the curved distal portion
defines a bulge on one side of the longitudinal axis of the
straight proximal portion.
[0025] For some applications, the distal-tip element is configured
to separate the at least one blood inlet opening from a posterior
wall of the subject's left ventricle when the distal-tip element is
placed against an apex of the subject's left ventricle.
[0026] For some applications, the distal-tip element has a
question-mark shape. For some applications, the distal-tip element
has a tennis-racket shape.
[0027] For some applications, the curved distal portion of the
distal-tip element is shaped such that, after passing through the
inflection point, the curved distal portion continues to curve such
that the curved distal portion crosses back over the longitudinal
axis defined by the straight proximal portion. For some
applications, the curved distal portion of the distal-tip element
is shaped such that after passing through the inflection point the
curved distal portion does not cross back over the longitudinal
axis defined by the straight proximal portion.
[0028] For some applications, the blood pump includes an impeller
disposed on an axial shaft, and the distal-tip element includes an
axial-shaft-receiving tube configured to receive the axial shaft of
the blood pump, and a distal-tip portion configured to define the
curved distal portion of the distal-tip element.
[0029] For some applications, the distal-tip element is configured
to separate the at least one blood inlet opening from a septal wall
of the subject's left ventricle as the distal-tip element contacts
an apex of the subject's left ventricle. For some applications, the
distal-tip element is configured such that, when distal-tip element
is inserted into the left ventricle such that the bulge bulges
toward the septal wall, then in response to the distal-tip element
being pushed against the apex of the subject's left ventricle, the
blood inlet opening gets pushed away from the septal wall and
toward a free wall of the subject's left ventricle. For some
applications, the distal-tip element is configured such that, in
response to the distal-tip element being pushed against the apex of
the subject's left ventricle, the blood inlet opening gets pushed
away from the septal wall and toward the free wall of the subject's
left ventricle by the straight proximal portion of the distal-tip
element pivoting about the curved distal portion of the distal-tip
element.
[0030] For some applications, the distal-tip element is configured
such that, upon being deployed within a descending aorta of the
subject, the distal-tip element centers itself with respect to an
aortic valve of the subject. For some applications, the curved
distal portion is shaped that after curving in the first direction
the curved distal portion defines an elongated straight portion,
before curving the in the second direction, such that the elongated
straight portion protrudes at an angle with respect to the
longitudinal axis of the proximal straight portion of the
distal-tip element.
[0031] For some applications, a duckbill valve is disposed within a
distal-most 10 mm of the distal-tip element. For some applications,
the duckbill valve defines a wide inlet and a narrow tip that
defines a slit therethrough, the duckbill valve being proximally
facing, such that the wide inlet faces a distal end of the
distal-tip element and such that the narrow tip faces away from the
distal end of the distal-tip element.
[0032] For some applications:
[0033] the left-ventricular assist device is configured for use
with a guidewire;
[0034] the distal-tip element defines a guidewire lumen; and
[0035] the left-ventricular assist device further includes a
guidewire guide disposed within the guidewire lumen at a location
that is proximal to the duckbill valve, the guidewire guide shaped
to define a hole therethrough, which narrows in diameter from a
proximal end of the guidewire guide to a distal end of the
guidewire guide, the shape of the guidewire guide being configured
to guide a tip of the guidewire toward the slit at the narrow,
proximal end of the duckbill valve, when the guidewire is inserted
from a proximal end of the left-ventricular assist device.
[0036] For some applications, the duckbill valve is shaped to
define a converging guide portion at its proximal end, the
converging guide portion converging toward the slit, such that the
guide portion is configured to further guide the tip of the
guidewire toward the slit.
[0037] There is further provided, in accordance with some
applications of the present invention, apparatus including:
[0038] a blood pump configured to be placed inside a body of
subject, the blood pump including: [0039] an impeller; [0040] a
frame configured to be disposed around the impeller; [0041] a
distal-tip portion disposed distally with respect to the frame; and
[0042] a duckbill valve disposed entirely within a distal most 10
mm of the distal-tip portion, [0043] the duckbill valve defining a
wide inlet and a narrow tip that defines a slit therethrough,
[0044] the duckbill valve being proximally facing, such that the
wide inlet faces a distal end of the distal-tip portion and such
that the narrow tip faces away from the distal end of distal-tip
portion.
[0045] There is further provided, in accordance with some
applications of the present invention, apparatus for use with a
guidewire, including:
[0046] a percutaneous medical device defining a guidewire lumen
that extends from a proximal end of the device to a distal end of
the device;
[0047] a duckbill valve disposed within a distal portion of the
guidewire lumen, [0048] the duckbill valve defining a wide inlet
and a narrow tip that defines a slit therethrough, [0049] the
duckbill valve being proximally facing, such that the wide inlet
faces a distal end of guidewire lumen and such that the narrow tip
faces away from the distal end of guidewire lumen; and
[0050] a guidewire guide disposed within the guidewire lumen at a
location that is proximal to the duckbill valve, the guidewire
guide shaped to define a hole therethrough, which narrows in
diameter from a proximal end of the guidewire guide to a distal end
of the guidewire guide, the shape of the guidewire guide being
configured to guide a tip of the guidewire toward the slit at the
narrow, proximal end of the duckbill valve, when the guidewire is
inserted from the proximal end of the percutaneous medical
device.
[0051] For some applications, the duckbill valve is shaped to
define a converging guide portion at its proximal end, the
converging guide portion converging toward the slit, such that the
guide portion is configured to further guide the tip of the
guidewire toward the slit.
[0052] There is further provided, in accordance with some
applications of the present invention, apparatus including:
[0053] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including:
[0054] a tube configured to traverse an aortic valve of a subject,
such that a proximal end of the tube is disposed within an aorta of
the subject and a distal end of the tube is disposed within a left
ventricle of the subject;
[0055] a frame disposed within at least a portion of the tube, the
frame defining a plurality of cells, the frame being configured
such that, in a non-radially-constrained configuration of the
frame, the frame includes a generally cylindrical portion, a width
of each of the cells within the cylindrical portion as measured
around a circumference of the cylindrical portion being less than 2
mm;
[0056] an inner lining that lines at least some of the cylindrical
portion of the frame; and
[0057] an impeller disposed inside the frame such that, in a
non-radially-constrained configuration of the impeller, at a
location at which a span of the impeller is at its maximum, the
impeller is disposed within the cylindrical portion of the frame,
such that a gap between an outer edge of the impeller and the inner
lining is less than 1 mm,
[0058] the impeller being configured: [0059] to rotate such as to
pump blood from the left ventricle to the aorta, and [0060] to be
stabilized with respect to the frame, such that, during rotation of
the impeller, the gap between the outer edge of the impeller and
the inner lining is maintained and is substantially constant.
[0061] For some applications, the impeller is configured to reduce
a risk of hemolysis by being stabilized with respect to the frame,
relative to if the impeller were not stabilized with respect to the
frame.
[0062] For some applications, the width of each of the cells within
the cylindrical portion as measured around the circumference of the
cylindrical portion is between 1.4 mm and 1.6 mm.
[0063] For some applications, the width of each of the cells within
the cylindrical portion as measured around the circumference of the
cylindrical portion is between 1.6 mm and 1.8 mm.
[0064] For some applications, the impeller is configured such that
the gap between the outer edge of the impeller and the inner lining
is less than 0.4 mm.
[0065] For some applications:
[0066] the left-ventricular assist device further includes an axial
shaft and proximal and distal radial bearings disposed,
respectively, at proximal and distal ends of the frame, the axial
shaft passing through the proximal and distal radial bearings;
[0067] the impeller is coupled to the axial shaft; and
[0068] the impeller is stabilized with respect to the frame by the
impeller being held in a radially-fixed position with respect to
the axial shaft and the axial shaft being rigid.
[0069] For some applications, the impeller includes bushings that
are disposed around the axial shaft, at least one of the bushings
is configured to be slidable with respect to the axial shaft, and
the impeller is stabilized with respect to the frame by a region
along the axial shaft over which the at least one bushing is
configured to be slidable with respect to the axial shaft being
coated such as to substantially prevent the impeller from
vibrating, by reducing a gap between the at least one bushing and
the axial shaft.
[0070] For some applications, the impeller is stabilized with
respect to the frame by substantially preventing vibration of the
frame with respect to the axial shaft by a ratio of a length of the
cylindrical portion of the frame to a total length of the frame
being more than 1:2.
[0071] For some applications, the ratio of the length of the
cylindrical portion of the frame to the total length of the frame
is more than 2:3.
[0072] There is further provided, in accordance with some
applications of the present invention, apparatus including:
[0073] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including: [0074] a tube configured to traverse an
aortic valve of a subject, such that a proximal end of the tube is
disposed within an aorta of the subject and a distal end of the
tube is disposed within a left ventricle of the subject; [0075] a
frame disposed within at least a portion of the tube the frame
defining a plurality of cells, the frame being configured such that
in a non-radially-constrained configuration of the frame, the frame
includes a generally cylindrical portion; [0076] proximal and
distal radial bearings disposed, respectively, at proximal and
distal ends of the frame; [0077] an axial shaft that passes through
the proximal and distal radial bearings; [0078] an inner lining
that lines at least some of the cylindrical portion of the frame;
and [0079] an impeller coupled to the axial shaft inside the frame
such that, in a non-radially-constrained configuration of the
impeller, at a location at which a span of the impeller is at its
maximum, the impeller is disposed within the cylindrical portion of
the frame, such that a gap between an outer edge of the impeller
and the inner lining is less than 1 mm, [0080] the impeller
including bushings that are disposed around the axial shaft, at
least one of the bushings being configured to be slidable with
respect to the axial shaft, and [0081] the impeller being
stabilized with respect to the frame by a region along the axial
shaft over which the at least one bushing is configured to be
slidable with respect to the axial shaft being coated such as to
substantially prevent the impeller from vibrating, by reducing a
gap between the at least one bushing and the impeller.
[0082] For some applications, the region along the axial shaft over
which the at least one bushing is configured to be slidable with
respect to the axial shaft is coated with a diamond-like-carbon
coating. For some applications, the region along the axial shaft
over which the at least one bushing is configured to be slidable
with respect to the axial shaft is coated with a
polytetrafluoroethylene coating. For some applications, the region
along the axial shaft over which the at least one bushing is
configured to be slidable with respect to the axial shaft is coated
with a polymeric sleeve. For some applications, the impeller is
configured to reduce a risk of hemolysis by being stabilized with
respect to the frame, relative to if the impeller were not
stabilized with respect to the frame.
[0083] There is further provided, in accordance with some
applications of the present invention, apparatus including:
[0084] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including: [0085] a tube configured to traverse an
aortic valve of a subject, such that a proximal end of the tube is
disposed within an aorta of the subject and a distal end of the
tube is disposed within a left ventricle of the subject; [0086] a
frame disposed within at least a portion of the tube the frame
defining a plurality of cells, the frame being configured such that
in a non-radially-constrained configuration of the frame, the frame
includes a generally cylindrical portion; [0087] proximal and
distal radial bearings disposed, respectively, at proximal and
distal ends of the frame; [0088] an axial shaft that passes through
the proximal and distal radial bearings; [0089] an inner lining
that lines at least some of the cylindrical portion of the frame;
and [0090] an impeller coupled to the axial shaft inside the frame
such that, in a non-radially-constrained configuration of the
impeller, at a location at which a span of the impeller is at its
maximum, the impeller is disposed within the cylindrical portion of
the frame such that a gap between an outer edge of the impeller and
the inner lining is less than 1 mm, [0091] the impeller being
stabilized with respect to the frame by substantially preventing
vibration of the frame with respect to the axial shaft, by a ratio
of a length of the cylindrical portion of the frame to a total
length of the frame being more than 1:2.
[0092] For some applications, the ratio of the length of the
cylindrical portion of the frame to the total length of the frame
is more than 2:3.
[0093] For some applications, the impeller is configured to reduce
a risk of hemolysis by being stabilized with respect to the frame,
relative to if the impeller were not stabilized with respect to the
frame.
[0094] There is further provided, in accordance with some
applications of the present invention, a method, including:
[0095] manufacturing an impeller by: [0096] forming a structure
having first and second bushings at proximal and distal ends of the
structure, the first and second bushings being connected to one
another by at least one elongate element; [0097] causing the at
least one elongate element to radially expand and form at least one
helical elongate element, at least partially by axially compressing
the structure; and [0098] coupling an elastomeric material to the
at least one helical elongate element, such that the at least one
helical elongate element with the elastomeric material coupled
thereto defines a blade of the impeller, the coupling being
performed such that a layer of the material is disposed around a
radially outer edge of the at least one helical elongate element,
the layer of material forming the effective edge of the impeller
blade; [0099] the method including performing a step to enhance
bonding of the elastomeric material to the at least one helical
elongate element in a manner that does not cause a protrusion from
the effective edge of the impeller blade.
[0100] For some applications, manufacturing the impeller further
includes placing a spring within the structure such that the spring
extends from the first bushing to the second bushing, and coupling
the elastomeric material to the at least one helical elongate
element includes forming a film of the elastomeric material that
extends from the at least one helical elongate element to the
spring.
[0101] For some applications:
[0102] forming the structure includes forming a structure having
first and second bushings at proximal and distal ends of the
structure, the end portions being connected to one another by two
elongate elements;
[0103] causing the at least one elongate element to radially expand
and form at least one helical elongate element includes causing the
two elongate elements to radially expand and form two helical
elongate elements; and coupling the elastomeric material to the at
least one helical elongate element includes coupling the
elastomeric material to the two helical elongate elements, such
that the two helical elongate elements with the elastomeric
material coupled thereto define a blade of the impeller.
[0104] For some applications:
[0105] forming the structure includes forming a structure having
first and second bushings at proximal and distal ends of the
structure, the end portions being connected to one another by three
or more elongate elements;
[0106] causing the at least one elongate element to radially expand
and form at least one helical elongate element includes causing the
three elongate elements to radially expand and form three or more
helical elongate elements; and coupling the elastomeric material to
the at least one helical elongate element includes coupling the
elastomeric material to the three or more helical elongate
elements, such that each of the three or more helical elongate
elements with the elastomeric material coupled thereto defines a
respective blade of the impeller.
[0107] For some applications, causing the at least one elongate
element to radially expand and form at least one helical elongate
element further includes twisting the structure.
[0108] For some applications, performing the step to enhance
bonding of the elastomeric material to the at least one helical
elongate element includes placing sutures within grooves defined by
the at least one helical elongate element, such that the sutures do
not protrude from the radially outer edge of the helical elongate
element, the sutures being configured to enhance bonding of the
elastomeric material to the at least one helical elongate
element.
[0109] For some applications, performing the step to enhance
bonding of the elastomeric material to the at least one helical
elongate element includes placing a tightly-wound coil around the
at least one helical elongate element, such that the elastomeric
material forms a substantially smooth layer along a radially outer
edge of the coil, the coil being configured to enhance bonding of
the elastomeric material to the at least one helical elongate
element.
[0110] For some applications, performing the step to enhance
bonding of the elastomeric material to the at least one helical
elongate element includes placing a sleeve around the at least one
helical elongate element, such that the elastomeric material forms
a substantially smooth layer along a radially outer edge of the
sleeve, the sleeve being configured to enhance bonding of the
elastomeric material to the at least one helical elongate
element.
[0111] For some applications, performing the step to enhance
bonding of the elastomeric material to the at least one helical
elongate element includes providing a rounded cross section to the
at least one helical elongate element, such that the elastomeric
material forms a layer having a substantially uniform thickness at
an interface between the elastomeric material and the helical
elongate element.
[0112] There is further provided, in accordance with some
applications of the present invention, apparatus for use with a
delivery catheter including:
[0113] a blood pump including: [0114] an impeller configured to
pump blood through a subject's body; [0115] a frame disposed around
the impeller, [0116] the impeller and frame defining
non-radially-constrained configurations in which the impeller is
configured to pump blood within the subject's body, and defining
radially-constrained configurations in which the impeller and frame
are inserted and removed from the subject's body using a delivery
catheter, [0117] the frame defining struts having a structure that
is such that, as the frame transitions from a proximal end of the
frame toward a center of the frame, the struts pass through
junctions, at which the two struts branch from a single strut, in a
Y-shape; [0118] the structure of the struts of the frame being
configured such that, in response to a distal end of the delivery
catheter and the frame being moved into overlapping positions with
respect to each other, the frame is configured to assume its
radially-constrained configuration by becoming axially elongated,
and is configured to cause the impeller to assume its
radially-constrained configuration by becoming axially
elongated.
[0119] For some applications, the structure of the struts of the
frame is configured such that, in response to a distal end of the
delivery catheter and the frame being moved into overlapping
positions with respect to each other, the frame is configured to
assume its radially-constrained configuration by becoming axially
elongated, and is configured to cause the impeller to assume its
radially-constrained configuration by becoming axially elongated,
by the pairs of struts that branch from the junctions being
configured to pivot about the junction and move closer to each
other such as to close.
For some applications, in its radially-non-constrained
configuration, the frame defines a proximal conical portion, a
distal conical portion, and a cylindrical portion between the
proximal conical portion and the distal conical portion.
[0120] For some applications, within the cylindrical portion of the
frame, a strut density of the frame is constant.
[0121] For some applications, a density of the struts increases
from the proximal conical portion to the cylindrical portion, and
from the distal conical portion to the cylindrical portion.
[0122] For some applications, during operation of the blood pump,
the impeller is configured to move with respect to the frame, and a
range of movement of the impeller is such that at least a portion
of the impeller is disposed within the proximal conical portion of
the frame during at least some of the operation of the blood pump,
and at least a portion of the impeller is disposed within the
cylindrical portion of the frame during at least some of the
operation of the blood pump.
[0123] For some applications, throughout the operation of the blood
pump, at a location at which a span of the impeller is at its
maximum, the impeller is configured to be disposed within the
cylindrical portion of the frame.
[0124] For some applications, a width of each of the cells within
the cylindrical portion as measured around a circumference of the
cylindrical portion is less than 2 mm.
[0125] For some applications, the width of each of the cells within
the cylindrical portion as measured around the circumference of the
cylindrical portion is between 1.4 mm and 1.6 mm.
[0126] For some applications, the width of each of the cells within
the cylindrical portion as measured around the circumference of the
cylindrical portion is between 1.6 mm and 1.8 mm.
[0127] There is further provided, in accordance with some
applications of the present invention, a method, including:
[0128] manufacturing a housing for an impeller of a blood pump by:
[0129] placing an inner lining around a mandrel; [0130] placing,
around the inner lining, a cylindrical portion of a frame, the
cylindrical portion of the frame including struts that define a
generally cylindrical shape; [0131] placing a distal portion of an
elongate tube around at least a portion of the frame, the tube
including a proximal portion that defines at least one blood outlet
opening; [0132] while the distal portion is disposed around at
least the portion of the frame, heating the inner lining, the frame
and the distal portion of the elongate tube via the mandrel; and
[0133] while heating the inner lining, the frame and the distal
portion of the elongate tube, applying pressure from outside the
distal portion of the elongate tube, such as to cause the distal
portion of the elongate tube to conform with a structure of the
struts of the frame, and such as to cause the inner lining and the
distal portion of the elongate tube to become coupled to the
frame.
[0134] For some applications, the method further includes,
subsequent to causing the inner lining and the distal portion of
the elongate tube to become coupled to the frame, shaping a distal
end of the frame to define a widened inlet.
[0135] For some applications, the method further includes,
subsequent to causing the inner lining and the distal portion of
the elongate tube to become coupled to the frame, shaping a portion
of the frame to form a converging region, such that the frame
defines a narrowing in a vicinity of a location within the frame
that is configured to house the impeller.
[0136] For some applications, placing the distal portion of the
elongate tube around at least a portion of the frame includes
placing the distal portion of the elongate tube around the entire
cylindrical portion of the frame, such the distal portion of the
elongate tube overlaps with the entire inner lining.
[0137] For some applications:
[0138] the inner lining and the elongate tube include an inner
lining and elongate tube that are made from different materials
from each other, and a thermoforming temperature of a material from
which the inner lining is made is higher than a thermoforming
temperature of a material from which the elongate tube is made,
and
[0139] heating the inner lining, the frame and the distal portion
of the elongate tube includes heating the inner lining, the frame
and the distal portion of the elongate tube to a temperature that
is above the thermoforming temperature of the material from which
the elongate tube is made and below the thermoforming temperature
of the material from which the inner lining is made.
[0140] For some applications, applying pressure from outside the
distal portion of the elongate tube includes applying pressure from
outside the distal portion of the elongate tube using an outer tube
that is made of silicone.
[0141] For some applications, applying pressure from outside the
distal portion of the elongate tube, such as to cause the inner
lining and the distal portion of the elongate tube to become
coupled to the frame, includes coupling the inner lining to an
inner surface of the cylindrical portion of the frame, such that
the inner lining forms a substantially cylindrical tube.
[0142] For some applications, the struts within the cylindrical
portion of the frame are shaped to define cells, and a width of
each of the cells as measured around a circumference of the
cylindrical portion is less than 2 mm.
[0143] For some applications, placing the distal portion of the
elongate tube around at least a portion of the frame includes
placing the distal portion of the elongate tube around only a
portion of the cylindrical portion of the frame, such the distal
portion of the elongate tube does not overlap with the entire inner
lining.
[0144] For some applications, placing the distal portion of the
elongate tube around only a portion of the cylindrical portion of
the frame includes preventing radial expansion of the portion of
the cylindrical portion of the frame around which the distal
portion of the elongate tube is placed, thereby causing the portion
of the cylindrical portion of the frame around which the distal
portion of the elongate tube is placed to be narrower than a
portion of the cylindrical portion of the frame around which the
elongate tube is not placed.
[0145] There is further provided, in accordance with some
applications of the present invention, apparatus including:
[0146] a blood pump configured to be placed inside a body of
subject, the blood pump including: [0147] an impeller; [0148] a
frame configured to be disposed around the impeller, the frame
including struts; [0149] an inner lining disposed inside the frame;
[0150] an outer covering material coupled to the inner coupling
material from outside the frame at discrete coupling regions along
a length of the frame, [0151] a density of the struts of the frame
at the coupling regions being less than a density of the struts of
the frame at other regions along the length of the frame.
[0152] There is further provided, in accordance with some
applications of the present invention, apparatus including:
[0153] a blood pump configured to be placed inside a body of
subject, the blood pump including: [0154] an impeller; [0155] a
frame configured to be disposed around the impeller, the frame
including struts, and a cylindrical portion of the frame being
shaped to define a cylindrical cross-section; [0156] an inner
lining disposed inside the frame; [0157] an outer covering material
coupled to the inner coupling material from outside the frame, the
outer covering material being disposed around only a portion of the
cylindrical portion of the frame and the outer covering material
being configured to restrict radial expansion of the portion of the
cylindrical portion of the frame around which the outer covering
material is placed, such that the portion of the cylindrical region
of the frame around which the distal portion of the outer covering
material is placed is narrower than a portion of the cylindrical
region of the frame around which the outer covering material is not
placed.
[0158] There is further provided, in accordance with some
applications of the present invention, apparatus including:
[0159] a blood pump configured to be placed inside a body of
subject, the blood pump including: [0160] an impeller; [0161] a
frame configured to be disposed around the impeller, the frame
being configured to define a cylindrical portion that has a
substantially cylindrical cross-section; [0162] a covering material
that is coupled to the cylindrical portion of the frame, such that
a distal end of the cylindrical portion of the frame defines a
blood inlet opening, the impeller being configured to be disposed
within 15 mm of the blood inlet opening throughout operation of the
impeller, [0163] a portion of the frame being shaped such as to
reduce turbulence that is generated as blood flows from the blood
inlet opening toward the impeller.
[0164] For some applications, the portion of the frame includes a
widened portion of the frame.
[0165] For some applications, the portion of the frame includes a
portion of the frame that is shaped to converge toward the
impeller.
[0166] The present invention will be more fully understood from the
following detailed description of embodiments thereof, taken
together with the drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0167] FIGS. 1A, 1B, and 1C are schematic illustrations of a
ventricular assist device, a distal end of which is configured to
be placed in a subject's left ventricle, in accordance with some
applications of the present invention;
[0168] FIGS. 2A, 2B, 2C, 2D, 2E, and 2F are schematic illustrations
of a frame that houses an impeller of a ventricular assist device,
in accordance with some applications of the present invention;
[0169] FIGS. 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, 3I, 3J, and 3K are
schematic illustrations of an impeller of a ventricular assist
device or a portion thereof, in accordance with some applications
of the present invention;
[0170] FIG. 4 is a schematic illustration of an impeller disposed
inside a frame of a ventricular assist device, in accordance with
some applications of the present invention;
[0171] FIGS. 5A and 5B are schematic illustrations of the impeller
and the frame of the ventricular assist device, respectively in
non-radially-constrained and radially-constrained states thereof,
in accordance with some applications of the present invention;
[0172] FIG. 5C is a schematic illustration of a typical bearing
assembly that is used in prior art axial impeller-based blood
pumps;
[0173] FIGS. 6A and 6B are schematic illustrations of a ventricular
assist device at respective stages of a motion cycle of the
impeller of the ventricular assist device with respect to the frame
of the ventricular assist device, in accordance with some
applications of the present invention;
[0174] FIG. 6C is a schematic illustration of a distal-tip element
that includes an axial-shaft-receiving tube and a distal-tip
portion of a ventricular assist device, in accordance with some
applications of the present invention;
[0175] FIG. 6D is a schematic illustration of an axial shaft of a
ventricular assist device that is at least partially covered or
coated, such as to reduce a gap between the axial shaft and a
bushing of an impeller that slides over the axial shaft, in
accordance with some applications of the present invention;
[0176] FIG. 6E is a schematic illustration of an axial shaft of a
ventricular assist device and a bushing of an impeller that slides
over the axial shaft, the axial shaft and the impeller bushing
being configured to prevent rotational motion of the impeller
bushing with respect to the axial shaft, in accordance with some
applications of the present invention;
[0177] FIGS. 6F and 6G are schematic illustrations of an impeller
housing configured to provide a gap between the impeller and the
housing that varies over the course of a subject's cardiac cycle,
in accordance with some applications of the present invention;
[0178] FIG. 7 is a schematic illustration of a motor unit of a
ventricular assist device, in accordance with some applications of
the present invention;
[0179] FIGS. 8A and 8B are schematic illustrations of a motor unit
of a ventricular assist device, in accordance with some
applications of the present invention;
[0180] FIG. 9 is a graph indicating variations in the length of a
drive cable of a ventricular assist device as a pressure gradient
against which the impeller of the blood pump varies, as measured in
experiments performed by the inventors of the present
application;
[0181] FIGS. 10A, 10B, and 10C are schematic illustrations of a
drive cable of a ventricular assist device, in accordance with some
applications of the present invention;
[0182] FIGS. 10D, 10E, and 10F are schematic illustrations of the
drive cable and an axial shaft of the ventricular assist device, in
accordance with some applications of the present invention;
[0183] FIGS. 11A and 11B are schematic illustrations of an impeller
that is coupled to an axial shaft at the distal end of the impeller
and that is not coupled to the axial shaft at the proximal end of
the impeller, in accordance with some applications of the present
invention;
[0184] FIG. 11C is a schematic illustration of coupling portions
for facilitating the crimping of the impeller of FIGS. 11A and
11B;
[0185] FIG. 12A is a graph showing the relationship between the
pressure gradient against which the impeller is pumping and the
pitch of the impeller when the impeller is configured as shown in
FIG. 11A;
[0186] FIG. 12B is a graph showing pressure-flow curves for
impellers having respective pitches, in accordance with some
applications of the present invention;
[0187] FIGS. 13A, 13B, and 13C are schematic illustrations of a
procedure for purging a drive cable and/or radial bearings of a
ventricular assist device, in accordance with some applications of
the present invention;
[0188] FIG. 13D is a schematic illustration of a ventricular assist
device that includes an inflatable portion (e.g., a balloon)
disposed around its distal-tip portion, the inflatable portion
being configured to be inflated by a fluid that is used for purging
the drive cable of the device, in accordance with some applications
of the present invention;
[0189] FIG. 13E is a schematic illustration of a technique for
reducing frictional forces between a drive cable and an outer tube
in which the drive cable rotates and/or for reducing frictional
forces at radial bearings of a ventricular assist device, in
accordance with some applications of the present invention;
[0190] FIGS. 14A, 14B, and 14C are schematic illustrations of a
stator configured to be disposed inside a tube of a ventricular
assist device, proximal to a frame in which the impeller of the
ventricular assist device is disposed, in accordance with some
applications of the present invention;
[0191] FIGS. 15A, 15B, 15C, 15D, and 15E are schematic illustration
of a stator that is built into a tube of a ventricular assist
device, in accordance with some applications of the present
invention;
[0192] FIGS. 16A and 16B are schematic illustrations of a
ventricular assist device that includes one or more ventricular
blood-pressure-measurement tubes, in accordance with some
applications of the present invention;
[0193] FIGS. 16C and 16D are schematic illustrations of a
ventricular assist device having an aortic blood pressure
measurement channel within a delivery catheter, in accordance with
some applications of the present invention;
[0194] FIG. 16E is a schematic illustration of a ventricular assist
device that includes one or more sensors that are disposed on an
outer surface of a tube of the device, in accordance with some
applications of the present invention;
[0195] FIGS. 17A, 17B, 17C, and 17D are schematic illustrations of
a ventricular assist device that includes a pitot tube that is
configured to measure blood flow through a tube of the device, in
accordance with some applications of the present invention;
[0196] FIG. 18 is a schematic illustration of a ventricular assist
device that includes coronary artery tubes and/or wires, in
accordance with some applications of the present invention;
[0197] FIGS. 19A, 19B, 19C, 19D, 19E, 19F, 19G, and 19H are
schematic illustrations of a ventricular assist device that
includes an inner lining on the inside of the frame that houses the
impeller, in accordance with some applications of the present
invention;
[0198] FIGS. 20A, 20B, and 20C are schematic illustrations of a
ventricular assist device that includes an inflatable portion
(e.g., a balloon) disposed around its distal-tip portion, in
accordance with some applications of the present invention;
[0199] FIG. 21 is a schematic illustration of a ventricular assist
device being placed inside a subject's left ventricle, with a
transverse cross-sectional view of the left ventricle being
illustrated, in accordance with some applications of the present
invention;
[0200] FIGS. 22A, 22B, 22C, and 22D are schematic illustrations of
a distal-tip element of a ventricular assist device that is at
least partially curved such as to define a question-mark shape or a
tennis-racket shape, in accordance with some applications of the
present invention;
[0201] FIGS. 23A and 23B are schematic illustrations of the
ventricular assist device of FIG. 22D disposed inside a subject's
left ventricle, in accordance with some applications of the present
invention;
[0202] FIGS. 24A, 24B, and 24C are schematic illustrations of a
distal-tip element that is configured to center itself with respect
to a subject's aortic valve, in accordance with some applications
of the present invention;
[0203] FIGS. 25A, 25B, 25C, 25D, and 25E are schematic
illustrations of a ventricular assist device that includes a tube
that is configured to become curved when blood is pumped through
the tube, in accordance with some applications of the present
invention;
[0204] FIG. 25F is a schematic illustration of a ventricular assist
device that includes a curved element that is made of a
shape-memory material and that is configured to provide a portion
of the ventricular assist device with a predefined curvature, in
accordance with some applications of the present invention;
[0205] FIGS. 26A, 26B, 26C, 26D, 26E, and 26F are schematic
illustrations of a distal-tip element of a ventricular assist
device that is at least partially curved, in accordance with some
applications of the present invention;
[0206] FIGS. 27A, 27B, and 27C are schematic illustrations of an
atraumatic projection that includes a closed ellipse or a closed
circle and that is configured to extend distally from a distal-tip
element of a ventricular assist device, in accordance with some
applications of the present invention;
[0207] FIG. 28A is a schematic illustration of a duckbill valve and
guidewire guide disposed at the distal end of an atraumatic tip, in
accordance with some applications of the present invention;
[0208] FIGS. 28B and 28C are schematic illustration of respective
views of the duckbill valve of FIG. 28A, in accordance with some
applications of the present invention;
[0209] FIGS. 28D and 28E are schematic illustration of respective
views of the guidewire guide of FIG. 28A, in accordance with some
applications of the present invention;
[0210] FIG. 29 is a schematic illustration of a delivery catheter
that includes a sheath configured to facilitate reinsertion of a
guidewire through a percutaneous puncture, in accordance with some
applications of the present invention;
[0211] FIG. 30 is a schematic illustration of a ventricular assist
device that includes two impellers, in accordance with some
applications of the present invention;
[0212] FIG. 31 is a schematic illustration of a ventricular assist
device that includes two impellers, in accordance with some
applications of the present invention;
[0213] FIGS. 32A, 32B, 32C, 32D, and 32E are schematic illustration
of a ventricular assist device that is configured to assist the
functioning of the right heart of a subject, in accordance with
some applications of the present invention; and
[0214] FIG. 33 is a schematic illustration of a venous assist
device, in accordance with some applications of the present
invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0215] Reference is now made to FIGS. 1A, 1B, and 1C, which are
schematic illustrations of a ventricular assist device 20, a distal
end of which is configured to be disposed in a subject's left
ventricle 22, in accordance with some applications of the present
invention. FIG. 1A shows an overview of the ventricular assist
device system including a control console 21, and a motor unit 23,
FIG. 1B shows the ventricular assist device being inserted into the
subject's left ventricle, and FIG. 1C shows a pump portion 27 of
the ventricular assist device in greater detail. The ventricular
assist device includes a tube 24, which traverses an aortic valve
26 of the subject, such that a proximal end 28 of the tube is
disposed in an aorta 30 of the subject and a distal end 32 of the
tube is disposed within left ventricle 22. Tube 24 (which is
sometimes referred to herein as a "blood-pump tube") is typically
an elongate tube, an axial length of the tube typically being
substantially larger than its diameter. The scope of the present
invention includes using the apparatus and methods described herein
in anatomical locations other than the left ventricle and the
aorta. Therefore, the ventricular assist device and/or portions
thereof are sometimes referred to herein (in the specification and
the claims) as a blood pump.
[0216] For some applications, the ventricular assist device is used
to assist the functioning of a subject's left ventricle during a
percutaneous coronary intervention. In such cases, the ventricular
assist device is typically used for a period of up to 10 hours
(e.g., up to six hours), during a period in which there is risk of
developing hemodynamic instability (e.g., during or immediately
following the percutaneous coronary intervention). Alternatively or
additionally, the ventricular assist device is used to assist the
functioning of a subject's left ventricle for a longer period
(e.g., for example, 2-20 days, e.g., 4-14 days) upon a patient
suffering from cardiogenic shock, which may include any
low-cardiac-output state (e.g., acute myocardial infarction,
myocarditis, cardiomyopathy, post-partum, etc.). For some
applications, the ventricular assist device is used to assist the
functioning of a subject's left ventricle for yet a longer period
(e.g., several weeks or months), e.g., in a "bridge to recovery"
treatment. For some such applications, the ventricular assist
device is permanently or semi-permanently implanted, and the
impeller of the ventricular assist device is powered
transcutaneously, e.g., using an external antenna that is
magnetically coupled to the impeller.
[0217] As shown in FIG. 1B, which shows steps in the deployment of
the ventricular assist device in the left ventricle, typically the
distal end of the ventricular assist device is guided to the left
ventricle over a guidewire 10. During the insertion of the distal
end of the device to the left ventricle, a delivery catheter 143 is
disposed over the distal end of the device. Once the distal end of
the device is disposed in the left ventricle, the delivery catheter
is typically retracted to the aorta, and the guidewire is withdrawn
from the subject's body. The retraction of the delivery catheter
typically causes self-expandable components of the distal end of
the device to assume non-radially-constrained configurations, as
described in further detail hereinbelow. Typically, the ventricular
assist device is inserted into the subject's body in order to
provide an acute treatment to the subject. For some applications,
in order to withdraw the left ventricular device from the subject's
body at the end of the treatment, the delivery catheter is advanced
over the distal end of the device, which causes the self-expandable
components of the distal end of the device to assume
radially-constrained configurations. Alternatively or additionally,
the distal end of the device is retracted into the delivery
catheter which causes the self-expandable components of the distal
end of the device to assume radially-constrained
configurations.
[0218] For some applications (not shown), the ventricular assist
device and/or delivery catheter 143 includes an ultrasound
transducer at its distal end and the ventricular assist device is
advanced toward the subject's ventricle under ultrasound
guidance.
[0219] Referring now to FIG. 1C, which shows pump portion 27 of
ventricular assist device 20 in greater detail, typically, an
impeller 50 is disposed within a distal portion 102 of tube 24 and
is configured to pump blood from the left ventricle into the aorta
by rotating. The tube typically defines one or more blood inlet
openings 108 at the distal end of the tube, via which blood flows
into the tube from the left ventricle, during operation of the
impeller. For some applications, proximal portion 106 of the tube
defines one or more blood outlet openings 109, via which blood
flows from the tube into the ascending aorta, during operation of
the impeller.
[0220] For some applications, control console 21 (shown in FIG.
1A), which typically includes a computer processor 25, drives the
impeller to rotate. For example, the computer processor may control
a motor 74 (shown in FIG. 7), which is disposed within motor unit
23 (shown in FIG. 1A) and which drives the impeller to rotate via a
drive cable 130 (shown in FIG. 7). For some applications, the
computer processor is configured to detect a physiological
parameter of the subject (such as left-ventricular pressure,
cardiac afterload, rate of change of left-ventricular pressure,
etc.) and to control rotation of the impeller in response thereto,
as described in further detail hereinbelow. Typically, the
operations described herein that are performed by the computer
processor, transform the physical state of a memory, which is a
real physical article that is in communication with the computer
processor, to have a different magnetic polarity, electrical
charge, or the like, depending on the technology of the memory that
is used. Computer processor 25 is typically a hardware device
programmed with computer program instructions to produce a
special-purpose computer. For example, when programmed to perform
the techniques described herein, computer processor 25 typically
acts as a special-purpose, ventricular-assist computer processor
and/or a special-purpose, blood-pump computer processor.
[0221] For some applications, a purging system 29 (shown in FIG.
1A) drives a fluid (e.g., a glucose solution) to pass through
portions of ventricular assist device 20, for example, in order to
cool portions of the device and/or in order to wash debris from
portions of the device. Purging system 29 is described in further
detail hereinbelow.
[0222] Typically, along distal portion 102 of tube 24, a frame 34
is disposed within the tube around impeller 50. The frame is
typically made of a shape-memory alloy, such as nitinol. For some
applications, the shape-memory alloy of the frame is shape set such
that at least a portion of the frame (and thereby distal portion
102 of tube 24) assumes a generally circular, elliptical, or
polygonal cross-sectional shape in the absence of any forces being
applied to distal portion 102 of tube 24. By assuming its generally
circular, elliptical, or polygonal cross-sectional shape, the frame
is configured to hold the distal portion of the tube in an open
state. Typically, during operation of the ventricular assist
device, the distal portion of the tube is configured to be placed
within the subject's body, such that the distal portion of the tube
is disposed at least partially within the left ventricle.
[0223] For some applications, along proximal portion 106 of tube
24, the frame is not disposed within the tube, and the tube is
therefore not supported in an open state by frame 34. Tube 24 is
typically made of a blood-impermeable collapsible material. For
example, tube 24 may include polyurethane, polyester, and/or
silicone. Alternatively or additionally, the tube is made of
polyethylene terephthalate (PET) and/or polyether block amide
(e.g., PEBAX.RTM.). For some applications (not shown), the tube is
reinforced with a reinforcement structure, e.g., a braided
reinforcement structure, such as a braided nitinol tube. Typically,
the proximal portion of the tube is configured to be placed such
that it is at least partially disposed within the subject's
ascending aorta. For some applications, the proximal portion of the
tube traverses the subject's aortic valve, passing from the
subject's left ventricle into the subject's ascending aorta, as
shown in FIG. 1B. As described hereinabove, the tube typically
defines one or more blood inlet openings 108 at the distal end of
the tube, via which blood flows into the tube from the left
ventricle, during operation of the impeller. For some applications,
the proximal portion of the tube defines one or more blood outlet
openings 109, via which blood flows from the tube into the
ascending aorta, during operation of the impeller. Typically, the
tube defines a plurality of blood outlet openings 109, for example,
between two and eight blood outlet openings (e.g., between two and
four blood outlet openings). During operation of the impeller, the
pressure of the blood flow through the tube typically maintains the
proximal portion of the tube in an open state. For some
applications, in the event that, for example, the impeller
malfunctions, the proximal portion of the tube is configured to
collapse inwardly, in response to pressure outside of the proximal
portion of the tube exceeding pressure inside the proximal portion
of the tube. In this manner, the proximal portion of the tube acts
as a safety valve, preventing retrograde blood flow into the left
ventricle from the aorta.
[0224] Referring again to FIG. 1C, for some applications, frame 34
is shaped such that the frame defines a proximal conical portion
36, a central cylindrical portion 38, and a distal conical portion
40. Typically, the proximal conical portion is such that the narrow
end of the cone is proximal with respect to the wide end of the
cone. Further typically, the distal conical portion is such that
the narrow end of the cone is distal with respect to the wide end
of the cone. For some applications, tube 24 extends to the end of
cylindrical portion 38 (or slightly proximal or distal thereof),
such that the distal end of the tube defines a single
axially-facing blood inlet opening 108, as shown in FIG. 1C. For
some applications, within at least a portion of frame 34, an inner
lining 39 lines the frame, as described hereinbelow with reference
to FIGS. 19A-H. In accordance with respective applications, the
inner lining partially overlaps or fully overlaps with tube 24 over
the portion of the frame that the inner lining lines. For such
applications, the distal end of the inner lining defines a single
axially-facing blood inlet opening 108. For some applications (not
shown), tube 24 extends to the end of distal conical portion 40,
and the tube defines one or more lateral blood inlet openings (not
shown), e.g., as described in US 2019/0209758 to Tuval, which is
incorporated herein by reference. For such applications, the tube
typically defines two to four lateral blood inlet openings.
[0225] Typically, tube 24 includes a conical proximal portion 42
and a cylindrical central portion 44. The proximal conical portion
is typically such that the narrow end of the cone is proximal with
respect to the wide end of the cone. Typically, blood outlet
openings 109 are defined by tube 24, such that the openings extend
at least partially along the proximal conical section of tube 24.
For some such applications, the blood outlet openings are
teardrop-shaped, as shown in FIG. 1C. Typically, the
teardrop-shaped nature of the blood outlet openings in combination
with the openings extending at least partially along the proximal
conical section of tube 24 causes blood to flow out of the blood
outlet openings along flow lines that are substantially parallel
with the longitudinal axis of tube 24 at the location of the blood
outlet openings.
[0226] As described hereinabove, for some applications (not shown),
the tube extends to the end of distal conical portion 40 of frame
34. For such applications, the tube typically defines a distal
conical portion, with the narrow end of the cone being distal with
respect to the wide end of the cone. For some applications (not
shown), the diameter of tube 24 changes along the length of the
central portion of the tube, such that the central portion of the
tube has a frustoconical shape. For example, the central portion of
the tube may widen from its proximal end to is distal end, or may
narrow from its proximal end to its distal end. For some
applications, at its proximal end, the central portion of the tube
has a diameter of between 5 and 7 mm, and at its distal end, the
central portion of the tube has a diameter of between 8 and 12
mm.
[0227] Again referring to FIG. 1C, the ventricular assist device
typically includes a distal-tip element 107 that is disposed
distally with respect to frame 34 and that includes an
axial-shaft-receiving tube 126 and a distal-tip portion 120, both
of which are described in further detail hereinbelow.
[0228] Reference is now made to FIGS. 2A, 2B, 2C, 2D, 2E, and 2F,
which are schematic illustrations of frame 34 that houses an
impeller of ventricular assist device 20, in accordance with some
applications of the present invention. As described hereinabove,
frame 34 is typically made of a shape-memory alloy, such as
nitinol, and the shape-memory alloy of the frame is shape set such
that the frame (and thereby tube 24) assumes a generally circular,
elliptical, or polygonal cross-sectional shape in the absence of
any forces being applied to tube 24. By assuming its generally
circular, elliptical, or polygonal cross-sectional shape, the frame
is configured to hold the distal portion of the tube in an open
state.
[0229] Typically, the frame is a stent-like frame, in that it
comprises struts that, in turn, define cells. Further typically,
the frame is covered with tube 24, and/or covered with an inner
lining 39, described hereinbelow, with reference to FIGS. 19A-H. As
described hereinbelow, for some applications impeller 50 undergoes
axial back-and-forth motion with respect to frame 34. Typically
over the course of the motion of the impeller with respect to the
frame the location of the portion of the impeller that defines the
maximum span of the impeller is disposed within cylindrical portion
38 of frame 34. In some cases, if the cells of the cylindrical
portion 38 of frame 34 are too large, then tube 24, and/or inner
lining 39 gets stretched between edges of the cells, such that the
tube 24, and/or inner lining 39 does not define a circular
cross-section. For some applications, if this occurs in the region
in which the portion of the impeller that defines the maximum span
of the impeller is disposed, this results in a non-constant gap
between the edges of the impeller blades and tube 24 (and/or inner
lining) at that location, over the course of a rotation cycle of
the impeller. For some applications, this may lead to increased
hemolysis relative to if there were a constant gap between the
edges of the impeller blades and tube 24 (and/or inner lining) at
that location, over the course of the rotation cycle of the
impeller.
[0230] Referring to FIG. 2A, at least partially in view of the
issues described in the above paragraph, within cylindrical portion
38 of frame 34, the frame defines a large number of relatively
small cells. Typically, when the frame is disposed in its
non-radially-constrained configuration, the maximum cell width CW
of the each of the cells (i.e., the distance from the inner edge of
the strut at the central junction on one side of the cell to the
inner edge of the strut at the central junction on the other side
of the cell, as measured around the circumference of cylindrical
portion 38) within the cylindrical portion of the frame is less
than 2 mm, e.g., between 1.4 mm and 1.6 mm, or between 1.6 and 1.8
mm. Since the cells are relatively small, the tube 24 (and/or inner
lining) defines a substantially circular cross-section within the
cylindrical portion of the frame.
[0231] Still referring to FIG. 2A, and starting from the proximal
end of the frame (which is to the left of the figure), typically
the frame defines the following portions (a) coupling portion 31
via which the frame is coupled to a proximal bearing 116 (shown in
FIG. 4) of the ventricular assist device, (b) proximal conical
portion 36, (c) cylindrical portion 38, (d) distal conical portion
40, and (e) distal strut junctions 33. As illustrated, as the frame
transitions from a proximal end of the frame toward the center of
the frame (e.g., as the frame transitions through coupling portion
31, through proximal conical portion 36, and to cylindrical portion
38), struts 37 of the frame pass through junctions 35, at which the
two struts branch from a single strut, in a Y-shape. As described
in further detail hereinbelow, typically frame 34 is placed in a
radially-constrained (i.e., crimped) configuration within delivery
catheter 143 by the frame being axially elongated. Moreover, the
frame typically transmits its radial narrowing to the impeller, and
the impeller becomes radially constrained by becoming axially
elongated within the frame. For some applications, the struts of
the frame being configured in the manner described above
facilitates transmission of axial elongation from the delivery
catheter (or other device that is configured to crimp the frame) to
the frame, which in turn facilitates transmission of axial
elongation to the impeller. This is because the pairs of struts
that branch from each of junctions 35 are configured to pivot about
the junction and move closer to each other such as to close.
[0232] Still referring to FIG. 2A, for some applications distal
strut junctions 33 are maintained in open states when the frame is
coupled to axial shaft 92 (shown in FIG. 2D), in order for the
impeller to be placed within the frame via the distal end of the
frame. Subsequently, the distal strut portions are closed around
the outside of a distal bearing 118, as described in further detail
hereinbelow with reference to FIGS. 5A-B. For some applications, a
proximal end of distal-tip element 107 (shown in FIG. 1C) holds the
distal strut portions in their closed configurations around the
outside of distal bearing 118.
[0233] Typically, when disposed in its non-radially-constrained
configuration, frame 34 has a total length of more than 25 mm
(e.g., more than 30 mm), and/or less than 50 mm (e.g., less than 45
mm), e.g., 25-50 mm, or 30-45 mm. Typically, when disposed in its
radially-constrained configuration (within delivery catheter 143),
the length of the frame increases by between 2 and 5 mm. Typically,
when disposed in its non-radially-constrained configuration, the
cylindrical portion of frame 34 has a length of more than 10 mm
(e.g., more than 12 mm), and/or less than 25 mm (e.g., less than 20
mm), e.g., 10-25 mm, or 12-20 mm. For some applications, a ratio of
the length of the cylindrical portion of the frame to the total
length of the frame is more than 1:4 and/or less than 1:2, e.g.,
between 1:4 and 1:2.
[0234] Reference is now made to FIG. 2B, which is a schematic
illustration of a pump portion of ventricular assist device 20, at
least a portion of cylindrical portion 38 of frame 34 of the
ventricular assist device having a helical structure 55, in
accordance with some applications of the present invention. For
some applications, at least a portion of cylindrical portion 38 of
frame 34 of the ventricular assist device has a helical structure
55, in order for the tube 24 (and/or inner lining) to define a
substantially circular cross-section within the cylindrical portion
of the frame, e.g., for the reasons provided hereinabove.
[0235] Reference is now made to FIG. 2C, which is a schematic
illustration of frame 34, the frame transitioning from its ends to
its maximum diameter (i.e., the cylindrical portion of the frame)
over a relatively short distance D. Typically, this results in the
ratio of the cylindrical portion of the frame to the total length
of the frame being greater than that described hereinabove. For
example, the ratio of the cylindrical portion of the frame to the
total length of the frame may be more than 1:2 or more than 2:3.
Further typically, this results in the angle at which the frame
widens within the conical portion being greater than if the
cylindrical portion has a shorter relative length, ceteris paribus.
For some applications, in turn, this reduces vibration of the frame
during rotation of the impeller. As described hereinabove, in order
to reduce hemolysis, it is typically desirable to maintain a
constant gap between the edges of the impeller blades and tube 24
(and/or inner lining 39). Therefore, it is typically desirable to
reduce vibration of the frame with respect to the impeller.
[0236] Reference is now made to FIG. 2D, which is a schematic
illustration of a pump portion of a ventricular assist device that
includes an inflatable impeller housing 60, in accordance with some
applications of the present invention. For some applications,
rather than having frame 34 surrounding the impeller, the
inflatable housing surrounds the impeller. For some applications,
at least in the region of the housing that surrounds the impeller,
the frame is configured to define an inner circular cross-section,
such that there is a constant gap between the edges of the impeller
blades and the inner wall of the housing, over the course of the
rotation cycle of the impeller.
[0237] Typically, for applications as shown in FIG. 2D, proximal
and distal bearing frames 61 are disposed inside the inflatable
impeller housing. The bearing frames are configured to act as
radial bearings with respect to axial shaft 92 (described
hereinbelow) to which impeller 50 is coupled. For some
applications, the impeller housing is made of a flexible and
inflatable material. The impeller housing is typically inserted
into the left ventricle in a deflated state, and is inflated once
disposed inside the left ventricle, such as to assume its deployed
shape. Tube 24 typically extends proximally from the inflatable
impeller housing. For some applications, tubes 63 pass along tube
24 (e.g., an inner surface or an outer surface of the tube), and
the inflatable housing is inflated via the tubes. For some
applications, the impeller housing is inflated with saline and/or a
different solution (e.g., a glucose solution). For some
applications, the inflatable impeller housing defines one or more
blood inlet openings 108.
[0238] Reference is now made to FIGS. 2E and 2F, which are
schematic illustrations of flattened profiles of frame 34, the
frame being generally configured as shown in FIG. 2A, in accordance
with some applications of the present invention. Frame 34 is
typically laser cut from a tube of a shape memory alloy, such as
nitinol. The profiles shown in FIGS. 2E and 2F depict (for
illustrative purposes) how the frame of the device would appear if,
prior to shape setting the frame, a longitudinal incision were to
be made along the length of the frame at a given circumferential
location of the frame, and the frame were to then be laid out flat
upon a surface. For some applications, within cylindrical portion
38 of the frame, the cells are cut by passing a laser along the
outlines of the perimeter of the cells, as indicated by the
enlarged portion of FIG. 2E. As described hereinabove, typically,
within the cylindrical portion the cells are relatively small,
which means that a relatively large number of cells are cut within
the circumference of the frame. Due to the size of the laser that
is used for cutting the cells, it can be challenging passing the
laser around the full perimeter of the cells. However, in the
vicinity of the junctions it is desirable for the cells to be
rounded, in order to reduce strain at the junctions. Therefore, for
some applications, the cylindrical portion of the frame is cut as
generally shown in FIG. 2F. Namely, at junctions 35, the laser cuts
rounded edges 41. However, between the junctions, the laser cuts a
single slit 43, rather than cutting around the perimeter of the
cell.
[0239] Reference is now made to FIGS. 3A-C, which are schematic
illustrations of impeller 50 or portions thereof, in accordance
with some applications of the present invention. Typically, the
impeller includes at least one outer helical elongate element 52,
which winds around a central axial spring 54, such that the helix
defined by the helical elongate element is coaxial with the central
axial spring. Typically, the impeller includes two or more helical
elongate elements (e.g., three helical elongate elements, as shown
in FIGS. 3A-C). For some applications, the helical elongate
elements and the central axial spring are made of a shape-memory
material, e.g., a shape-memory alloy such as nitinol. Typically,
each of the helical elongate elements and the central axial spring
support a film 56 of a material (e.g., an elastomer, such as
polyurethane, and/or silicone) therebetween. For some applications,
the film of material includes pieces of nitinol embedded therein,
for example in order to strengthen the film of material. For
illustrative purposes, the impeller is shown in the absence of the
material in FIG. 3A. FIGS. 3B and 3C show respective views of the
impeller with the material supported between the helical elongate
elements and the spring.
[0240] Each of the helical elongate elements, together with the
film extending from the helical elongate element to the spring,
defines a respective impeller blade, with the helical elongate
elements defining the outer edges of the blades, and the axial
spring defining the axis of the impeller. Typically, the film of
material extends along and coats the spring. For some applications,
sutures 53 (e.g., polyester sutures, shown in FIGS. 3B and 3C) are
wound around the helical elongate elements, e.g., as described in
US 2016/0022890 to Schwammenthal, which is incorporated herein by
reference. Typically, the sutures are configured to facilitate
bonding between the film of material (which is typically an
elastomer, such as polyurethane, or silicone) and the helical
elongate element (which is typically a shape-memory alloy, such as
nitinol). For some applications, sutures (e.g., polyester sutures,
not shown) are wound around spring 54. Typically, the sutures are
configured to facilitate bonding between the film of material
(which is typically an elastomer, such as polyurethane, or
silicone) and the spring (which is typically a shape-memory alloy,
such as nitinol).
[0241] Enlargements A and B of FIG. 3C show two alternative ways in
which the sutures are tied around helical elongate elements 52. For
some applications, the sutures are tied around the outer surface of
the helical elongate elements, as shown in enlargement A.
Alternatively, the helical elongate elements define grooves 45 on
their outer surfaces, and the sutures are embedded within the
grooves, as shown in enlargement B. By embedding the sutures within
the grooves, the sutures typically do not add to the outer profile
of the impeller, and the outer profile of the impeller is defined
by the outer surfaces of the helical elongate elements.
[0242] Typically, proximal ends of spring 54 and helical elongate
elements 52 extend from a proximal bushing (i.e., sleeve bearing)
64 of the impeller, such that the proximal ends of spring 54 and
helical elongate elements 52 are disposed at a similar radial
distance from the longitudinal axis of the impeller, as each other.
Similarly, typically, distal ends of spring 54 and helical elongate
elements 52 extend from a distal bushing 58 of the impeller, such
that the distal ends of spring 54 and helical elongate elements 52
are disposed at a similar radial distance from the longitudinal
axis of the impeller, as each other. Typically, spring 54, as well
as proximal bushing 64 and distal bushing 58 of the impeller,
define a lumen 62 therethrough (shown in FIG. 3C).
[0243] Reference is now made to FIG. 4, which is a schematic
illustration of impeller 50 disposed inside frame 34 of ventricular
assist device 20, in accordance with some applications of the
present invention. For some applications, within at least a portion
of frame 34, an inner lining 39 lines the frame, as described
hereinbelow with reference to FIGS. 19A-H. In accordance with
respective applications, the inner lining partially overlaps or
fully overlaps with tube 24 over the portion of the frame that the
inner lining lines. In the application shown in FIG. 4, the inner
lining lines the inside of the cylindrical portion of the frame and
tube 24 does not cover the cylindrical portion of the frame.
However, the scope of the present application includes applying the
apparatus and methods described with reference to FIG. 4 to any one
of the applications described hereinbelow with reference to FIGS.
19A-H.
[0244] As shown in FIG. 4, typically there is a gap G, between the
outer edge of impeller 50 and inner lining 39, even at a location
at which the span of the impeller is at its maximum. For some
applications, it is desirable that the gap between the outer edge
of the blade of the impeller and the inner lining 39 be relatively
small, in order for the impeller to efficiently pump blood from the
subject's left ventricle into the subject's aorta. However, it is
also desirable that a gap between the outer edge of the blade of
the impeller and the inner surface of frame 34 be maintained
substantially constant throughout the rotation of the impeller
within frame 34, for example, in order to reduce the risk of
hemolysis.
[0245] For some applications, when the impeller and frame 34 are
both disposed in non-radially-constrained configurations, gap G
between the outer edge of the impeller and the inner lining 39, at
the location at which the span of the impeller is at its maximum,
is greater than 0.05 mm (e.g., greater than 0.1 mm), and/or less
than 1 mm (e.g., less than 0.4 mm), e.g., 0.05-1 mm, or 0.1-0.4 mm.
For some applications, when the impeller is disposed in its
non-radially-constrained configurations, the outer diameter of the
impeller at the location at which the outer diameter of the
impeller is at its maximum is more than 7 mm (e.g., more than 8
mm), and/or less than 10 mm (e.g., less than 9 mm), e.g., 7-10 mm,
or 8-9 mm. For some applications, when frame 34 is disposed in its
non-radially-constrained configuration, the inner diameter of frame
34 (as measured from the inside of inner lining 39 on one side of
the frame to the inside of inner lining on the opposite side of the
frame) is greater than 7.5 mm (e.g., greater than 8.5 mm), and/or
less than 10.5 mm (e.g., less than 9.5 mm), e.g., 7.5-10.5 mm, or
8.5-9.5 mm. For some applications, when the frame is disposed in
its non-radially-constrained configuration, the outer diameter of
frame 34 is greater than 8 mm (e.g., greater than 9 mm), and/or
less than 13 mm (e.g., less than 12 mm), e.g., 8-13 mm, or 9-12
mm.
[0246] Typically, an axial shaft 92 passes through the axis of
impeller 50, via lumen 62 of the impeller. Further typically, the
axial shaft is rigid, e.g., a rigid tube. For some applications,
proximal bushing 64 of the impeller is coupled to the shaft such
that the axial position of the proximal bushing with respect to the
shaft is fixed, and distal bushing 58 of the impeller is slidable
with respect to the shaft. The axial shaft itself is radially
stabilized via a proximal radial bearing 116 and a distal radial
bearing 118. In turn, the axial shaft, by passing through lumen 62
defined by the impeller, radially stabilizes the impeller with
respect to the inner surface of frame 34, such that even a
relatively small gap between the outer edge of the blade of the
impeller and the inner surface of frame 34 (e.g., a gap that is as
described above) is maintained, during rotation of the
impeller.
[0247] Referring again to FIGS. 3A-C, for some applications, the
impeller includes a plurality of elongate elements 67 extending
radially from central axial spring 54 to outer helical elongate
elements 52. The elongate elements are typically flexible but are
substantially non-stretchable along the axis defined by the
elongate elements. Further typically, each of the elongate elements
is configured not to exert force upon the helical elongate element,
unless force is acting upon the impeller that is causing the
helical elongate element to move radially outward, such that (in
the absence of the elongate element) a separation between the
helical elongate element and the central axial spring would be
greater than a length of the elongate element. For example, the
elongate elements may include strings (such as polyester, and/or
another polymer or a natural material that contains fibers) and/or
wires (such as nitinol wires, and/or wires made of a different
alloy, or a metal).
[0248] For some applications, the elongate elements 67 maintain the
helical elongate element (which defines the outer edge of the
impeller blade) within a given distance with respect to the central
axial spring. In this manner, the elongate elements are configured
to prevent the outer edge of the impeller from being forced
radially outward due to forces exerted upon the impeller during the
rotation of the impeller. The elongate elements are thereby
configured to maintain the gap between the outer edge of the blade
of the impeller and the inner surface of frame 34, during rotation
of the impeller. Typically, more than one (e.g., more than two)
and/or fewer than eight (e.g., fewer than four) elongate elements
67 are used in the impeller, with each of the elongate elements
typically being doubled (i.e., extending radially from central
axial spring 54 to an outer helical elongate element 52, and then
returning from the helical elongate element back to the central
axial spring). For some applications, a plurality of elongate
elements, each of which extends from the spring to a respective
helical elongate element and back to the spring, are formed from a
single piece of string or a single wire, as described in further
detail hereinbelow.
[0249] For some applications, the impeller is manufactured in the
following manner. Proximal bushing 64, distal bushing 58, and
helical elongate elements 52 are cut from a tube of shape-memory
material, such as nitinol. The cutting of the tube, as well as the
shape setting of the shape-memory material, is typically performed
such that the helical elongate elements are defined by the
shape-memory material, e.g., using generally similar techniques to
those described in US 2016/0022890 to Schwammenthal. Typically,
spring 54 is inserted into the cut and shape-set tube, such that
the spring extends along the length of the tube from at least the
proximal bushing to the distal bushing. For some applications, the
spring is inserted into the cut and shape-set tube while the spring
is in an axially compressed state, and the spring is configured to
be held in position with respect to the tube, by exerting a radial
force upon the proximal and distal bushings. Alternatively or
additionally, portions of the spring are welded to the proximal and
distal bushings. For some applications, the spring is cut from a
tube of a shape-memory material, such as nitinol. For some such
applications, the spring is configured such that, when the spring
is disposed in a non-radially-constrained configuration (in which
the spring is typically disposed during operation of the impeller),
there are substantially no gaps between windings of the spring and
adjacent windings thereto.
[0250] For some applications, subsequent to spring 54 being
inserted into the cut and shape-set tube, elongate elements 67, as
described hereinabove, are placed such as to extend between the
spring and one or more of the helical elongate elements, for
example, in the following manner. A mandrel (e.g., a polyether
ether ketone (PEEK) and/or a polytetrafluoroethylene (PTFE)
mandrel) is inserted through the lumen defined by the spring and
the bushings. A string or a wire is then threaded such that it
passes (a) from the mandrel to a first one of the helical elongate
elements, (b) back from the first of the helical elongate elements
to the mandrel, (c) around the mandrel, and to a second one of the
helical elongate elements, (d) back from the second one of the
helical elongate elements to the mandrel, etc. Once the string or
the wire has been threaded from the mandrel to each of the helical
elongate elements and back again, the ends of the string or the
wire are coupled to each other, e.g., by tying them to each other.
For some applications, sutures 53 (e.g., polyester sutures) are
wound around the helical elongate elements, in order to facilitate
bonding between the film of material (which is typically an
elastomer, such as polyurethane, or silicone) and the helical
elongate elements (which is typically a shape-memory alloy, such as
nitinol), in a subsequent stage of the manufacture of the impeller.
For some applications, sutures (e.g., polyester sutures, not shown)
are wound around spring 54. Typically, the sutures are configured
to facilitate bonding between the film of material (which is
typically an elastomer, such as polyurethane, or silicone) and the
spring (which is typically a shape-memory alloy, such as nitinol),
in the subsequent stage of the manufacture of the impeller.
[0251] Typically, at this stage, a structure 59 has been assembled
that is as shown in FIG. 3A. The structure includes the cut and
shape-set tube that defines the proximal and distal bushings, the
helical elongate elements, and the spring (and, optionally, the
elongate elements, and the sutures). This structure is dipped into
the material that defines film 56. For some applications, the
assembled structure is dipped into the material with the mandrel
disposed through the lumen defined by the spring and the bushings,
although it is noted that the mandrel is not shown in FIG. 3A.
Typically, the material from which the film is made is silicone
and/or polyurethane (and/or a similar elastomer), and the assembled
structure is dipped into the material, while the material is in an
uncured, liquid state. Subsequently, the material is cured such
that it solidifies, e.g., by being left to dry. Once the material
has dried, the mandrel is typically removed from the lumen defined
by the bushings and the spring.
[0252] The result of the process described above is typically that
there is a continuous film of material extending between each of
the helical elongate elements to the spring, and also extending
along the length of the spring, such as to define a tube, with the
spring embedded within the tube. The portions of the film that
extend from each of the helical elongate elements to the spring
define the impeller blades. For applications in which the impeller
includes elongate elements 67, the elongate elements are typically
embedded within these portions of film.
[0253] Typically, impeller 50 is inserted into the left ventricle
transcatheterally, while impeller 50 is in a radially-constrained
configuration. In the radially-constrained configuration, both
helical elongate elements 52 and central axial spring 54 become
axially elongated, and radially constrained. Typically film 56 of
the material (e.g., silicone and/or polyurethane) changes shape to
conform to the shape changes of the helical elongate elements and
the axial support spring, both of which support the film of
material. Typically, using a spring to support the inner edge of
the film allows the film to change shape without the film becoming
broken or collapsing, due to the spring providing a large surface
area to which the inner edge of the film bonds. For some
applications, using a spring to support the inner edge of the film
reduces a diameter to which the impeller can be radially
constrained, relative to if, for example, a rigid shaft were to be
used to support the inner edge of the film, since the diameter of
the spring itself can be reduced by axially elongating the
spring.
[0254] As described hereinabove, for some applications, proximal
bushing 64 of impeller 50 is coupled to axial shaft 92 such that
the axial position of the proximal bushing with respect to the
shaft is fixed, and distal bushing 58 of the impeller is slidable
with respect to the shaft. For some applications, when the impeller
is radially constrained for the purpose of inserting the impeller
into the ventricle or for the purpose of withdrawing the impeller
from the subject's body, the impeller axially elongates by the
distal bushing sliding along the axial shaft distally. Subsequent
to being released inside the subject's body, the impeller assumes
its non-radially-constrained configuration (in which the impeller
is typically disposed during operation of the impeller), as shown
in FIGS. 3A-C.
[0255] It is noted that, for illustrative purposes, in some of the
figures, impeller 50 is shown without including all of the features
of the impeller as shown and described with respect to FIGS. 3A-C.
For example, some of the figures show the impeller not including
sutures 53 and/or elongate elements 67. The scope of the present
application includes using an impeller with any of the features
shown and described with respect to FIGS. 3A-C in combination with
any of the apparatus and methods described herein.
[0256] Reference is now made to FIGS. 3D, 3E, and 3F, which are
schematic illustration of impeller 50 or portions thereof, in
accordance with some applications of the present invention. As
described hereinabove, for some applications, impeller 50 includes
sutures 53. Sutures 53 are wound around the helical elongate
elements 52 and are configured to facilitate bonding between the
film of material (which is typically an elastomer, such as
polyurethane, or silicone) and the helical elongate element (which
is typically a shape-memory alloy, such as nitinol).
[0257] As an alternative or in addition to sutures 53, for some
applications, coils 68 are wound around (or placed over) the
helical elongate elements, as shown in FIG. 3D. For example, a
tightly-wound coil (e.g., a tightly-wound nitinol coil) may be
wound around (or placed around) each of the helical elongate
elements. The coil typically facilitates bonding between the film
of material and the helical elongate element by increasing the
surface area to which the material bonds at the interface between
the material and the helical elongate element. For some
applications, structure 59 is formed modularly (e.g., as described
hereinbelow with reference to FIG. 3F.) For some such applications,
the coils are placed around each of the elongate elements 52 (e.g.,
by sliding the entire coil over the elongate element in a single
action), prior to the elongate elements being coupled to the
proximal and distal bushings of the impeller.
[0258] As a further alternative to or in addition to sutures 53,
for some applications, sleeves 69 are placed around the helical
elongate elements, as shown in FIG. 3E. For example, such sleeves
may be made of a polymer, such as polyester. The sleeves typically
facilitate bonding between the film of material and the helical
elongate elements by increasing the surface area to which the
material bonds at the interfaces between the material and the
helical elongate elements. For some applications, the sleeve acts
as a mediator between a material from which the elongate elements
are made, which typically has a relatively high stiffness (and is
typically nitinol), and the material from which film 56 is made,
which is typically an elastomer having a relatively low stiffness.
The sleeve thereby enhances the strength of the coupling between
the material and the helical elongate elements, when the material
dries. For some applications, sleeves 69 are applied to structure
59. For some such applications, longitudinal slits are formed in
the sleeves in order to allow the sleeves to be placed around the
helical elongate elements 52. Subsequent to being placed around
helical elongate elements 52 the slits are closed (e.g., by
suturing or adhering the slits closed). For some applications,
structure 59 is formed modularly (e.g., as described hereinbelow
with reference to FIG. 3F.) For some such applications, the sleeves
are placed around elongate elements 52, prior to the elongate
elements being coupled to the proximal and distal bushings of the
impeller.
[0259] As yet a further alternative to or in addition to sutures
53, for some applications, elongate elements 52 are shaped to have
a rounded (e.g., a circular) cross section, as shown in the right
portion of FIG. 3F (which shows a cross-sectional view of an
elongate element having a rounded cross-section). The left portion
of FIG. 3F shows a cross-sectional view of elongate element 52 with
material of film 56 coupled to the elongate element, in a case in
which the elongate element has a non-rounded cross section (e.g., a
square or a rectangular cross section). As shown, it is sometimes
the case that the material (e.g., the silicone and/or the
polyurethane) from which the film is made forms a thinner layer at
the corners of an elongate element having a non-rounded
cross-section. By contrast as shown in the left portion of FIG. 3F,
when the elongate element has a rounded cross section, the material
typically forms a layer having a substantially uniform thickness at
the interface with the elongate element. Therefore, for some
applications, the elongate elements have rounded cross
sections.
[0260] For some applications, proximal and distal bushings 64, 58
and elongate elements 52 are cut from an alloy tube, e.g., as
described hereinabove. For such applications, after the tube is
cut, the elongate elements typically have non-rounded edges.
Therefore for some applications, subsequent to the tube being cut,
the edges of the elongate elements are rounded, for example, using
grinding, sandblasting, tumble finishing, etching, plasma,
surface-charging, and/or by adding rounded edges to the elongate
elements. Alternatively, the proximal and distal bushings and the
elongate elements may be formed in a modular manner, and may
subsequently be coupled to each other (e.g., via welding, and/or
swaging). For some such applications, the elongate elements that
are coupled to the proximal and distal bushings have rounded cross
sections. As described hereinabove with reference to FIG. 3E, for
some applications, sleeves 69 are placed on the elongate elements
prior to the elongate elements being coupled to the proximal
bushing and/or prior to the elongate elements being coupled to the
distal bushing.
[0261] For some applications, alternative or additional techniques
are used to facilitate bonding between the film of material and the
helical elongate elements. For example, the helical elongate
elements may be treated using a surface treatment (such as,
grinding, sandblasting, tumble finishing, etching, plasma,
surface-charging, etc.), in order to roughen the outer surface of
the helical elongate elements.
[0262] In accordance with the above description of FIGS. 3A-F, for
some applications of the present invention, impeller 50 is
manufactured by forming a structure having first and second
bushings 64, 58 at proximal and distal ends of the structure, the
first and second bushings being connected to one another by at
least one elongate element 52. The at least one elongate element is
made to radially expand and form at least one helical elongate
element, at least partially by axially compressing the structure.
An elastomeric material is coupled to the at least one helical
elongate element, such that the at least one helical elongate
element with the elastomeric material coupled thereto defines a
blade of the impeller. Typically, the coupling is performed such
that a layer of the material is disposed around a radially outer
edge of the at least one helical elongate element, the layer of
material forming the effective edge of the impeller blade (i.e.,
the edge at which the impeller's blood-pumping functionality
substantially ceases to be effective). Further typically, the
method includes performing a step to enhance bonding of the
elastomeric material to the at least one helical elongate element
in a manner that does not cause a protrusion from the effective
edge of the impeller blade. For example, sutures 53 may be placed
within grooves defined by the at least one helical elongate
element, such that the sutures do not protrude from the radially
outer edge of the helical elongate element, the sutures being
configured to enhance bonding of the elastomeric material to the at
least one helical elongate element. Alternatively or additionally,
tightly-wound coil 68 may be placed around the at least one helical
elongate element, such that the elastomeric material forms a
substantially smooth layer along a radially outer edge of the coil,
the coil being configured to enhance bonding of the elastomeric
material to the at least one helical elongate element. Further
alternatively or additionally, sleeve 69 may be placed around the
at least one helical elongate element, such that the elastomeric
material forms a substantially smooth layer along a radially outer
edge of the sleeve, the sleeve being configured to enhance bonding
of the elastomeric material to the at least one helical elongate
element. For some applications, a rounded cross section is provided
to the at least one helical elongate element, such that the
elastomeric material forms a layer having a substantially uniform
thickness at an interface of the elastomeric material with the
helical elongate element. As noted hereinabove, it is typically
desirable that gap G between the outer edge of the blade of the
impeller and the inner lining 39 (shown in FIG. 4) be relatively
small. Therefore, it is desirable that there be no protrusion from
the effective edge of the impeller blade, since this would occupy
some of the gap between the outer edge of the impeller blade
(thereby requiring a larger gap), without increasing the
effectiveness of the blood-pumping functionality of the
impeller.
[0263] Reference is now made to FIGS. 3G and 3H, which are
schematic illustrations of elongate elements 67 extending between
each of the helical elongate elements 52 and spring 54, in
accordance with some applications of the present invention. For
some applications, a respective looped elongate element 67 extends
between each of the helical elongate elements and the spring.
Typically, the looped elongate elements are closed loops that have
predefined lengths and are (substantially) non-stretchable. The
lengths of the looped elongate elements are typically predefined,
such as to maintain the helical elongate element (which defines the
outer edge of the impeller blade) within a given distance with
respect to the central axial spring, and to thereby maintain the
gap between the outer edge of the blade of the impeller and the
inner surface of frame 34, during rotation of the impeller, as
described hereinabove. For some applications, the impeller is
formed by looping first ends of the looped elongate elements around
each of the helical elongate elements as indicated in the enlarged
portions of FIGS. 3G and 3H. Subsequently, spring 54 is inserted
through proximal and distal bushings 64, 58, and through second
ends of the looped helical elongate elements.
[0264] For some applications, at a longitudinally-central location
of spring 54, the spring is shaped to define a tube 70 (i.e.,
without windings), as shown in FIGS. 3G and 3H. Typically, the
second ends of the looped elongate elements loop around the tube at
the longitudinally-central location of the spring. Typically, this
reduces a risk of the looped elongate elements tearing, relative to
if the second ends of the looped elongate elements were to loop
around windings of the spring. For some applications (not shown),
the tube defines a groove therein and the second ends of the looped
elongate elements are configured to be held within the groove.
[0265] For some applications, the looped elongate element is looped
around the body of the helical elongate element, as shown in the
enlarged portions of FIG. 3G. Enlargements A and B of FIG. 3G show
two alternative ways in which the looped elongate element is looped
around the body of the helical elongate element. For some
applications, looped elongate element is looped around the outer
surface of the helical elongate element, as shown in enlargement A.
Alternatively, the helical elongate elements define grooves 45 on
their outer surfaces, and the looped elongate element is looped
around a groove 45 (such as to become embedded within the groove),
as shown in enlargement B. By embedding the looped elongate element
within the grooves, the looped elongate element typically does not
add to the outer profile of the impeller, and the outer profile of
the impeller is defined by the outer surfaces of the helical
elongate elements.
[0266] For some applications, the helical elongate element is
shaped to define two holes 71 disposed in close proximity to each
other, and the looped elongate element may be looped through the
holes, as shown in the enlarged portions of FIG. 3H. Enlargements A
and B of FIG. 3H show two alternative ways in which the looped
elongate element is looped through holes 71. For some applications,
the looped elongate element is looped around the outer surface of
the helical elongate element and through holes 71, as shown in
enlargement A. Alternatively, the helical elongate elements define
grooves 45 on their outer surfaces, and the looped elongate element
is looped around groove 45 and through holes 71 (such as to become
embedded within the groove), as shown in enlargement B. By
embedding the looped elongate element within the grooves, the
looped elongate element typically does not add to the outer profile
of the impeller, and the outer profile of the impeller is defined
by the outer surfaces of the helical elongate elements.
[0267] Referring now to FIGS. 3I, 3J, and 3K, for some
applications, structure 59 is configured to provide a relatively
long effective maximum-span length EML, the effective maximum-span
length EML being defined as the axial length along which the span
of the impeller is at its maximum. Typically, increasing the
effective maximum-span length EML of the impeller increases the
efficiency of the impeller (i.e., the amount of flow generated by
the impeller at a given rotation rate). For some applications, the
angle rho that the leading edge of the impeller blade makes with
respect to the longitudinal axis of the impeller is greater than 45
degrees, e.g., between 45 degrees and 70 degrees. As may be
observed by comparing FIG. 3J to FIG. 3I, ceteris paribus,
increasing angle rho increases the effective maximum-span length
EML, even if the overall length of the impeller is not increased.
Alternatively, the effective maximum-span length EML of the
impeller is increased by making the impeller longer, as shown in
FIG. 3K.
[0268] Reference is now made to FIGS. 5A and 5B, which are
schematic illustrations of impeller 50 and frame 34 of ventricular
assist device 20, respectively in non-radially-constrained and
radially-constrained states thereof, in accordance with some
applications of the present invention. The impeller and the frame
are typically disposed in the radially-constrained states during
the transcatheteral insertion of the impeller and the frame into
the subject's body, and are disposed in the
non-radially-constrained states during operation of the impeller
inside the subject's left ventricle. As described hereinabove,
typically tube 24 is disposed over at least some of the frame and
extends proximally therefrom. However, for illustrative purposes,
the frame and the impeller are shown in the absence of tube 24 in
FIGS. 5A-B.
[0269] As indicated in FIG. 5B, the frame and the impeller are
typically maintained in radially-constrained configurations by
delivery catheter 143. Typically, in the radially-constrained
configuration of the impeller the impeller has a total length of
more than 15 mm (e.g., more than 20 mm), and/or less than 30 mm
(e.g., less than 25 mm), e.g., 15-30 mm, or 20-25 mm. Further
typically, in the non-radially-constrained configuration of the
impeller, the impeller has a length of more than 8 mm (e.g., more
than 10 mm), and/or less than 18 mm (e.g., less than 15 mm), e.g.,
8-18 mm, or 10-15 mm. Still further typically, when the impeller
and frame 34 are disposed in radially-constrained configurations
(as shown in FIG. 5B), the impeller has an outer diameter of less
than 2 mm (e.g., less than 1.6 mm) and the frame has an outer
diameter of less than 2.5 mm (e.g., less than 2.1 mm).
[0270] Reference is also made to FIG. 5C, which shows a typical
bearing assembly that is used in prior art axial impeller-based
blood pumps. FIG. 5C is shown for the purpose of acting as a point
of reference for some of the applications of the invention
described herein. As shown in FIG. 5C, a bearing assembly typically
includes a radial bearing (indicated by ellipse 200) and a thrust
bearing (indicated by circle 202). The radial bearing is configured
to reduce radial motion of the impeller, by maintaining the axis of
the impeller at a given radial position. In response to an impeller
pumping blood in a first direction, forces acting upon the impeller
typically push the impeller to move in the opposite direction to
the first direction. The purpose of a thrust bearing is to oppose
such motion of the impeller and to maintain the axial position of
the impeller. In the example shown in FIG. 5C, in response to the
impeller pumping blood in the direction of arrow 204, the impeller
gets pushed in the direction of arrow 206, and the thrust bearing
opposes this motion. Typically, due to the frictional forces that
are exerted upon them, bearings undergo a substantial amount of
heating and wear. Thrust bearings are typically exposed to
substantial heating and wear, due to the fact that the frictional
forces that are exerted upon them are typically spread over
opposing surfaces having a smaller contact area between them, than
is the case for radial bearings.
[0271] As described hereinabove, typically, axial shaft 92 passes
through the axis of impeller 50, via lumen 62 of the impeller.
Typically, proximal bushing 64 of the impeller is coupled to the
shaft via a coupling element 65 such that the axial position of the
proximal bushing with respect to the shaft is fixed, and distal
bushing 58 of the impeller is slidable with respect to the shaft.
The axial shaft itself is radially stabilized via a proximal radial
bearing 116 and a distal radial bearing 118.
[0272] Typically, coupling portion 31 of frame 34 is coupled to
proximal radial bearing 116, for example, via snap-fit coupling,
and/or via welding. Typically, at the distal end of frame 34 distal
strut junctions 33 are placed into grooves defined by the outer
surface of distal radial bearing 118, the grooves being shaped to
conform with the shapes of the distal strut portions. The proximal
end of distal-tip element 107 (which defines distal-tip portion
120) typically holds the distal strut portions in their closed
configurations around the outside of distal radial bearing 118, as
shown. For some applications, the device includes a distal
extension 121 that extends distally from the distal radial bearing.
Typically, the extension is configured to stiffen a region of the
distal-tip element into which the distal end of shaft 92 moves
(e.g., an axial-shaft-receiving tube 126, described hereinbelow, or
a portion thereof).
[0273] As described above, axial shaft 92 is radially stabilized
via proximal radial bearing 116 and distal radial bearing 118. In
turn, the axial shaft, by passing through lumen 62 defined by the
impeller, radially stabilizes the impeller with respect to the
inner surface of frame 34, such that even a relatively small gap
between the outer edge of the blade of the impeller and the inner
surface of frame 34 (e.g., a gap that is as described above) is
maintained, during rotation of the impeller, as described
hereinabove. For some applications, axial shaft 92 is made of
stainless steel, and proximal bearing 116 and/or distal bearing 118
are made of hardened steel. Typically, when crimping (i.e.,
radially constraining) the impeller and the frame for the purpose
of inserting the impeller and the frame into the subject's body,
distal bushing 58 of the impeller is configured to slide along the
axial shaft in the distal direction, such that the impeller becomes
axially elongated, while the proximal bushing remains in an axially
fixed position with respect to the axial shaft. More generally, the
impeller changes from its radially-constrained configuration to its
non-radially-constrained configuration, and vice versa, by the
distal bushing sliding over the axial shaft, while the proximal
bushing remains in an axially fixed position with respect to the
axial shaft. (For some applications, distal bushing 58 of the
impeller is coupled to the shaft via coupling element 65 such that
the axial position of the distal bushing with respect to the shaft
is fixed, and proximal bushing 64 of the impeller is slidable with
respect to the shaft. Such applications are described hereinbelow
with reference to FIGS. 11A-C.)
[0274] Typically, the impeller itself is not directly disposed
within any radial bearings or thrust bearings. Rather, bearings 116
and 118 act as radial bearings with respect to the axial shaft.
Typically, pump portion 27 (and more generally ventricular assist
device 20) does not include any thrust bearing that is configured
to be disposed within the subject's body and that is configured to
oppose thrust generated by the rotation of the impeller. For some
applications, one or more thrust bearings are disposed outside the
subject's body (e.g., within motor unit 23, shown in FIGS. 1A, 7,
and 8A-B), and opposition to thrust generated by the rotation of
the impeller is provided solely by the one or more thrust bearings
disposed outside the subject's body. For some applications, a
mechanical element and/or a magnetic element is configured to
maintain the impeller within a given range of axial positions. For
example, a magnet (e.g., magnet 82, described hereinbelow with
reference to FIG. 7) that is disposed at the proximal end of the
drive cable (e.g., outside the subject's body) may be configured to
impart axial motion to the impeller, and/or to maintain the
impeller within a given range of axial positions.
[0275] Reference is now made to FIGS. 6A and 6B, which are
schematic illustrations of ventricular assist device 20 at
respective stages of a motion cycle of impeller 50 of the
ventricular assist device with respect to frame 34 of the
ventricular assist device, in accordance with some applications of
the present invention. For some applications, while the impeller is
pumping blood through tube 24 by rotating, axial shaft 92 (to which
the impeller is fixated) is driven to move the impeller axially
back-and-forth within frame 34, by the axial shaft moving in an
axial back-and-forth motion, as described in further detail
hereinbelow with reference to FIG. 7. Alternatively or
additionally, the impeller and the axial shaft are configured to
move axially back-and-forth within frame 34 in response to forces
that are acting upon the impeller, and without requiring the axial
shaft to be actively driven to move in the axial back-and-forth
motion. Typically, over the course of the subject's cardiac cycle,
the pressure difference between the left ventricle and the aorta
varies from being approximately zero during ventricular systole
(hereinafter "systole") to a relatively large pressure difference
(e.g., 50-70 mmHg) during ventricular diastole (hereinafter
"diastole"). For some applications, due to the increased pressure
difference that the impeller is pumping against during diastole
(and due to the fact that drive cable 130 is stretchable), the
impeller is pushed distally with respect to frame 34 during
diastole, relative to the location of the impeller with respect to
frame 34 during systole. In turn, since the impeller is connected
to the axial shaft, the axial shaft is moved forward. During
systole, the impeller (and, in turn, the axial shaft) move back to
their systolic positions. In this manner, the axial back-and-forth
motion of the impeller and the axial shaft is generated in a
passive manner, i.e., without requiring active driving of the axial
shaft and the impeller, in order to cause them to undergo this
motion. This passive axial back-and-forth motion of the impeller is
described in further detail hereinbelow, for example, with
reference to FIG. 9. FIG. 6A shows the impeller and axial shaft
disposed at their typical systolic positions and FIG. 6B shows the
impeller and axial shaft disposed at their typical diastolic
positions.
[0276] For some applications, by moving in the axial back-and-forth
motion, the portions of the axial shaft that are in contact with
proximal bearing 116 and distal bearing 118 are constantly
changing. For some such applications, in this manner, the
frictional force that is exerted upon the axial shaft by the
bearings is spread over a larger area of the axial shaft than if
the axial shaft were not to move relative to the bearings, thereby
reducing wear upon the axial shaft, ceteris paribus. Alternatively
or additionally, by moving in the back-and-forth motion with
respect to the bearing, the axial shaft cleans the interface
between the axial shaft and the bearings from any residues, such as
blood residues.
[0277] For some applications, when frame 34 and impeller 50 are in
non-radially-constrained configurations thereof (e.g., when the
frame and the impeller are deployed within the left ventricle), the
length of the frame exceeds the length of the impeller by at least
2 mm (e.g., at least 4 mm, or at least 8 mm). Typically, the
proximal bearing 116 and distal bearing 118 are each 2-4 mm (e.g.,
2-3 mm) in length. Further typically, the impeller and the axial
shaft are configured to move axially within the frame in the
back-and-forth motion at least along the length of each of the
proximal and distal bearings, or at least along twice the length of
each of the bearings. Thus, during the back-and-forth axial
movement of the axial shaft, the axial shaft is wiped clean on
either side of each of the bearings.
[0278] For some applications, the range of the impeller motion is
as indicated in FIGS. 6A-B, with 6A indicating the proximal-most
disposition of the impeller over the course of the cardiac cycle
(at which the impeller is typically disposed during systole) and
FIG. 6B indicating the distal-most disposition of the impeller over
the course of the cardiac cycle (at which the impeller is typically
disposed during diastole). As shown in FIG. 6A, for some
applications, at its proximal-most position the proximal end of the
impeller is disposed at location Ip, which is within the proximal
conical section of frame 34. As shown in FIG. 6B, for some
applications, at its distal-most position the distal end of the
impeller is disposed at location Id, which is at the distal end of
the cylindrical section of frame 34. For the purpose of the present
application, the entire section of the frame from Ip to Id may be
considered as housing the impeller, since this entire section of
the frame typically houses at least a portion of the impeller over
at least a portion of the cardiac cycle. Typically, over the course
of the entire cardiac cycle, the section of the impeller at which
the span of the impeller is at its maximum is disposed within the
cylindrical portion of the frame 34. However, a proximal portion of
the impeller is typically disposed within the proximal conical
section of the frame during at least a portion of the cardiac
cycle.
[0279] Reference is again made to FIGS. 6A and 6B, and reference is
also made to FIG. 6C, which is an enlarged schematic illustration
of distal-tip element 107, which includes axial-shaft-receiving
tube 126 and distal-tip portion 120 of ventricular assist device
20, in accordance with some applications of the present invention.
Typically, distal-tip element 107 is a single integrated element
that includes both axial-shaft-receiving tube 126 and distal-tip
portion 120. For some applications, distal-tip element 107 is
configured to be soft, such that the distal-tip portion is
configured not to injure tissue of the subject, even if the
distal-tip portion comes into contact with the tissue (e.g., tissue
of the left ventricle). For example, distal-tip element 107 may be
made of silicone, polyethylene terephthalate (PET) and/or polyether
block amide (e.g., PEBAX.RTM.). For some applications, the
distal-tip portion defines a lumen 122 therethrough. For some such
applications, during insertion of the ventricular assist device
into the left ventricle, guidewire 10 (FIG. 1B) is first inserted
into the left ventricle, for example, in accordance with known
techniques. The distal-tip portion of the ventricular assist device
is then guided to the left ventricle by advancing the distal-tip
portion over the guidewire, with the guidewire disposed inside
lumen 122. For some applications, a duckbill valve 390 (or a
different type of hemostasis valve) is disposed at the distal end
of lumen 122 of distal-tip portion 120, as described in further
detail hereinbelow.
[0280] Typically, during the insertion of the ventricular assist
device into the subject's ventricle, delivery catheter 143 is
placed over impeller 50 and frame 34 and maintains the impeller and
the frame in their radially-constrained configurations. For some
applications, distal-tip element 107 extends distally from the
delivery catheter during the insertion of the delivery catheter
into the subject's ventricle. For some applications, at the
proximal end of the distal-tip element, the distal-tip element has
a flared portion 124 that acts as a stopper and prevents the
delivery catheter from advancing beyond the flared portion.
[0281] It is noted that the external shape of distal-tip portion in
FIGS. 6A-C (as well as in some other figures) is shown as defining
a complete loop, with the distal end of the distal-tip portion
(within which duckbill valve 390 is disposed) crossing over a more
proximal portion of the distal-tip portion. Typically, as a result
of having had a guidewire inserted therethrough (during insertion
of the ventricular assist device into the left ventricle), the
distal-tip portion remains partially straightened, even after the
removal of the guidewire from the distal-tip portion. Typically,
the partial straightening of the distal-tip portion is such that,
when the distal-tip portion is disposed within the left ventricle,
in the absence of external forces acting upon the distal-tip
portion, the distal-tip portion does not define a complete loop,
e.g., as shown in FIG. 1B, and in FIG. 23A. Other aspects of the
shape of the distal-tip portion are described in further detail
hereinbelow.
[0282] Referring again to FIG. 6C, for some applications,
axial-shaft-receiving tube 126 extends proximally from distal-tip
portion 120 of distal-tip element 107. As described hereinabove,
typically, the axial shaft undergoes axial back-and-forth motion
during the operation of impeller 50. Axial-shaft-receiving tube 126
defines lumen 127, which is configured to receive the axial shaft
when the axial shaft extends beyond distal bearing 118. For some
applications, the shaft-receiving tube defines a stopper 128 at its
distal end, the stopper being configured to prevent advancement of
the axial shaft beyond the stopper. For some applications, the
stopper comprises a rigid component that is inserted (e.g.,
embedded) into the distal end of the shaft-receiving tube.
Alternatively, the stopper comprises a shoulder between lumen 127
of the axial-shaft-receiving tube and lumen 122 of distal-tip
portion 120. Typically, such a shoulder is present since lumen 122
of tip portion 120 is narrower than lumen 127. This is because
lumen 127 is typically configured to accommodate the axial shaft,
while lumen 122 is configured to accommodate guidewire 10, and the
axial shaft is typically wider than guidewire 10, since the axial
shaft is itself configured to accommodate guidewire 10 within
internal lumen 132 (shown in FIGS. 10B and 10C) of the axial
shaft.
[0283] Typically, during normal operation of the impeller, the
axial shaft does not extend to stopper 128, even when drive cable
130 (shown in FIG. 7) is maximally elongated (e.g., during
diastole). However, stopper 128 is configured to prevent the axial
shaft from protruding into the tip portion when the delivery
catheter is advanced over impeller 50 and frame 34, during
retraction of ventricular assist device 20 from the subject's
ventricle. In some cases, during the advancement of the delivery
catheter over the frame and the impeller, the drive cable is at
risk of snapping. In the absence of stopper 128, in such cases the
axial shaft may protrude into the tip portion. Stopper 128 prevents
this from happening, even in the event that the drive cable
snaps.
[0284] Typically, during operation of the ventricular assist
device, and throughout the axial back-and-forth motion cycle of the
impeller, the impeller is disposed in relatively close proximity to
the distal-tip portion. For example, the distance of the impeller
to the distal-tip portion may be within the distal-most 50 percent,
e.g., the distal-most 30 percent (or the distal-most 20 percent) of
tube 24, throughout the back-and-forth motion axial cycle of the
impeller.
[0285] Reference is now made to FIG. 6D, which is a schematic
illustration of impeller 50 and axial shaft 92 of ventricular
assist device 20, a region of the axial shaft being coated with a
coating or a covering material 95, in accordance with some
applications of the present invention. As described hereinabove,
typically, distal bushing 58 of the impeller is not fixedly coupled
to the shaft. Also as described hereinabove, in order to reduce
hemolysis, it is typically desirable to maintain a constant gap
between the edges of the impeller blades and tube 24 (and/or inner
lining 39). Therefore, it is typically desirable to reduce
vibration of the impeller. For some applications, the impeller is
stabilized with respect to the frame by a region along the axial
shaft over which the distal bushing is configured to be slidable
with respect to the axial shaft being coated such as to
substantially prevent the impeller from vibrating, by reducing a
gap (e.g., by substantially filling the gap) between the at least
one bushing and the impeller. For example, the region of the axial
shaft may be coated in polytetrafluoroethylene (e.g., Teflon.RTM.)
and/or diamond-like-carbon (DLC) coating or may be covered with a
sleeve (which is typically a polymer, such as polyester). By
substantially filling the gap between the between the inner surface
of distal bushing 58 and the outer surface of axial shaft 92,
vibration of the impeller is typically reduced relative to if the
region of the axial shaft were not coated. For some applications,
the gap between the distal bushing and the axial shaft is less than
40 micrometers, e.g., less than 30 micrometers, whether or not the
axial shaft is coated. For some applications, the proximal bushing
of the impeller is configured to be slidable with respect to the
axial shaft (for example, as described with reference to FIGS.
11A-C), and similar techniques to those described above are applied
to the proximal bushing.
[0286] Reference is now made to FIG. 6E, which is a schematic
illustration of impeller 50 and axial shaft 92 of ventricular
assist device 20, distal bushing 58 of the impeller including a
protrusion 96 from its inner surface that is configured to slide
within a slot 97 defined by an outer surface of the axial shaft, in
accordance with some applications of the present invention. As
described hereinabove, typically, distal bushing 58 of the impeller
is not fixedly coupled to the shaft. For some applications,
protrusion 96 and slot 97 are configured to prevent the distal end
of the impeller rotating with respect to the axial shaft, as the
impeller undergoes axial motion with respect to the axial shaft.
Typically, at its proximal end, slot 97 defines a stopper 98. The
stopper is configured to prevent the distal bushing from sliding
proximally beyond the stopper, by preventing axial motion of
protrusion 96 proximally beyond the stopper. Typically, by
preventing the distal bushing from sliding proximally beyond the
stopper, a minimum length of the impeller is maintained. In turn,
this typically prevents the span of the impeller from increasing
beyond a given maximum span, which maintains the gap between the
edges of the impeller blades and tube 24 (and/or inner lining
39).
[0287] In accordance with the above description of FIGS. 6A-E (as
well as the description of additional figures), the scope of the
present invention includes one or more techniques for reducing
hemolysis that is caused by the pumping of blood by the impeller.
Typically, frame 34, which is disposed around the impeller defines
a plurality of cells, and the frame is configured such that, in a
non-radially-constrained configuration of the frame, the frame
comprises generally cylindrical portion 38. Further typically, a
cell width CW of each of the cells within the cylindrical portion
as measured around a circumference of the cylindrical portion being
less than 2 mm (e.g., 1.4-1.6 mm, or 1.6-1.8 mm). For some
applications, inner lining 39 lines at least the cylindrical
portion of the frame, and the impeller is disposed inside the frame
such that, in a non-radially-constrained configuration of the
impeller, at a location at which a span of the impeller is at its
maximum, the impeller is disposed within the cylindrical portion of
the frame, such that gap G between an outer edge of the impeller
and the inner lining is less than 1 mm (e.g., less than 0.4 mm).
Typically, the impeller is configured to rotate such as to pump
blood from the left ventricle to the aorta, and to be stabilized
with respect to the frame, such that, during rotation of the
impeller, the gap between the outer edge of the impeller and the
inner lining is maintained and is substantially constant.
Typically, the impeller is configured to reduce a risk of hemolysis
by being stabilized with respect to the frame (such that, during
rotation of the impeller, the gap between the outer edge of the
impeller and the inner lining is maintained and is substantially
constant), relative to if the impeller were not stabilized with
respect to the frame.
[0288] For some applications, proximal and distal radial bearings
116 and 118 are disposed, respectively, at proximal and distal ends
of the frame, and axial shaft 92 passes through the proximal and
distal radial bearings. Typically, the impeller is stabilized with
respect to the frame by the impeller being held in a radially-fixed
position with respect to the axial shaft and the axial shaft being
rigid. For some applications, a gap between each of the axial
bearings and the axial shaft is less than 15 micrometers, e.g.,
between 2 micrometers and 13 micrometers. For some applications,
the impeller includes bushings 64, 58 that are disposed around the
axial shaft, and at least one of the bushings (e.g., distal bushing
58) is configured to be slidable with respect to the axial shaft.
For some applications, the impeller is stabilized with respect to
the frame by a region along the axial shaft over which the at least
one bushing is configured to be slidable with respect to the axial
shaft being coated such as to substantially prevent the impeller
from vibrating, by reducing a gap between the at least one bushing
and the impeller. For example, the region may be coated in a
diamond-like-carbon coating, a polytetrafluoroethylene coating,
and/or a polymeric sleeve. For some applications, the gap between
the distal bushing and the axial shaft is less than 40 micrometers,
e.g., less than 30 micrometers, whether or not the axial shaft is
coated.
[0289] Reference is now made to FIGS. 6F and 6G, which are
schematic illustrations of ventricular assist device 20,
cylindrical portion 38 of frame 34 tapering from a proximal end of
the cylindrical portion to a distal end of the cylindrical portion,
in accordance with some applications of the present invention. As
described hereinabove, for some applications, impeller 50 and axial
shaft 92 are configured to move axially back-and-forth within frame
34 in response to forces that are acting upon the impeller, and
without requiring the axial shaft to be actively driven to move in
the axial back-and-forth motion. Typically, over the course of the
subject's cardiac cycle, the pressure difference between the left
ventricle and the aorta varies from being approximately zero during
systole to a relatively large pressure difference (e.g., 50-70
mmHg) during diastole. For some applications, due to the increased
pressure difference that the impeller is pumping against during
diastole (and due to drive cable 130 being stretchable), the
impeller is pushed distally with respect to frame 34 during
diastole, relative to the location of the impeller with respect to
frame 34 during systole. In turn, since the impeller is connected
to the axial shaft, the axial shaft is moved forward. During
systole, the impeller (and, in turn, the axial shaft) move back to
their systolic positions. In this manner, the axial back-and-forth
motion of the impeller and the axial shaft is generated in a
passive manner, i.e., without requiring active driving of the axial
shaft and the impeller, in order to cause them to undergo this
motion. FIG. 6F shows the impeller disposed at its typical systolic
position and FIG. 6G shows the impeller disposed at its typical
diastolic position.
[0290] For some applications, by virtue of the cylindrical portion
of frame 34 being tapered from the proximal end to the distal end
of the cylindrical portion, the gap between the edges of the
impeller blades and tube 24 (and/or inner lining 39) is less during
diastole than during systole. Due to the smaller gap between the
edges of the impeller blades and tube 24 (and/or inner lining 39),
the pumping efficiency of the impeller is typically greater during
diastole than during systole. For some applications, it is
desirable for the pumping efficiency to be greater during diastole
than during systole, since the impeller is pumping against an
increased pressure gradient during diastole versus during systole,
as described above.
[0291] Notwithstanding the description of the FIGS. 6E and 6F, it
is typically the case that throughout the axial motion cycle of the
impeller the gap between the edges of the impeller blades and tube
24 (and/or inner lining 39) is constant.
[0292] Reference is now made to FIG. 7, which is a schematic
illustration of an exploded view of motor unit 23 of ventricular
assist device 20, in accordance with some applications of the
present invention. For some applications, computer processor 25 of
control console 21 (FIG. 1A) that controls the rotation of impeller
50 is also configured to control the back-and-forth motion of the
axial shaft. Typically, both types of motion are generated using
motor unit 23.
[0293] The scope of the present invention includes controlling the
back-and-forth motion at any frequency. For some applications, an
indication of the subject's cardiac cycle is detected (e.g., by
detecting the subject's ECG), and the back-and-forth motion of the
axial shaft is synchronized to the subject's cardiac cycle.
[0294] Typically, motor unit 23 includes a motor 74 that is
configured to impart rotational motion to impeller 50, via drive
cable 130. As described in further detail hereinbelow, typically,
the motor is magnetically coupled to the drive cable. For some
applications, an axial motion driver 76 is configured to drive the
motor to move in an axial back-and-forth motion, as indicated by
double-headed arrow 79. Typically, by virtue of the magnetic
coupling of the motor to the drive cable, the motor imparts the
back-and-forth motion to the drive cable, which it turn imparts
this motion to the impeller. As described hereinabove and
hereinbelow, for some applications, the drive cable, the impeller,
and/or the axial shaft undergo axial back-and-forth motion in a
passive manner, e.g., due to cyclical changes in the pressure
gradient against which the impeller is pumping blood. Typically,
for such applications, motor unit 23 does not include axial motion
driver 76.
[0295] For some applications, the magnetic coupling of the motor to
the drive cable is as shown in FIG. 7. As shown in FIG. 7, a set of
driving magnets 77 are coupled to the motor via a driving magnet
housing 78. For some applications, the driving magnet housing
includes ring 81 (e.g., a steel ring), and the driving magnets are
adhered to an inner surface of the ring. For some applications a
spacer 85 is adhered to the inner surface of ring 81, between the
two driving magnets, as shown. A driven magnet 82 is disposed
between the driving magnets such that there is axial overlap
between the driving magnets and the driven magnet. The driven
magnet is coupled to a pin 131, which extends to beyond the distal
end of driven magnet 82, where the pin is coupled to the proximal
end of drive cable 130. For example, the driven magnet may be
cylindrical and define a hole therethrough, and pin 131 may be
adhered to an inner surface of the driven magnet that defines the
hole. For some applications, the driven magnet is cylindrical, and
the magnet includes a North pole and a South pole, which are
divided from each other along the length of the cylinder along a
line 83 that bisects the cylinder, as shown. For some applications,
the driven magnet is housed inside a cylindrical housing 87.
Typically, pin 131 defines a guidewire lumen 133, which is
described in further detail hereinbelow with reference to FIGS.
10B-C.
[0296] It is noted that in the application shown in FIG. 7, the
driving magnets are disposed outside the driven magnet. However,
the scope of the present application includes reversing the
configurations of the driving magnets and the driven magnet,
mutatis mutandis. For example, the proximal end of the drive cable
may be coupled to two or more driven magnets, which are disposed
around a driving magnet, such that there is axial overlap between
the driven magnets and the driving magnet.
[0297] As described hereinabove, typically purging system 29 (shown
in FIG. 1A) is used with ventricular assist device 20. Typically,
motor unit 23 includes an inlet port 86 and an outlet port 88, for
use with the purging system. For some applications, a purging fluid
is continuously or periodically pumped into the ventricular assist
device via inlet port 86 and out of the ventricular assist device
via outlet port 88. Additional aspects of the purging system are
described hereinbelow.
[0298] Typically, magnet 82 and pin 131 are held in axially fixed
positions within motor unit 23. The proximal end of the drive cable
is typically coupled to pin 131 and is thereby held in an axially
fixed position by the pin. Typically, drive cable 130 extends from
pin 131 to axial shaft 92 and thereby at least partially fixes the
axial position of the axial shaft, and in turn impeller 50. For
some applications, the drive cable is somewhat stretchable. For
example, the drive cable may be made of coiled wires that are
stretchable. The drive cable typically allows the axial shaft (and
in turn the impeller) to assume a range of axial positions (by the
drive cable becoming more or less stretched), but limits the axial
motion of the axial shaft and the impeller to being within a
certain range of motion (by virtue of the proximal end of the drive
cable being held in an axially fixed position, and the
stretchability of the drive cable being limited).
[0299] Reference is now made to FIGS. 8A and 8B, which are
schematic illustrations of motor unit 23, in accordance with some
applications of the present invention. In general, motor unit 23 as
shown in FIGS. 8A and 8B is similar to that shown in FIG. 7, and,
unless described otherwise, motor unit 23 as shown in FIGS. 8A and
8B contains similar components to motor unit 23 as shown in FIG. 7.
For some applications, the motor unit includes a heat sink 90 that
is configured to dissipate heat that is generated by the motor.
Alternatively or additionally, the motor unit includes ventilation
ports 93 that are configured to facilitate the dissipation of heat
that is generated by the motor. For some applications, the motor
unit includes vibration dampeners 94 and 96 that are configured to
dampen vibration of the motor unit that is caused by rotational
motion and/or axial back-and-forth motion of components of the
ventricular assist device.
[0300] As described hereinabove, for some applications, impeller 50
and axial shaft 92 are configured to move axially back-and-forth
within frame 34 in response to forces that act upon the impeller,
and without requiring the axial shaft to be actively driven to move
in the axial back-and-forth motion. Typically, over the course of
the subject's cardiac cycle, the pressure difference between the
left ventricle and the aorta varies from being approximately zero
during systole to a relatively large pressure difference (e.g.,
50-70 mmHg) during diastole. For some applications, due to the
increased pressure difference that the impeller is pumping against
during diastole (and due to the drive cable being stretchable), the
impeller is pushed distally with respect to frame 34 during
diastole, relative to the location of the impeller with respect to
frame 34 during systole. In turn, since the impeller is connected
to the axial shaft, the axial shaft is moved forward. During
systole, the impeller (and, in turn, the axial shaft) move back to
their systolic positions. In this manner, the axial back-and-forth
motion of the impeller and the axial shaft is generated in a
passive manner, i.e., without requiring active driving of the axial
shaft and the impeller, in order to cause them to undergo this
motion.
[0301] Reference is now made to FIG. 9, which is a graph indicating
variations in the length of a drive cable of a ventricular assist
device, as a pressure gradient against which the impeller of the
ventricular assist device varies, as measured in experiments
performed by inventors of the present application. An impeller and
a drive cable as described herein were used to pump a
glycerin-based solution through chambers, with the chambers set up
to replicate the left ventricle and the aorta, and the solution
having properties (such as, density and viscosity) similar to those
of blood. The pressure gradient against which the impeller was
pumping varied, due to an increasing volume of fluid being disposed
within the chamber into which the impeller was pumping. At the same
time, movement of the drive cable was imaged and changes in the
length of the drive cable were determined via machine-vision
analysis of the images. The graph shown in FIG. 9 indicates the
changes in the length of the drive cable that were measured, as a
function of the pressure gradient. The y-axis of the graph shown in
FIG. 9 is such that 0 mm elongation represents the length of the
drive cable when the impeller is at rest. It is noted that the
graph starts at a pressure gradient value of 65 mmHg, and that at
this pressure the elongation is negative (at approximately -0.25
mm), i.e., the drive cable is shortened relative to the length of
the drive cable prior to initiation of rotation of the impeller.
This is because the drive cable was configured such that, when the
impeller first started pumping, the drive cable shortened (relative
to the length of the drive cable before the impeller was
activated), due to coils within the drive cable unwinding. As seen
in the section of the curve that is shown in FIG. 9, after the
initial shortening of the drive cable that resulted from the
aforementioned effect, it was then the case that as the pressure
gradient increased, the drive cable became increasingly
elongated.
[0302] As indicated by the results shown in FIG. 9 and as described
hereinabove, it is typically the case that, in response to
variations in the pressure against which the impeller is pumping
blood (e.g., the pressure difference between the left ventricle and
the aorta), the impeller moves back and forth with respect to frame
34. In turn, the movement of the impeller causes drive cable 130 to
become more or less elongated.
[0303] For some applications, during operation of the ventricular
assist device, computer processor 25 of control console 21 (FIG.
1A) is configured to measure an indication of the pressure exerted
upon the impeller (which is indicative of the pressure difference
between the left ventricle and the aorta), by measuring an
indication of tension in drive cable 130, and/or axial motion of
the drive cable. For some applications, based upon the measured
indication, the computer processor detects events in the subject's
cardiac cycle, determines the subject's left-ventricular pressure,
and/or determines the subject's cardiac afterload. For some
applications, the computer processor controls the rotation of the
impeller, and/or the axial back-and-forth motion of the axial shaft
in response thereto.
[0304] Referring again to FIG. 7, for some applications,
ventricular assist device 20 includes a sensor 84. For example, the
sensor may include a Hall sensor that is disposed within motor unit
23, as shown in FIG. 7. For some applications, the Hall sensor
measures variations in the magnetic field that is generated by one
of the magnets in order to measure the axial motion of drive cable
130, and, in turn, to determine the pressure against which the
impeller is pumping. For example, the inner, driven magnet 82 may
be axially longer than the outer, driving magnets 77. Due to the
inner magnet being longer than the outer magnets, there are
magnetic field lines that emanate from the inner magnet that do not
pass to the outer magnets, and the magnetic flux generated by those
field lines, as measured by the Hall sensor, varies as the drive
cable, and, in turn, the inner magnet moves axially. During
operation, motor 74 rotates, creating an AC signal in the Hall
sensor, which typically has a frequency of between 200 Hz and 800
Hz. Typically, as the tension in the drive cable changes due to the
subject's cardiac cycle, this gives rise to a low frequency
envelope in the signal measured by the Hall sensor, the low
frequency envelope typically having a frequency of 0.5-2 Hz. For
some applications, the computer processor measures the low
frequency envelope, and derives the subject's cardiac cycle from
the measured envelope. It is noted that typically the axial motion
of the magnet is substantially less than that of the impeller,
since the full range of motion of the impeller isn't transmitted
along the length of the drive cable. However, it is typically the
case that the axial back-and-forth motion of the impeller gives
rise to a measurable back-and-forth motion of the magnet.
[0305] For some applications, the Hall sensor measurements are
initially calibrated, such that the change in magnetic flux per
unit change in pressure against which the impeller is pumping
(i.e., per unit change in the pressure difference between the left
ventricle and the aorta) is known. It is known that, in most
subjects, at systole, the left-ventricular pressure is equal to the
aortic pressure. Therefore, for some applications, the subject's
aortic pressure is measured (e.g., using techniques as described
hereinbelow with reference to FIGS. 16A-D), and the subject's
left-ventricular pressure at a given time is then calculated by the
computer processor, based upon (a) the measured aortic pressure,
and (b) the difference between the magnetic flux measured by the
Hall sensor at that time, and the magnetic flux measured by the
Hall sensor during systole (when the pressure in the left ventricle
is assumed to be equal to that of the aorta).
[0306] For some applications, generally similar techniques to those
described in the above paragraph are used, but rather than
utilizing Hall sensor measurements, a different parameter is
measured in order to determine left ventricular blood pressure at a
given time. For example, it is typically the case that there is a
relationship between the amount of power that is required to power
the rotation of the impeller at a given rotation rate and the
pressure difference that is generated by the impeller. (It is noted
that some of the pressure difference that is generated by the
impeller is used to overcome the pressure gradient against which
the impeller is pumping, and some of the pressure difference that
is generated by the impeller is used to actively pump the blood
from the left ventricle to the aorta, by generating a positive
pressure difference between the left ventricle and the aorta.
Moreover, the relationship between the aforementioned components
typically varies over the course of the cardiac cycle.) For some
applications, calibration measurements are performed, such that the
relationship between (a) power consumption by the motor that is
required to rotate the impeller at a given rotation rate and (b)
the pressure difference that is generated by the impeller, is
known. For some applications, the subject's aortic pressure is
measured (e.g., using techniques as described hereinbelow with
reference to FIGS. 16A-D), and the subject's left-ventricular
pressure at a given time is then calculated by the computer
processor, based upon (a) the measured aortic pressure, (b) the
power consumption by the motor that is required to rotate the
impeller at a given rotation rate at that time, and (c) the
predetermined relationship between power consumption by the motor
that is required to rotate the impeller at a given rotation rate
and the pressure difference that is generated by the impeller. For
some applications, the above-described technique is performed while
maintaining the rotation rate of the impeller at a constant rate.
Alternatively or additionally, the rotation rate of the impeller is
varied, and the variation of the rotation rate of the impeller is
accounted for in the above-described calculations.
[0307] Typically, tube 24 has a known cross-sectional area (when
the tube is in an open state due to blood flow through the tube).
For some applications, the flow through tube 24 that is generated
by the impeller is determined based on the determined pressure
difference that is generated by the impeller, and the known
cross-sectional area of the tube. For some applications, such flow
calculations incorporate calibration parameters in order to account
for factors such as flow resistance that are specific to the
ventricular assist device (or type of ventricular assist device)
upon which the calculations are performed. For some applications,
the ventricular pressure-volume loop is derived, based upon the
determined ventricular pressure.
[0308] Reference is now made to FIGS. 10A, 10B, and 10C, which are
schematic illustrations of drive cable 130 of ventricular assist
device 20, in accordance with some applications of the present
invention. Typically, the rotational motion of the impeller (which
is imparted via the axial shaft), as well as the axial
back-and-forth motion of the axial shaft described hereinabove, is
transmitted to the axial shaft via the drive cable, as described
hereinabove. Typically, the drive cable extends from motor unit 23
(which is typically disposed outside the subject's body) to the
proximal end of axial shaft 92 (as shown in FIG. 10C, which shows
the connection between the distal end of the drive cable and the
proximal end of the axial shaft). For some applications, the drive
cable includes a plurality of wires 134 (as shown in FIG. 10B) that
are disposed in a tightly-coiled configuration in order to impart
sufficient strength and flexibility to the drive cable, such that a
portion of the cable is able to be maintained within the aortic
arch (the portion corresponding to arrow 145 in FIG. 10A), while
the cable is rotating and moving in the axial back-and-forth
motion. The drive cable is typically disposed within a first outer
tube 140, which is configured to remain stationary while the drive
cable undergoes rotational and/or axial back-and-forth motion. The
first outer tube is configured to effectively act as a bearing
along the length of the drive cable. Typically, the first outer
tube is made of a polymer (such as, polyether ether ketone) that is
configured to be highly resistant to fatigue even under the
frictional forces that are generated by the relative motion between
the drive cable and the first outer tube. However, since such
polymers are typically relatively rigid, only a thin layer of the
polymer is typically used in the first outer tube. For some
applications, the first outer tube is disposed within a second
outer tube 142, which is made of a material having greater
flexibility than that of the first outer tube (e.g., nylon, and/or
polyether block amide), and the thickness of the second outer tube
is greater than that of the first outer tube.
[0309] Typically, during insertion of the impeller and the cage
into the left ventricle, impeller 50 and frame 34 are maintained in
a radially-constrained configuration by delivery catheter 143. As
described hereinabove, in order for the impeller and the frame to
assume non-radially-constrained configurations, the delivery
catheter is retracted. For some applications, as shown in FIG. 10A,
the delivery catheter remains in the subject's aorta during
operation of the left ventricular device, and outer tube 142 is
disposed inside the delivery catheter. For some applications,
during operation of the left ventricular device, a channel 224 is
defined between delivery catheter 143 and outer tube 142. (It is
noted that the channel as shown in FIG. 10A is not to scale, for
illustrative purposes.) Channel 224 is described in further detail
hereinbelow. In order to retract the left ventricular device from
the subject's body, the delivery catheter is advanced over the
impeller and the frame, such that the impeller and the frame assume
their radially-constrained configurations. The catheter is then
withdrawn from the subject's body.
[0310] Referring to FIG. 10C (which shows a cross-sectional view of
drive cable 130 and axial shaft 92), typically, the axial shaft and
the drive cable define a continuous lumen 132 therethrough. For
some applications, the left ventricular device is guided to the
aorta and to the left ventricle by placing the axial shaft and the
cable over guidewire 10 (described hereinabove), such that the
guidewire is disposed inside lumen 132. Typically, the guidewire is
inserted through duckbill valve 390 (or other hemostasis valve)
disposed at the distal end of distal tip portion of distal-tip
element 107. The guidewire passes through guidewire lumen 122 (of
the distal-tip portion), and then passes into lumen 132 which is
defined by the axial shaft at that point. The guidewire then
continues to pass through lumen 132 all the way until the proximal
end of the drive cable. From the proximal end of the drive cable,
the guidewire passes through guidewire lumen 133 defined by pin
131, which is disposed outside of the subject's body even after
insertion of the distal end of ventricular assist device 20 into
the subject's left ventricle. Typically, when the distal end of the
ventricular assist device is disposed inside the subject's left
ventricle, the guidewire is retracted from the subject's body by
pulling the guidewire out of the proximal end of guidewire lumen
133. Subsequently, the axial position of driven magnet 82 (within
which pin 131 is disposed) is fixed such as to be disposed between
driving magnets 77, as shown in FIG. 7. For example, a portion of
motor unit 23 in which the driven magnet is disposed may be coupled
to a portion of the motor unit in which driving magnets 77 are
disposed using click-lock element 150 (shown in FIG. 13B).
[0311] For some applications, by using lumen 132 of the axial shaft
and the cable in the above-described manner, it is not necessary to
provide an additional guidewire guide to be used during insertion
of left-ventricular assist device 20. For some applications, the
axial shaft and the cable each have outer diameters of more than
0.6 mm (e.g., more than 0.8 mm), and/or less than 1.2 mm (e.g.,
less than 1 mm), e.g., 0.6-1.2 mm, or 0.8-1 mm. For some
applications, the diameter of lumen 132, defined by the shaft and
the cable, is more than 0.3 mm (e.g., more than 0.4 mm), and/or
less than 0.7 mm (e.g., less than 0.6 mm), e.g., 0.3-0.7 mm, or
0.4-0.6 mm. For some applications, drive cable 130 has a total
length of more than 1 m (e.g., more than 1.1 m), and/or less than
1.4 m (e.g., less than 1.3 m), e.g., 1-1.4 m, or 1.1-1.3 m.
Typically, the diameters of guidewire lumen 122 and guidewire lumen
133 are generally similar to that of lumen 132.
[0312] Reference is now made to FIGS. 10D, 10E, and 10F, which are
schematic illustrations of respective steps of a technique for
coupling drive cable 130 to axial shaft 92 using a butt-welding
overtube 160, in accordance with some applications of the present
invention. Typically, butt-welding overtube defines a window 162,
and a helical groove 164. For some applications, axial shaft is
inserted into a first end of butt-welding overtube, such that the
proximal end of axial shaft 92 is visible at a given location
across window 162, e.g., at the halfway point across the width of
the window, as shown in the transition from FIG. 10D to FIG. 10E.
Subsequently, drive cable 130 is inserted into the other end of the
butt-welding overtube, until the distal end of the drive cable is
also disposed at the given location across window 162 (e.g., at the
halfway point across the width of the window), and is typically
touching the proximal end of the axial shaft, as shown in the
transition from FIGS. 10E and 10F.
[0313] It is noted that the insertion of the axial shaft and the
drive cable into butt-welding overtube 160 may be in the reverse
order to that shown. Namely, the drive cable may be inserted first,
followed by the axial shaft. It is further noted that, for
illustrative purposes, drive cable is shown as a tube in FIGS.
10D-F. However, the drive cable typically includes a plurality of
coiled wires, e.g., as shown in FIG. 10B.
[0314] Typically, once both the axial shaft and the drive cable
have been inserted into butt-welding overtube 160, a plurality of
welding rings 166 are welded into the butt-welding overtube.
Typically, one ring is welded at the given location across window
162, e.g., at the halfway point across the width of the window.
Further typically, an additional ring is welded on either side of
window 162, but at a location that is spaced from the ends of the
butt-welding overtube. In this manner, the additional welding rings
weld the butt-welding overtube to the axial shaft and drive cable
without the additional welding rings being welded directly onto the
outer surfaces of the axial shaft and the drive cable. For some
applications, this places less strain on the welding rings relative
to if the additional welding rings were to be welded at ends of the
butt-welding overtube, such that the additional welding rings were
to be welded directly onto the outer surfaces of the axial shaft
and the drive cable. Typically, the welding rings are welded to a
depth that is such that the butt-welding overtube is welded to the
axial shaft and the drive cable, without reducing the diameter of
guidewire lumen 132. As shown, typically, the drive cable is
inserted into the butt-welding overtube, such that the helical
groove is disposed around the drive cable. Typically, the helical
groove provides flexibility to the portion of the butt-welding
overtube that is disposed over drive cable 130.
[0315] For some applications, generally similar techniques to those
described for welding the distal end of drive cable 130 to axial
shaft 92, are used for welding the proximal end of the drive cable
to pin 131 (described hereinabove with reference to FIG. 7),
mutatis mutandis. For some applications, the drive cable comprises
portions having respective characteristics (e.g., respective
numbers of wires in the set of coiled wires that comprise the
portions of the drive cable). For some such applications, generally
similar techniques to those described for welding the distal end of
drive cable 130 to axial shaft 92, are used for welding the
respective portions of the drive cable to each other, mutatis
mutandis.
[0316] For some applications, certain features of butt-welding
overtube 160 and the techniques for use therewith are practiced in
the absence of others of the features. For example, the
butt-welding overtube may include the window, and the welding rings
may be welded in the above-described manner, even in the absence of
the helical groove.
[0317] Reference is now made to FIGS. 11A and 11B, which are
schematic illustrations of impeller 50, the impeller being coupled
to axial shaft 92 at the distal end of the impeller and not being
coupled to the axial shaft at the proximal end of the impeller, in
accordance with some applications of the present invention. As
described hereinabove, typically, axial shaft 92 passes through the
axis of impeller 50, via lumen 62 of the impeller. For some
applications, distal bushing 58 of the impeller is coupled to the
shaft via coupling element 65 such that the axial position of the
distal bushing with respect to the axial shaft is fixed, and
proximal bushing 64 of the impeller is slidable with respect to the
axial shaft. The axial shaft itself is radially stabilized via
proximal radial bearing 116 and distal radial bearing 118. Proximal
and distal ends of frame 34 are rigidly coupled to the proximal and
distal bearings, as described hereinabove. In turn, the axial
shaft, by passing through lumen 62 defined by the impeller,
radially stabilizes the impeller with respect to the inner surface
of frame 34, such that even a relatively small gap between the
outer edge of the blade of the impeller and the inner surface of
frame 34 (e.g., a gap that is as described above) is maintained,
during rotation of the impeller, as described hereinabove. For such
applications, typically, when crimping (i.e., radially
constraining) the impeller and the frame for the purpose of
inserting the impeller and the frame into the subject's body,
proximal bushing 64 of the impeller is configured to slide along
the axial shaft in the distal direction, such that the impeller
becomes axially elongated, while the distal bushing remains in an
axially fixed position with respect to the axial shaft. More
generally, the impeller changes from its radially-constrained
configuration to its non-radially-constrained configuration, and
vice versa, by the proximal bushing sliding over the axial shaft,
while the distal bushing remains in an axially fixed position with
respect to the axial shaft.
[0318] Reference is now made to FIG. 11C, which is a schematic
illustration of first and second coupling portions 170A and 170B
for facilitating the crimping of the impeller of FIGS. 11A-B,
independently of other components of frame 34, in accordance with
some applications of the present invention. First and second
portions 170A and 170B are configured to become engaged with each
other. The first portion is disposed on the impeller, and the
second portion is coupled to frame 34 and/or proximal bearing 116.
Referring again to FIGS. 11A and 11B, for some applications, prior
to crimping frame 34, the impeller is radially constricted, by
engaging portions 170A and 170B with each other and axially
elongating the impeller, such as to radially constrict the
impeller. Subsequently, frame 34 is crimped. Typically, when the
impeller and the frame are disposed in the subject's left
ventricle, the first and second coupling portions are decoupled
from each other, such that the proximal end of impeller is able to
move with respect to frame 34 and proximal bearing 116.
[0319] Reference is now made to FIG. 12A, which is a graph showing
the relationship between the pressure gradient against which the
impeller is pumping and the pitch of the impeller when the impeller
is configured as shown in FIGS. 11A-B. As shown, since the proximal
end of the impeller is slidable, as the pressure gradient against
which the impeller is pumping increases, the pitch of the impeller
decreases, due to the impeller blades being axially compressed by
the pressure against which the impeller is pumping. Reference is
also made to FIG. 12B, which is a graph showing pressure-flow
curves for impellers as described herein having respective pitches.
Curve C1 corresponds to an impeller having a relatively small
pitch, C2 corresponds to an impeller having a medium pitch, and C3
corresponds to an impeller having a relatively large pitch. As
shown, the smaller the pitch of the impeller, the greater the
gradient of the pressure-flow curve, ceteris paribus. Moreover, at
relatively high pressure gradients, an impeller having a smaller
pitch generates greater flow than an impeller having a greater
pitch, whereas at relatively low pressure gradients, an impeller
having a larger pitch generates greater flow than an impeller
having a smaller pitch, ceteris paribus. In accordance with FIGS.
12A-B, for some applications, by virtue of the impeller being
coupled to the axial shaft at its distal end and being slidable
with respect to the axial shaft at its proximal end, as the
pressure gradient against which the impeller pumps increases, the
pitch of the impeller decreases. Thus, at higher pressure gradients
(at which a smaller pitch typically generates greater flow), the
impeller has a smaller pitch, while at lower pressure gradients (at
which a larger pitch typically generates greater flow), the
impeller has a greater pitch.
[0320] With reference to the curves shown in FIG. 12B and with
respect to the impeller as it is typically configured in the
context of the present application (i.e., with the proximal bearing
coupled to the axial shaft and not as shown in FIGS. 11A-B), it is
typically desirable that the impeller has the following
characteristics:
[0321] 1) At a rotation rate of less than 20,000 RPM (e.g., less
than 19,000 RPM), when pumping against a pressure gradient of
100-120 mmHg, the impeller provides positive or at least zero flow.
This is so that, even in the eventuality that there is unusually
high backpressure from the aorta to the left ventricle, there is no
blood flow in this direction.
[0322] 2) At a rotation rate of less than 20,000 RPM (e.g., less
than 19,000 RPM), when pumping against a pressure gradient of more
than 50 mmHg (e.g., more than 60 mmHg), for example, 50-70 mmHg,
the impeller provides flow of more than 3.5 L/min (e.g., more than
4.5 L/min), for example 3.5-5 L/min. Under normal physiological
conditions, the pressure gradient between the left ventricle and
the aorta at diastole is within the aforementioned range, and it is
desirable to provide a flow rate as described even during
diastole.
[0323] As indicated in the curves shown in 12B, in order to provide
the first characteristic an impeller having a smaller pitch
(corresponding to curve C1) is preferable, but in order to provide
the second characteristic an impeller having a larger pitch
(corresponding to curve C3) is preferable. With this background in
mind, the inventors of the present application have found that, in
order to satisfy the first and second characteristics in an optimum
manner, it is typically desirable for the impeller to have a pitch
that is such that, when the impeller is in its
non-radially-constrained configuration, the helical elongate
elements of the impeller (and therefore the impeller blades)
undergo a complete revolution of 360 degrees (or would undergo a
complete revolution if they were long enough) over an axial length
of more than 8 mm (e.g., more than 9 mm), and/or less than 14 mm
(e.g., less than 13 mm), e.g., 8-14 mm, 9-13 mm, or 10-12 mm.
Typically, when the impeller has a pitch that is as described, and
at a rotation rate of less than 20,000 RPM (e.g., less than 19,000
RPM) the impeller provides zero or positive flow at a pressure
gradient of more than 100 mmHg, e.g., more than 110 mmHg, and a
flow of more than 3 L/min (e.g., more than 4.5 L/min), for example
3.5-5 L/min, at a pressure gradient of more than 50 mmHg (e.g.,
more than 60 mmHg), for example, 50-70 mmHg. Typically, the
impeller is configured to provide the aforementioned flow rates by
virtue of the impeller having a maximum diameter of more than 7 mm
(e.g. more than 8 mm), when the impeller is in its
non-radially-constrained configuration.
[0324] For some applications, the pitch of helical elongate
elements 52 of the impeller (and therefore the impeller blade)
varies along the lengths of the helical elongate elements, at least
when the impeller is in a non-radially-constrained configuration.
Typically, for such applications, the pitch increases from the
distal end of the impeller (i.e., the end that is inserted further
into the subject's body, and that is placed upstream with respect
to the direction of antegrade blood flow) to the proximal end of
the impeller (i.e., the end that is placed downstream with respect
to the direction of antegrade blood flow), such that the pitch
increases in the direction of the blood flow. Typically, the blood
flow velocity increases along the impeller, along the direction of
blood flow. Therefore, the pitch is increased along the direction
of the blood flow, such as to further accelerate the blood.
[0325] Reference is now made to FIGS. 13A, 13B, and 13C, which are
schematic illustrations of a procedure for purging drive cable 130
of ventricular assist device 20, in accordance with some
applications of the present invention. For some applications,
proximal to proximal bearing 116, axial shaft 92 and cable 130 are
surrounded by first and second outer tubes 140 and 142, as
described hereinabove. Typically, both the first and second outer
tubes remain stationary, during rotation of the drive cable. For
some applications, purging system 29 (shown in FIG. 1A) controls
the flow of a purging fluid (e.g., a fluid containing glucose or
dextrose) via inlet port 86 and outlet port 88 (shown in FIGS. 7,
8A, 8B, 13B, and 13C). The fluid is configured to remove air from
the space between the drive cable and the outer tube, and/or to
reduce frictional forces between drive cable 130 (which rotates),
and outer tube 140 (which remains stationary, during rotation of
the drive cable), and/or to reduce frictional forces between axial
shaft 92 and proximal bearing 116 and/or distal bearing 118.
[0326] Referring to FIG. 13A, for some applications, the purging
fluid is pumped between the first and second outer tubes, and there
is an opening 146 within the first outer tube in the vicinity of
the proximal bearing. For some applications, the purging fluid
flows between first outer tube 140 and drive cable 130 via opening
146, as indicated by purging-fluid-flow arrow 148 in FIG. 13A. In
this manner, the interface between drive cable 130 (which rotates),
and outer tube 140 (which remains stationary, during rotation of
the drive cable) is purged. For some applications, some of the
purging fluid additionally flows to the interface between the axial
shaft and proximal bearing 116, thereby purging the interface
(and/or reducing frictional forces at the interface), as indicated
by purging-fluid-flow arrows 149 in FIG. 13A. Typically, the flow
of the purging fluid in the direction of arrows 149 also prevents
blood from flowing into the interface between the axial shaft and
the proximal bearing.
[0327] As described hereinabove (with reference to FIG. 10B)
typically the drive cable includes a plurality of coiled wire. For
some applications, purging fluid passes into lumen 132 defined by
the drive cable via gaps in the coiled wires. Once the purging
fluid is disposed within lumen 132 it flows in both proximal and
distal directions, as indicated by arrow 151 of FIG. 13A. The
purging fluid that flows in the distal direction typically flows
out of the distal end of lumen 132 and toward lumen 122 defined by
distal-tip portion, as indicated by arrow 152 of FIG. 13A. At the
end of distal-tip portion, the purging fluid is typically prevented
from flowing out of the distal-tip portion by duckbill valve 390.
Therefore, some of the purging fluid typically flows to the
interface between the axial shaft and distal bearing 118, thereby
purging the interface (and/or reducing frictional forces at the
interface), as indicated by purging-fluid-flow arrows 154 in FIG.
13A. Typically, the flow of the purging fluid in the direction of
arrows 154 also prevents blood from flowing into the interface
between the axial shaft and the distal bearing.
[0328] As described above, once the purging fluid is disposed
within lumen 132 it flows in both proximal and distal directions,
as indicated by arrow 151 of FIG. 13A. Referring now to FIG. 13B,
typically, at the proximal end of ventricular assist device 20, the
purging fluid flows in the direction of arrows 156 out of the
proximal end of lumen 132 and then out of the proximal end of lumen
133 defined by pin 131. For some applications, the purging fluid
then flows in the direction of arrow 157 and around driven magnet,
such as to reduce frictional forces that the driven magnet is
exposed to. For some applications, the purging fluid then flows out
of outlet port 88, in the direction of arrow 158. Typically, the
purging fluid is then disposed of. Alternatively, the purging fluid
is pumped back into the device, via inlet port 86.
[0329] With reference to the above description of the purging
procedure that is typically used with ventricular assist device 20,
it is noted that guidewire lumens 122, 132, and 133 (which were
previously used to facilitate insertion of the device over
guidewire 10, as described hereinabove), are typically used as flow
channels for purging fluid, during use of the ventricular assist
device.
[0330] Referring now to FIG. 13C, for some applications,
ventricular assist device includes an additional purging fluid
inlet port 89, which is typically used to pump purging fluid into
channel 224 between delivery catheter 143 and outer tube 142. For
some applications, the purging fluid is pumped into this channel at
a low enough pressure, that it is still possible to detect aortic
blood pressure via this channel, as described in further detail
hereinbelow. For some applications, rather than continuously
pumping purging fluid into channel 224, fluid is pumped into this
channel periodically in order to flush the channel. For some
applications, port 89 and channel 224 are used for aortic pressure
sensing, as described in further detail hereinbelow.
[0331] Reference is now made to FIG. 13D, which is a schematic
illustration of ventricular assist device 20 that includes an
inflatable portion 153 (e.g., a balloon) on its distal tip, the
inflatable portion being configured to be inflated by a fluid that
is used for purging the drive cable of the device, in accordance
with some applications of the present invention. As described
hereinabove, with reference to FIG. 13A, for some applications,
purging fluid is pumped through lumen 132 defined by drive cable
130 and axial shaft 92, such that at least some fluid flows all the
way to the distal end of the axial shaft. Typically, for such
applications, the purging fluid continues to flow into lumen 122 of
distal-tip portion 120. For some applications, inflatable portion
153 is disposed around the distal-tip portion, and a there is an
opening 155 between lumen 122 and the interior of the inflatable
portion. The inflatable portion is inflated by the purging fluid
entering the interior of the inflatable portion, via opening 155.
For some applications, by controlling the pressure at which the
purging fluid is pumped into ventricular assist device 20, the
inflation of the inflatable portion is controlled.
[0332] It is noted that, in accordance with some applications of
the present invention, the shape of distal-tip element 107 as shown
in FIG. 13D (as well as in FIGS. 16A, 16B, 16E, 17D, 30, and 31,
for example) is generally as described in US 2019/0209758 to Tuval,
which is incorporated herein by reference. The scope of the present
invention includes combining the apparatus and methods described
with respect to any one of the figures with any of the shapes of
the distal-tip element described herein. It is further noted that,
in accordance with some applications of the present invention, the
configuration of frame 34 as shown in FIG. 13D is generally as
described in US 2019/0209758 to Tuval, which is incorporated herein
by reference. The scope of the present invention includes combining
the apparatus and methods described with respect to any one of the
figures with any of the shapes of the distal-tip portion and/or
configurations of frame 34 described herein.
[0333] Referring to FIG. 13E, for some applications, as an
alternative to pumping a purging fluid through the ventricular
assist device throughout the operation of the ventricular assist
device, fluid 147 is initially released into the space between
drive cable 130 (which rotates), and outer tube 140 (which remains
stationary, during rotation of the drive cable), such that the
fluid fills the space between the drive cable and outer tube 140,
as well as lumen 132. The fluid is then kept in place, between the
drive cable and outer tube 140, and within lumen 132, typically,
throughout the operation of the ventricular assist device. The
fluid is configured to remove air from the space between the drive
cable and the outer tube, and/or to reduce frictional forces
between drive cable 130 (which rotates), and outer tube 140 (which
remains stationary, during rotation of the drive cable), and/or to
reduce frictional forces between axial shaft and proximal bearing
116 and/or distal bearing 118. For some applications, the fluid is
additionally configured to fill the space between tube 140 and tube
142, e.g., by passing through holes defined by tube 140. For some
such applications, heat conducting elements are disposed within the
first outer tube and/or the second outer tube, in order to
dissipate heat from regions at which a large amount of heat is
generated by frictional forces.
[0334] For some applications, the fluid has a relatively high
viscosity, e.g. a viscosity of more than 100 mPas (e.g., more than
500 mPa.$), for example, between 100 mPas and 1000 mPas, such that
the fluid remains substantially in place, during operation of the
ventricular assist device. For example, petroleum jelly and/or
ultrasound coupling gel may be used as the fluid. For some
applications, in order to pump the fluid toward the distal end of
the ventricular assist device, the fluid is initially heated, in
order to temporarily decrease its viscosity.
[0335] Reference is now made to FIGS. 14A, 14B, and 14C, which are
schematic illustrations of a stator 250 configured to be disposed
inside tube 24 of ventricular assist device 20, proximal to frame
34 and impeller 50, in accordance with some applications of the
present invention. For some applications, the stator is made of a
frame 252 that is coupled to outer tube 142, and a flexible
material 254 (e.g. polyurethane, polyester, silicone, polyethylene
terephthalate (PET), and/or polyether block amide (PEBAX.RTM.) that
is coupled to the frame. Typically, the stator is shaped to define
a plurality of curved projections 256 (e.g., more than 2, and/or
less than 8 curved projections) that extend radially from outer
tube 142, when device 20 is in a non-radially-constrained
configuration. The curvature of the curved projections is typically
such as to oppose the direction of rotation of the impeller. The
stator is typically configured to reduce rotational flow components
from the blood flow prior to the blood flowing from outlet openings
109 of tube 24. For some applications, the projections of stator
250 are not curved.
[0336] Typically, during the insertion of tube 24 to the left
ventricle, the curved projections of the stator are radially
constrained by delivery catheter 143. Upon being released from the
delivery catheter, the curved projections are configured to
automatically assume their curved configurations.
[0337] Reference is now made to FIGS. 15A, 15B, 15C, 15D, and 15E,
which are schematic illustration of a stator 260 that is defined by
tube 24 of ventricular assist device 20, in accordance with some
applications of the present invention. Typically, stator 260
defined by a portion of tube 24 that is disposed proximally with
respect to frame 34 and impeller 50, and is configured to reduce
rotational flow components from the blood flow prior to the blood
flowing from outlet openings 109 of tube 24. For some applications,
stator 260 is made up of one or more curved ribbons 262 that curve
around outer tube 142 within tube 24, as shown in FIG. 15A.
Alternatively or additionally, stator 260 comprises a portion 266
of tube 24, which is twisted, such that the walls of the tube
itself define folds that are such as to reduce rotational flow
components from the blood flow prior to the blood flowing from
outlet openings 109 of tube 24, as shown in FIG. 15B.
[0338] For some applications, along a portion of tube 24 between
the proximal end of frame 34 and outlet openings 109, the tube is
split into a plurality of compartments 267 by a plurality of curved
ribbons 262, such that the compartments define intertwined helices
along the length of the portion of the tube, as shown in FIG. 15C.
Alternatively, along a portion of tube 24 between the proximal end
of frame 34 and outlet openings 109, the tube is split into a
plurality of compartments 269 by a plurality of ribbons 264 that
are parallel with the longitudinal axis of tube 24, as shown in
FIG. 15D. For some applications, within a portion of tube 24
between the proximal end of frame 34 and outlet openings 109, tube
24 includes a plurality of helical tubes 268 that are configured to
function as stator 260. For some applications, the helical tubes
are twisted around each other, as shown. Typically, each of the
examples of stator 260 shown in FIGS. 15A, 15B, 15C, 15D, and 15E
is configured to reduce rotational flow components from the blood
flow prior to the blood flowing from outlet openings 109 of tube
24.
[0339] Reference is now made to FIGS. 16A and 16B, which are
schematic illustrations of ventricular assist device 20, the
ventricular assist device including one or more ventricular
blood-pressure-measurement tubes 220, in accordance with some
applications of the present invention. As described hereinabove,
typically, the ventricular assist device includes tube 24, which
traverses the subject's aortic valve, such that a proximal end of
the tube is disposed within the subject's aorta and a distal end of
the tube is disposed within the subject's left ventricle.
Typically, a blood pump (which typically includes impeller 50), is
disposed within the subject's left ventricle within tube 24, and is
configured to pump blood through tube 24 from the left ventricle
into the subject's aorta. For some applications, ventricular
blood-pressure-measurement tube 220 is configured to extend to at
least an outer surface 212 of tube 24, such that an opening 214 at
the distal end of the blood-pressure-measurement tube is in direct
fluid communication with the patient's bloodstream outside tube 24.
Typically, opening 214 is configured to be within the subject's
left ventricle proximal to the blood pump (e.g., proximal to
impeller 50). A pressure sensor 216 (illustrated schematically in
FIG. 1A) measures pressure of blood within the ventricular
blood-pressure-measurement tube. Typically, by measuring pressure
of blood within the left ventricular blood-pressure-measurement
tube, the pressure sensor thereby measures the subject's blood
pressure outside tube 24 (i.e., left ventricular blood pressure).
Typically, blood-pressure-measurement tube 210 extends from outside
the subject's body to opening 214 at the distal end of the tube,
and pressure sensor 216 is disposed toward a proximal end of the
tube, e.g., outside the subject's body. For some applications,
computer processor 25 (FIG. 1A), receives an indication of the
measured blood pressure and controls the pumping of blood by the
impeller, in response to the measured blood pressure.
[0340] For some applications, the ventricular assist device
includes two or more such ventricular blood-pressure-measurement
tubes 220, e.g., as shown in FIGS. 16A and 16B. For some
applications, based upon the blood pressure as measured within each
of the left ventricular blood-pressure-measurement tubes, computer
processor 25 determines whether the opening of one of the two or
more ventricular blood-pressure-measurement tubes is occluded. This
may occur, for example, due to the opening coming into contact with
the wall of the interventricular septum, and/or a different
intraventricular portion. Typically, in response to determining
that the opening of one of the two or more ventricular
blood-pressure-measurement tubes is occluded, the computer
processor determines the subject's left-ventricular pressure based
upon the blood pressure measured within a different one of the two
or more ventricular blood-pressure-measurement tubes.
[0341] Referring to FIG. 16A, as described hereinabove, for some
applications, drive cable 130 extends from a motor outside the
subject's body to axial shaft 92 upon which impeller 50 is
disposed. Typically, the drive cable is disposed within outer tube
142. For some applications, the drive cable is disposed within
first outer tube 140 and second outer tube 142, as described
hereinabove. For some applications, aortic blood pressure is
measured using at least one aortic blood-pressure-measurement tube
222 that defines an opening 219 in outer tube 142 at its distal
end. The aortic blood-pressure-measurement tube is configured to
extend from outside the subject's body to an outer surface of outer
tube 142 within the subject's aorta, such that the opening at the
distal end of the aortic blood-pressure-measurement tube is in
direct fluid communication with the subject's aortic bloodstream.
Blood pressure sensor 216 is configured to measure the subject's
aortic blood pressure by measuring blood pressure within the aortic
blood-pressure-measurement tube.
[0342] For some applications, the one or more ventricular
blood-pressure measurement tubes 220 and/or one or more aortic
blood-pressure measurement tubes 222 are disposed within outer tube
142, surrounding the drive cable. For some applications, portions
of the one or more blood-pressure-measurement tubes are defined by
the walls of outer tube 142, as shown in the cross-sections of
FIGS. 16A and 16B. For some applications, within outer tube 142,
the blood pressure measurement tubes have elliptical cross-sections
(as shown). Typically, this increases the cross-sectional areas of
the tubes, relative to if they were to have circular
cross-sections. Typically, within a distal portion of each of the
ventricular blood-pressure measurement tubes 220 (which extends to
opening 214), the tube has a circular cross-section. For some
applications, the diameter of the distal portion of the tube is
more than 0.2 mm, and/or less than 0.5 mm (e.g., 0.2-0.5 mm).
[0343] As shown in FIGS. 16A and 16B, for some applications, outer
tube 142 defines a groove 215 in a portion of the outer surface of
the outer tube that is configured to be disposed within tube 24.
Typically, during insertion of the ventricular assist device into
the subject's body, the portion of ventricular
blood-pressure-measurement tube 220 that extends from within tube
24 to at least an outer surface of tube 24, is configured to be
disposed within the groove, such that the portion of the
ventricular blood-pressure-measurement tube does not protrude from
the outer surface of the outer tube.
[0344] Reference is now made to FIGS. 16C and 16D, which are
schematic illustrations of ventricular assist device 20, the device
having an aortic blood pressure measurement channel 224 within
delivery catheter 143, in accordance with some applications of the
present invention. For some applications, during operation of the
ventricular assist device, channel 224 is defined between delivery
catheter 143 and outer tube 142 that extends from the distal end of
the delivery catheter to the proximal end of the delivery catheter.
For example, FIG. 10A shows a gap between the outside of outer tube
142 and the inside of delivery catheter 143, which can function as
the aforementioned channel. (It is noted that the scale of the
channel as shown in FIG. 10A is not to scale, for illustrative
purposes.) Typically, during operation of the ventricular assist
device, the distal end of the delivery catheter is disposed within
the subject's aorta, and the proximal end of the delivery catheter
is disposed outside the subject's body. Therefore, by sensing
pressure within the channel between delivery catheter 143 and outer
tube 142, blood pressure sensor 216 (which is shown in FIG. 1A and
which is typically disposed outside the subject's body) is able to
detect aortic pressure. For some applications, the pressure sensor
senses aortic pressure via port 89, shown in FIG. 13C. As noted
hereinabove, with reference to FIG. 13C, purging fluid is typically
pumped into the channel between delivery catheter 143 and outer
tube 142. For some applications, the purging fluid is pumped into
this channel at a low enough pressure, that it is still possible to
detect aortic blood pressure via the channel, in the
above-described manner.
[0345] For some applications, a spacing tube 240 is placed between
outer tube 142 and delivery catheter 143 along at least a distal
portion of delivery catheter 143, such as to fill the gap between
the outer tube and the delivery catheter. For some applications,
the spacing tube is configured to prevent debris, emboli, and/or
other matter from flowing out of the distal end of the delivery
catheter from where they could flow into carotid arteries 241. For
some applications, the delivery catheter defines a lateral hole
242, which is exposed to the aortic blood stream. For some such
applications, proximal of hole 242, the spacing tube is not
disposed between the delivery catheter and the outer tube, as shown
in FIG. 16C. Thus, proximal of hole 242, channel 224 is defined
between the delivery catheter and outer tube 142, such that the
subject's aortic blood pressure is detected via channel 224, in the
manner described hereinabove. Alternatively, proximal of hole 242,
the spacing tube is disposed between the delivery catheter and the
outer tube, but the spacing tube defines channel 224 which extends
from the hole to the proximal end of the delivery catheter, as
shown in FIG. 16D. Typically, the subject's aortic blood pressure
is detected via channel 224, in the manner described hereinabove
(e.g., via port 89).
[0346] Reference is now made to FIG. 16E, which is a schematic
illustration of ventricular assist device 20, the device including
one or more blood-pressure-measurement sensors 270 that are
disposed on an outer surface of tube 24, in accordance with some
applications of the present invention. For some applications,
generally similar techniques to those described with reference to
ventricular blood-pressure-measurement tube 220 are performed using
an electrical wire 272 that extends along blood-pump tube 24 (and
that typically extends from outside the subject's body) to the
outer surface of tube 24. Blood-pressure-measurement sensor 270 is
disposed at a tip of the wire in electrical communication with the
subject's bloodstream outside of tube 24. The subject's blood
pressure outside tube 24 (e.g., the subject's ventricular blood
pressure and/or the subject's aortic blood pressure) is measured by
detecting an electrical parameter using the sensor. For some
applications, wire 272 and/or sensor 270 is printed onto the outer
surface of tube 24.
[0347] For some applications, sensor 270 is configured to perform
conductance measurements. For some applications, conductance
sensors are disposed inside tube 24 (rather than on the outer
surface of tube 24), but are configured to sense conductance using
frequency that is substantially not attenuated by tube 24. For some
applications, additional conductance sensors are disposed on the
left-ventricular assist device, for example, on distal-tip element
107. For some such applications, computer processor 25 (FIG. 1A)
applies a current between the most distal electrode, which is
typically configured to be disposed near the apex of the heart, and
the most proximal electrode, which is typically configured to be
disposed above the aortic valve.
[0348] Conductance of that current between each pair of the
electrodes is then measured by the computer processor. For some
applications, the application of the current, and the conductance
measurements, are performed using generally similar techniques to
those described in an article entitled "The Conductance Volume
Catheter Technique for Measurement of Left Ventricular Volume in
Young Piglets," by Cassidy et al. (Pediatric Research, Vol. 31, No.
1, 1992, pp. 85-90). For some applications, the computer processor
is configured to derive the subject's real-time left-ventricular
pressure-volume loop based upon the conductance measurements. For
some applications, the computer processor controls a rate of
rotation of the impeller responsively to the derived
pressure-volume loop.
[0349] For some applications, the subject's ventricular blood
pressure is derived from the conductance measurements. For some
such applications, the subject's aortic blood pressure is measured
(e.g., as described hereinabove). The subject's left ventricular
pressure is derived by measuring conductance measurements over the
course of the subject's cardiac cycle, and determining the
difference between the left ventricular pressure and the aortic
pressure at any given point within the cardiac cycle, based upon
having previously calibrated the conductance measurements with
left-ventricular/aortic pressure gradients. For some applications,
the computer processor is configured to calculate the first
derivative of the left-ventricular pressure measurements.
Typically, such changes are indicative of the rate of change of
pressure within the left ventricle, which itself is an important
clinical parameter. It is noted that the first derivative of the
left-ventricular pressure is typically unaffected by changes in
aortic pressure, since the aortic pressure curve is relatively flat
as the left-ventricular pressure curve undergoes changes that are
of clinical importance.
[0350] Reference is now made to FIGS. 17A, 17B, 17C, and 17D, which
are schematic illustrations of outer tube 142 of ventricular assist
device 20, the outer tube including a pitot tube 225 that is
configured to measure blood flow through tube 24 of the device, in
accordance with some applications of the present invention. The
portion of outer tube 142 shown in FIGS. 17A-D is typically
disposed within tube 24. For some applications, a flow obstacle 226
(which is typically funnel shaped) is configured to create a
stagnation region near a stagnation pressure tap 227. For some
applications, flow straighteners 228 are added to the outer surface
of tube 142, in order remove any swirling component of the flow
(which does not contribute to the axial flow rate), as shown in
FIG. 17A. Alternatively, the stagnation pressure tap is disposed
sufficiently proximally within funnel-shaped flow obstacle 226 that
the flow obstacle itself acts to remove the swirling components of
the flow, prior to the blood reaching the stagnation pressure tap,
as shown in FIG. 17B. For some applications, the stagnation
pressure tap includes a short tube 233 that protrudes from outer
tube 142 within funnel-shaped flow obstacle 226, such that the
opening of short tube 233 faces the direction of axial blood flow
through tube 24, as shown in FIG. 17C. Outer tube 142 additionally
defines opening 219, which functions as a static pressure tap 229.
The pressure within stagnation pressure tap 227 and within static
pressure tap 229 is measured using a pressure sensor, e.g., a
pressure sensors that are disposed outside the subject's body, as
described hereinabove with reference to FIGS. 16A-D.
[0351] In some applications, flow through tube 24 is calculated
based upon the pressure measurements. For example, flow through
tube 24 may be calculated using the following equation:
Q = C A 2 .times. .DELTA. .times. .times. P .rho. ##EQU00001##
[0352] in which:
[0353] Q is the flow through tube 24,
[0354] C is a calibration constant that is empirically determined
and accounts for factors such as impeller velocity and the
geometries of pressure taps 227 and 229,
[0355] A is the cross-sectional area of tube 24 (not including the
area that outer tube 142 occupies),
[0356] .DELTA.P is the difference between the stagnation pressure
(measured via pressure tap 227), and the static pressure (measured
via pressure tap 229)
[0357] .rho. is the fluid density of blood.
[0358] Referring to FIG. 17D, for some applications a region 230 of
tube 24 within which pitot tube 225 is disposed is narrowed with
respect to the rest of the cylindrical portion of tube 24. For some
applications, the narrowing of the region facilitates more accurate
measurements being made using the pitot tube. For some
applications, narrow region 230 of tube 24 is configured to be
placed within the subject's aortic valve. Typically, the narrowing
of the tube at region 230 is configured to facilitate placement of
region 230 at the aortic valve. For some applications, tube 24
includes narrow region 230 even in the absence of pitot tube 225,
in order to facilitate placement of this region of the tube at the
aortic valve, in the above-described manner.
[0359] Reference is now made to FIG. 18, which is a schematic
illustration of ventricular assist device 20, the ventricular
assist device including coronary artery tubes and/or wires 304, in
accordance with some applications of the present invention. For
some applications, one or more tubes and/or wires extend along the
outside or the inside of a proximal portion of tube 24. The tubes
and/or wires are shape set, such that in non-radially-constrained
configurations of the tubes and/or wires, distal ends of the tubes
and/or wires extend radially from the outer surface of tube 24. The
tubes and/or wires are positioned to extend radially from an axial
location along tube 24 such that, when the distal ends of the tubes
and/or wires are positioned at the subject's coronary arteries 306,
pump portion 27 of the device is correctly positioned within the
subject's left ventricle 22. For some applications, a medical
professional who is deploying ventricular assist device 20, ensures
that pump portion 27 of the device is correctly positioned within
the subject's left ventricle 22, by inserting the distal ends of
the tubes and/or wires into the coronary arteries 306. For some
applications, tubes are used in the above-described embodiments,
and the tubes extend proximally to the proximal end of the
ventricular assist device (e.g., via outer tubes 140, 142, and/or
via delivery catheter 143). For some such applications, a procedure
is performed with respect to one or more of the coronary arteries
via the tubes. Alternatively or additionally, contrast agent is
injected via the tubes, in order to facilitate imaging of the
current location of the device. For some applications, generally
similar techniques are performed using ventricular blood-pressure
measurement tubes 220, described hereinabove. For example, contrast
agent may be injected via the blood-pressure measurement tubes, in
order to facilitate imaging of the current location of the
device.
[0360] Reference is now made to FIGS. 19A, 19B, 19C, 19D, 19E, 19F,
19G, and 19H, which are schematic illustrations of ventricular
assist device 20, the device including inner lining 39 that lines
the inside of frame 34 that houses impeller 50, in accordance with
some applications of the present invention. (For illustrative
purposes, inner lining 39 and tube 24 on the side of the device
facing out of the page are shown as transparent in FIGS. 19A-E.)
For some applications, inner lining 39 is disposed inside frame 34,
in order to provide a smooth inner surface through which blood is
pumped by impeller. Typically, by providing a smooth surface, the
covering material reduces hemolysis that is caused by the pumping
of blood by the impeller, relative to if the blood were pumped
between the impeller and struts of frame 34. For some applications,
inner lining includes polyurethane, polyester, and/or silicone.
Alternatively or additionally, the inner lining includes
polyethylene terephthalate (PET) and/or polyether block amide
(PEBAX.RTM.).
[0361] Typically, the inner lining is disposed over at least the
inner surface of the cylindrical portion of frame 34 (the
cylindrical portion being indicated in FIGS. 2A-C, for example).
For some applications, tube 24 also covers the cylindrical portion
38 of frame 34, around the outside of the frame, for example, such
that tube 24 and inner lining 39 overlap over at least 50 percent
of the length of the inner lining, for example, over the entire
length of the cylindrical portion of frame 34, e.g., as shown in
FIG. 19A. For some applications, there is only partial overlap
between tube 24 and inner lining 39, e.g., as shown in FIG. 19B.
For example, tube 24 may overlap with inner lining along less than
50 percent (e.g., along less than 25 percent) of the length of the
inner lining. For some such applications, during insertion of
ventricular assist device 20 into the subject's body, the impeller
is advanced distally within frame 34, such that the impeller is not
disposed within the area of overlap between the tube and the inner
lining, such that there is no longitudinal location at which the
impeller, tube 24, frame 34, and inner lining 39 all overlap with
each other.
[0362] Typically, for applications as shown in FIGS. 19A and 19B,
over the area of overlap between inner lining 39 and tube 24, the
inner lining is shaped to form a smooth surface (e.g., in order to
reduce hemolysis, as described hereinabove), and tube 24 is shaped
to conform with the struts of frame 34 (e.g., as shown in the
cross-section in FIG. 19A). Typically, over the area of overlap
between inner lining 39 and tube 24, the tube and the inner lining
are coupled to each other, e.g., via vacuum, via an adhesive,
and/or using a thermoforming procedure, for example as described
hereinbelow.
[0363] For some applications, inner lining 39 and tube 24 are made
of different materials. For example, the inner lining may be made
of polyurethane, and the tube may be made of polyether block amide
(PEBAX.RTM.). Typically, the material from which the inner lining
is made has a higher thermoforming temperature than that of the
material from which the tube is made. For some applications in
which the inner lining and the tube overlap along at least a
portion of frame 34 (e.g., along the cylindrical portion of frame
34), the tube and the inner lining are bonded to each other and/or
the frame in the following manner. Initially, the inner lining is
placed over a mandrel. The frame is then placed over the inner
lining. Subsequently, tube 24 is placed around the outside of the
frame. For some applications, in order to mold tube 24 to conform
with the struts of frame 34, without causing the inner lining to
deform, the frame is heated to a temperature that is above the
thermoforming temperature of tube 24 but below the thermoforming
temperature of inner lining 39. Typically, the frame is heated from
inside the frame, using the mandrel. Typically, while the frame is
heated to the aforementioned temperature, an outer tube (which is
typically made from silicone) applies pressure to tube 24 that
causes tube 24 to be pushed radially inwardly, in order to cause
the tube to conform with the shapes of the struts of the frame, as
shown in the cross-section of FIG. 19A. For some applications, the
combination of the frame, the inner lining, and the portion of tube
24 disposed around the frame is subsequently shape set to a desired
shape and dimensions using shape setting techniques that are known
in the art.
[0364] In accordance with the above description, the scope of the
present invention includes a method for manufacturing a housing for
an impeller of a blood pump that includes performing the following
steps. An inner lining is placed around a mandrel. A cylindrical
portion of a frame is placed around the inner lining, the
cylindrical portion of the frame including struts that define a
generally cylindrical shape. A distal portion of an elongate tube
is placed around at least a portion of the frame, the tube
including a proximal portion that defines at least one blood outlet
opening. While the distal portion is disposed around at least the
portion of the frame, the inner lining, the frame and the distal
portion of the elongate tube are heated, via the mandrel. While
heating the inner lining, the frame and the distal portion of the
elongate tube, pressure is applied from outside the distal portion
of the elongate tube, such as to cause the distal portion of the
elongate tube to conform with a structure of the struts of the
frame, and such as to cause the inner lining and the distal portion
of the elongate tube to become coupled to the frame. For example,
the pressure may be applied by means of a silicone tube that is
placed outside the distal portion of the elongate tube. For some
applications, the inner lining and the elongate tube include an
inner lining and elongate tube that are made from different
materials from each other, and a thermoforming temperature of a
material from which the inner lining is made is higher than a
thermoforming temperature of a material from which the elongate
tube is made. For some such applications, the inner lining, the
frame and the distal portion of the elongate tube are heated to a
temperature that is above the thermoforming temperature of the
material from which the elongate tube is made and below the
thermoforming temperature of the material from which the inner
lining is made.
[0365] Referring to FIG. 19C, for some applications, tube 24 does
not overlap with inner lining 39, but tabs 322 extend through
struts of frame 34 from tube 24 to inner lining 39, and are used to
sealingly couple the tube to the inner lining (e.g., by being
adhered to the inner lining). Alternatively or additionally (not
shown), tabs 322 extend from the inner lining to tube 24 and are
used to sealingly couple the tube to the inner material (e.g., by
being adhered to the tube).
[0366] As described hereinabove, for some applications, the
combination of the frame, the inner lining, and the portion of tube
24 disposed around the frame is shape set to a desired shape and
dimensions using shape setting techniques that are known in the
art. Referring to FIG. 19D, for some applications, the combination
of the frame, the inner lining, and the portion of tube 24 disposed
around the frame is shape set such that a distal portion 330 of
cylindrical portion 38 of the frame is widened with respect to the
rest of the cylindrical portion of the frame. Typically, the
widening of the frame is such that blood inlet opening 108 (which
is typically defined by the inner lining at the distal end of the
cylindrical portion of the frame) is widened relative the rest of
the cylindrical portion of the frame. Typically, the impeller is
disposed in close proximity to the blood inlet opening throughout
operation (and the axial back-and-forth motion) of the impeller,
with the distal end of the impeller typically being disposed within
15 mm of the blood inlet opening throughout operation of the
impeller. For some applications, having a widened blood inlet
opening in close proximity to the impeller reduces turbulence that
is generated as blood flows into the blood inlet opening. The
reduction of turbulence typically increases blood flow and/or
reduces hemolysis that is generated by the impeller relative to if
the frame were to define a non-widened blood inlet opening.
[0367] Referring to FIG. 19E, for some applications, the
combination of the frame, the inner lining, and the portion of tube
24 disposed around the frame is shape set such that a distal
portion 332 of cylindrical portion 38 of the frame converges from
the distal end of the cylindrical portion of the frame and toward
the impeller (such as to define a portion of the frame that is
narrower than the rest of the cylindrical portion of the frame in
the vicinity of the impeller (e.g., in the vicinity of the distal
end of the impeller)). For some applications, having a portion of
the frame that converges toward the impeller reduces turbulence
that is generated as blood flows from the blood inlet opening
toward the impeller. The reduction of turbulence typically
increases blood flow and/or reduces hemolysis that is generated by
the impeller relative to if the frame were not to define the
converging portion.
[0368] Referring to FIG. 19F, for some applications the combination
of the frame, the inner lining, and the portion of tube 24 disposed
around the frame is shape set such that the features described,
respectively, with reference to FIGS. 19D and 19E are combined.
That is to say that a first distal portion 330 of the cylindrical
portion of the frame is widened with respect to the rest of
cylindrical portion 38 of the frame, and a second portion 332 of
the cylindrical portion of the frame converges toward the
impeller.
[0369] Referring to FIG. 19G, for some applications, tube 24 does
not extend to the distal end of cylindrical portion 38 of frame 34.
For some such applications, along the portion of the frame along
which the tube does extend, the tube is configured to limit the
radial expansion of the frame. Along the distal portion of the
cylindrical portion of the frame (over which the tube does not
extend), the expansion of the frame is not limited by tube 24.
Therefore, the distal portion of the cylindrical portion of the
frame is widened with respect to the portion of the cylindrical
portion of the frame that is proximal thereto (over which tube 24
does extend). For some applications, this results in blood inlet
opening 108 being wider than it would be if tube 24 were to extend
along the full length of the cylindrical portion of the frame. As
described with reference to FIG. 19D, typically, the impeller is
disposed in close proximity to the blood inlet opening throughout
operation (and the axial back-and-forth motion) of the impeller,
with the distal end of the impeller typically being disposed within
15 mm of the blood inlet opening throughout operation of the
impeller. For some applications, having a widened blood inlet
opening in close proximity to the impeller reduces turbulence that
is generated as blood flows into the blood inlet opening. The
reduction of turbulence typically increases blood flow and/or
reduces hemolysis that is generated by the impeller relative to if
the frame were to define a non-widened blood inlet opening.
[0370] Referring to FIG. 19H, for some applications, in order to
facilitate coupling of inner lining 39 to frame 34, an outer
covering material is coupled (e.g., using adhesive, vacuum and/or a
thermoforming procedure) to the inner lining from outside frame 34
at certain discrete coupling regions 326 along the length of the
frame. (It is noted that in FIG. 19, tube 24 and frame 34 are shown
in the absence of other components of the ventricular assist device
(such as the impeller and the axial shaft), for illustrative
purposes.) For some applications, at at least one of these coupling
regions, tube 24 comprises the outer covering material, as shown in
the proximal-most coupling region, to the right of FIG. 19G.
Alternatively or additionally, an additional outer covering
material 328 is placed around frame 34 at one or more of the
coupling regions. For example, the additional coupling material may
be made from similar materials to those used for inner lining 39
and/or tube 24. For some applications, at the coupling regions,
frame 34 has a lower density of struts relative to the density of
struts of the frame (i.e., the ratio of the surface area occupied
by the struts to the areas of open spaces between the struts) at
other locations along the length of the frame. For example, as
shown in FIG. 19G, along cylindrical portion 38 of the frame, at
the coupling regions that frame has straight axial struts 329,
whereas at other regions within the cylindrical portion of the
frame, the frame defines zigzag struts, and there is a ratio of two
zigzag struts to each straight strut. Typically, the reduced
density of struts at the coupling regions allows the outer covering
material to be directly coupled to the inner lining over a greater
surface area, than if the frame did not have the reduced strut
density at the coupling region.
[0371] Reference is now made to FIGS. 20A, 20B, and 20C, which are
schematic illustrations of ventricular assist device 20 that
includes an inflatable portion 331 (e.g., a balloon), the
inflatable portion being in respective states of inflation in each
of FIGS. 20A, 20B and 20C, in accordance with some applications of
the present invention. For some applications (as shown), inflatable
portion 331 is inflated in a generally similar manner to that
described hereinabove with reference to inflatable portion 153
shown in FIG. 13D. Namely, the inflatable portion is inflated by
the purging fluid entering the interior of the inflatable portion,
via opening 155. For some applications, by controlling the pressure
at which the purging fluid is pumped into ventricular assist device
20, the inflation of the inflatable portion is controlled.
Alternatively or additionally, an inflation lumen for inflating the
inflatable portion is configured to pass through outer tube 142,
and to then pass along the outer surface of tube 24, and to the
inflatable portion of the distal-tip portion.
[0372] For some applications, the inflatable portion is configured
to be in respective states of inflation during respective phases of
the deployment of ventricular assist device. For some applications,
distal-tip portion 120 has a radially-converging shape (as shown in
FIGS. 20A-C) and is configured to act as a dilator, during
insertion of ventricular assist device via a puncture in the
subject's body, as described hereinabove. In this manner, the
delivery catheter 143 and components of the ventricular assist
device that are disposed within the delivery catheter can be
inserted into the puncture without requiring pre-dilation of the
puncture, and without requiring a separate introducer device, for
facilitating insertion of the delivery catheter through the
puncture. Typically, during the insertion of the distal-tip portion
through the puncture in the subject's body, inflatable portion 331
is maintained in a deflated state, as shown in FIG. 20A.
[0373] For some applications, subsequent to the distal-tip portion
being inserted via the puncture in the subject's body, the
distal-tip portion is used to guide the delivery catheter along
curved anatomy (e.g., the aortic arch). For some applications,
during this stage of the procedure, the inflatable portion is
partially inflated, such as to prevent the distal-tip portion from
causing trauma to the patient's vasculature. The inflatable portion
is shown in the partially inflated state in FIG. 20B.
[0374] For some applications, upon ventricular assist device 20
being deployed such that the distal-tip portion is within the
subject's left ventricle, inflatable portion 331 is more fully
inflated than in the state of the inflatable portion shown in FIG.
20B (e.g., fully inflated). Typically, when the inflatable portion
is more fully inflated, the inflatable portion separates one or
more blood inlet openings 108 from inner structures of the left
ventricle in three dimensions. In this manner, the inflatable
portion separates one or more blood inlet openings 108 from the
interventricular septum, chordae tendineae, papillary muscles,
and/or the apex of the left ventricle. For some applications, the
inflatable portion is shaped such as to direct blood flow from the
left ventricle into the one or more blood inlet openings.
[0375] Typically, a hemostasis valve (e.g., duckbill valve 390) is
disposed within lumen 122 of distal-tip portion 120. For some
applications, the hemostasis valve prevents blood from flowing into
lumen 122, and/or into lumen 132. Typically, the hemostasis valve,
by preventing purging fluid from flowing out of the distal end of
lumen 122, causes the purging fluid to flow toward the interface
between axial shaft 92 and distal bearing 118, as described
hereinabove.
[0376] Reference is now made to FIG. 21, which is a schematic
illustration of ventricular assist device 20 being placed inside a
subject's left ventricle 22 (a transverse cross-sectional view of
the left ventricle being illustrated), in accordance with some
applications of the present invention. (FIG. 21 shows aortic valve
26 overlaid on the transverse cross-section of the left ventricle
even though the aortic valve lies in a different plane from the
plane of the main cross-sectional view, for illustrative purposes.)
Reference is also made to FIGS. 22A-D, which are schematic
illustrations of distal-tip element 107 of the ventricular assist
device that is at least partially curved such as to define a
curvature that is similar to that of a question mark, in accordance
with some applications of the present invention, and to FIGS. 23A
and 23B, which are schematic illustrations of the ventricular
assist device of FIGS. 22C-D disposed inside a subject's left
ventricle, in accordance with some applications of the present
invention.
[0377] For some applications, the ventricular assist device is
guided by the guidewire over which it is inserted toward apex 342
of the left ventricle. The walls of the left ventricle may be
thought of as being made up of the septal wall 338 (which separates
the left ventricle from the right ventricle 340), the posterior
wall 336 (from which the papillary muscles 341 protrude, and above
which the mitral valve apparatus is disposed), and the free wall
334, each of these three walls occupying approximately one third of
the circumference of the left ventricle (as illustrated by the
dashed lines, which trisect the left ventricle in FIG. 21).
Typically, it is undesirable for the distal-tip element (or any
other portions of the ventricular assist device) to come into
contact with the septal wall, since there is a risk that this can
give rise to arrythmias. Further typically, it is desirable to
maintain a distance between the distal-tip element (and any other
portions of the ventricular assist device) from the posterior wall,
in order not to interfere with the mitral valve apparatus, and in
order to prevent the mitral valve apparatus from interfering with
the functioning of the ventricular assist device. Therefore, the
ventricular assist device is typically guided toward the apex, in
such a manner that, if and when the distal-tip element contacts the
inner wall of the left ventricle, it contacts free wall 334, as
shown in FIGS. 21 and 23A-B.
[0378] Typically, the ventricular assist device is introduced into
the subject's ventricle over a guidewire, as described hereinabove.
Distal-tip portion 120 defines guidewire lumen 122, such that the
distal-tip portion is held in a straightened configuration during
the introduction of the ventricular assist device into the
subject's ventricle. For some applications, upon the guidewire
being removed, distal-tip portion is configured to assume its
curved shape. It is noted that FIGS. 22A-D illustrate the shape of
distal-tip portion 120 as it is initially formed. Typically, as a
result of having the guidewire inserted through guidewire lumen 122
(thereby temporarily straightening the distal-tip portion), upon
being deployed within the subject's left ventricle, the curvature
of the distal-tip portion is less than that shown in at least some
of FIGS. 22A-D. For example, FIGS. 22C-D show that the curvature of
the distal-tip portion is such that the curved portion of the
distal-tip portion forms a complete loop. However, the distal-tip
portion of FIGS. 22C-D is shown in FIG. 23A within the subject's
left ventricle and it does not form a complete loop.
[0379] As described hereinabove, distal-tip portion 120 typically
forms a portion of distal-tip element 107 which also includes
axial-shaft receiving tube 126. Typically, distal-tip element 107
is configured such that in its non-constrained configuration (i.e.,
in the absence of any forces acting upon the distal-tip portion),
the distal-tip element is at least partially curved. For some
applications, within a given plane, distal-tip element 107 has a
proximal, straight portion 346 (at least a portion of which
typically comprises axial-shaft-receiving tube 126). The proximal
straight portion of distal-tip element 107 defines a longitudinal
axis 348. The curved portion of distal-tip element 107 curves away
from longitudinal axis 348 in a first direction, and then passes
through an inflection point and curves in the opposite direction
with respect to longitudinal axis 348. For example, as shown in
FIGS. 22A-B, within the plane of the page, the distal-tip element
first curves to the top of the page, then curves to the bottom of
the page, and as shown in FIGS. 22C-D, within the plane of the
page, the distal-tip element first curves to the bottom of the
page, then curves to the top of the page. Typically, when shaped as
shown in FIGS. 22A-D, the distal-tip element defines an overall
curvature that is similar to that of a question mark or a
tennis-racket, the distal-tip element defining a bulge 351 on one
side of the longitudinal axis of the straight proximal straight
portion of the distal-tip element. For some applications, the bulge
is generally shaped as a semi-ellipse. (It is noted that in this
context the term "semi-ellipse" includes a semi-circle. It is
further noted that is some cases, the tip does not define a precise
semi-ellipse, but rather a bulged shape that is substantially
similar to a semi-ellipse.)
[0380] As shown in FIGS. 22A-B, for some applications, after
passing through the inflection point the distal-tip element
continues to curve such that the distal-tip element crosses back
over longitudinal axis 348. FIG. 22A shows an example in which the
end of the distal-tip element does not cross back over the
longitudinal axis yet again, and there is a larger gap between the
distal end of the distal-tip element and the proximal end of the
curved portion. FIG. 22B shows an example in which the end
distal-tip element does cross back over the longitudinal axis yet
again, and there is a smaller gap between the distal end of the
distal-tip element and the proximal end of the curved portion. As
shown in FIGS. 22C-D (which are, respectively, cross-sectional and
isometric views of the same shaped distal-tip element), for some
applications, after passing through the inflection point the tip
does not curve such that the distal-tip element crosses back over
longitudinal axis 348. Rather, all of the curvature of the curved
portion of the distal-tip element occurs on one side of
longitudinal axis 348.
[0381] Referring to FIGS. 22A and 22C, typically, a hemostasis
valve (e.g., duckbill valve 390) is disposed within a distal
section of distal-tip portion 120, and is configured to prevent
blood flow into lumen 122. For some applications, the duckbill
valve 390 is as described in further detail hereinbelow with
reference to FIGS. 28A-C. For example, FIG. 22A shows an example in
which the duckbill valve of FIGS. 28A-C is used. Alternatively, a
different duckbill valve is used, e.g., as shown in FIG. 22C.
Typically, the duckbill valve has a maximum width of less than 3
mm, e.g., less than 2 mm. Typically, the entire duckbill valve is
disposed within a distal section of the distal-tip portion that is
disposed within the distal-most 10 mm, e.g., the distal most 5 mm
of the distal-tip portion. For some applications, the duckbill
valve is proximally facing (i.e., such that the wide inlet of the
valve faces the distal end of distal-tip portion and such that the
narrow tip of the valve faces away from the distal end of
distal-tip portion 120), as described in further detail hereinbelow
with reference to FIGS. 28A-E. For some applications, a guidewire
guide 392 is disposed within distal-tip portion 120 at a location
that is proximal to the duckbill valve (e.g., as shown in FIG.
22A). As shown in FIGS. 22A-D, typically, the distal section of the
distal portion is widened in order to accommodate the duckbill
valve and/or the guidewire guide. For some applications, by virtue
of the distal portion being widened, the distal tip of the
distal-tip portion (via which a guidewire is inserted into the
distal-tip portion) does not have a sharp edge. Rather the edge has
a width of more than 1 mm. Typically, the lack of a sharp edge at
the distal tip of the distal-tip portion helps to prevent the
distal tip of the distal-tip portion from causing trauma to
structure within the left ventricle.
[0382] Typically, upon being deployed within the subject's left
ventricle, the curvature of the curved portion of distal-tip
element 107 is configured to provide an atraumatic tip to
ventricular assist device 20. Further typically, the distal-tip
element is configured to space the inlet openings 108 of the
ventricular assist device from walls of the left ventricle.
[0383] Referring now to FIGS. 23A and 23B, it is first noted that
these figures show a cross-sectional view of the left ventricle 22
in which septal wall 338 is disposed on the left of the page and
free wall 334 is disposed on the right of the page. In this view,
the left atrium 359, and left atrial appendage 358 are visible
above the left ventricle, and right ventricle 340 is visible to the
left of the left ventricle. For some applications, distal-tip
element 107 is configured to separate the blood inlet opening from
a posterior wall of the subject's left ventricle when the
distal-tip element is placed against the apex of the subject's left
ventricle. Typically, the distal-tip element is configured to
separate the blood inlet opening from a septal wall of the
subject's left ventricle as the distal-tip element contacts the
apex of the subject's left ventricle.
[0384] Typically, distal-tip element 107 is inserted into the left
ventricle, such that bulge 351 bulges toward the septal wall 338.
When disposed in this configuration, in response to distal-tip
element 107 being pushed against the apex (e.g., due to a physician
advancing the device or in response to movement of the left
ventricle), the blood inlet opening typically gets pushed in the
direction of free wall 334 and away from the septal wall 338 (in
the direction of the arrows shown in FIG. 23B. Typically, this is
due to proximal straight portion 346 pivoting about the curved
portion of the question mark shape, as shown. By contrast, other
shapes of tips, if disposed in a similar orientation may result in
the blood inlet opening being pushed toward the septal wall. For
example, if the distal-tip element were to have a pigtail tip (in
which the tip curves in a single direction of curvature) that is
oriented such that the pigtail curve is on the free wall side of
the longitudinal axis of the straight portion of the distal-tip
element, then pushing the tip distally would typically cause the
blood inlet openings toward the septal wall due to the loop of the
pigtail curve tightening.
[0385] Reference is now made to FIGS. 24A, 24B, 24C, which are
schematic illustrations of distal-tip element 107, the distal-tip
element being configured to center itself with respect to aortic
valve 26, in accordance with some applications of the present
invention. As shown in FIG. 24A, for some applications, the curved
distal portion is shaped that after curving in the first direction
the curved distal portion defines an elongated straight portion
353, before curving in the second direction. As shown in FIG. 24B,
the distal-tip element is configured such that upon being released
within the subject's aorta, the distal-tip element centers itself
with respect to aortic valve 26. Thus, the distal-tip portion may
be used to guide ventricular assist device through the aortic valve
in an atraumatic manner. This may be desirable, for example, in
instances in which the ventricular assist device is mistakenly
retracted through the aortic valve from the left ventricle, after
the distal-tip element has been released within the left ventricle.
Referring to FIG. 24C, an alternative or additional manner in which
to configure the distal-tip element to provide the above-described
functionality is for the radius of bulge 351 of the distal-tip
element to be sufficiently large such as to center the distal-tip
element with respect to the aortic valve. For example, the radius
of the bulge of the distal-tip element may be greater than 15 mm
(e.g., greater than 17 mm).
[0386] With reference to all of FIGS. 21-24C it is noted that the
scope of the present invention includes using a question-mark or
tennis-racket shaped distal-tip element in combination with any
ventricular assist device, and even in the absence of other
features and/or portions of distal-tip element 107 (such as,
axial-shaft-receiving tube 126).
[0387] Reference is now made to FIG. 25A, which is a schematic
illustration of ventricular assist device 20, tube 24 of the device
being configured to become curved when blood is pumped through the
tube, in accordance with some applications of the present
invention. Reference is also made to FIG. 25B, which is a schematic
illustration of tube 24 of FIG. 25A, in the absence of other
components of the ventricular assist device, in accordance with
some applications of the present invention. Reference is
additionally made to FIG. 25C, which is a schematic illustration of
ventricular assist device 20 of FIGS. 25A-B disposed inside a
subject's aorta 30 and left ventricle 22, in accordance with some
applications of the present invention. It is noted that the view of
the aorta and the left ventricle as shown in FIG. 25C is different
to that shown, for example, in FIG. 1B. FIG. 1B and similar figures
are schematic illustrations, provided for illustrative purposes and
do not necessarily precisely depict the scale and orientation of
the ventricular assist with respect to the anatomy. It is further
noted that the view of the aorta and the left ventricle as shown in
FIG. 25C is different to that shown, for example, in FIGS. 23A and
23B. FIG. 25C shows a cross-sectional view of the left ventricle in
which the posterior wall 336 is disposed on the left of the page
and the free wall 334 is disposed on the right of the page.
[0388] As described hereinabove, for some applications, along a
proximal portion of tube 24, frame 34 is not disposed within the
tube, and the tube is therefore not supported in an open state by
frame 34. Tube 24 is typically made of a blood-impermeable,
collapsible material. For example, tube 24 may include
polyurethane, polyester, and/or silicone. Alternatively or
additionally, the tube is made of polyethylene terephthalate (PET)
and/or polyether block amide (PEBAX.RTM.). Typically, the proximal
portion of the tube is configured to be placed such that it is at
least partially disposed within the subject's ascending aorta. For
some applications, the proximal portion of the tube traverses the
subject's aortic valve, passing from the subject's left ventricle
into the subject's ascending aorta, as shown in FIG. 1B. As
described hereinabove, the tube typically defines one or more blood
inlet openings 108 at the distal end of the tube, via which blood
flows into the tube from the left ventricle, during operation of
the impeller. For some applications, the proximal portion of the
tube defines one or more blood outlet openings 109, via which blood
flows from the tube into the ascending aorta, during operation of
the impeller. During operation of the impeller, the pressure of the
blood flow through the tube typically maintains the proximal
portion of the tube in an open state.
[0389] For some applications, tube 24 is pre-shaped such that,
during operation of the impeller, when the pressure of the blood
flow through the tube maintains the proximal portion of the tube in
an open state, the tube is curved. Typically, the curvature is such
that when the proximal end of the tube is disposed within the
aorta, at least a portion of the tube is disposed within the left
ventricle and curving away from the posterior wall of the left
ventricle, toward the apex of the left ventricle and/or toward the
free wall. Further typically, the curvature is such that when the
proximal end of the tube is disposed within the aorta, at least a
portion of the tube is disposed within the left ventricle and
curving away from the septal wall of the left ventricle, toward the
apex of the left ventricle and/or toward the free wall. For some
applications, the curvature of the tube is such that a separation
is maintained between blood inlet openings 108 and posterior wall
336 of the left ventricle, mitral valve leaflets 402 and/or
subvalvular components of the mitral valve (such as chordae
tendineae 404 and/or papillary muscles 341), as shown in FIG.
25C.
[0390] Typically, tube 24 is pre-shaped using blow molding in a
curved mold, or using a shaping mold after a blow-molding process
or a dipping process. Typically, the distal portion of the tube,
within which frame 34, impeller 50 and axial shaft 92 are disposed,
is maintained in a straight and open configuration by frame 34. The
portion of the tube, which is proximal to frame 34 and which is
disposed within the left ventricle, is typically shaped to define
the above-described curvature. For some applications, the curvature
is such that an angle gamma between the longitudinal axis of the
tube at the proximal end of the tube, and the longitudinal axis of
the tube at the distal end of the tube is greater than 90 degrees
(e.g., greater than 120 degrees, or greater than 140 degrees),
and/or less than 180 degrees (e.g., less than 160 degrees, or less
than 150 degrees), e.g., 90-180 degrees, 90-160 degrees, 120-160
degrees, or 140-150 degrees. For some applications, the curvature
of the tube is such that the surface of the tube that is at the
inside of the curve defines a radius of curvature R that is greater
than 10 mm, e.g. greater than 20 mm, and/or less than 200 mm (e.g.,
100 mm), e.g., 10-200 mm, or 20-100 mm. (A dashed circle with a
dashed line across its diameter is shown in FIG. 25B, in order to
indicate how radius of curvature R is measured.)
[0391] It is noted that tube 24, as described with reference to
FIGS. 25A-C is configured such that (a) in the absence of blood
flowing through the tube, the tube typically collapses in response
to pressure outside the tube exceeding pressure inside the tube,
and (b) when blood flows through the tube at a sufficient rate that
pressure within the tube exceeds pressure outside the tube, then
the tube assumes its pre-shaped, curved configuration. It is
further noted that when tube 24 assumes its curved configuration,
the tube typically causes the portion of drive cable 130 that is
disposed within the curved portion of the tube to also become
curved, as shown in FIGS. 25A and 25C. That is to say that it is
the pre-shaping of the tube itself that typically causes the tube
and the drive cable to curve, rather than the drive cable (or a
different element disposed inside the tube) that causes the tube to
curve. Alternatively, outer tube 140 and/or 142 (which is disposed
around the drive cable) is shaped to define the curve, and the
outer tube causes the drive cable and tube 24 to assume the curved
shapes. For some applications, both outer tube 140 and/or 142 and
tube 24 are shaped to define curved shapes.
[0392] It is noted that tube 24 as shown in FIGS. 25A-C is
generally configured as described hereinabove with reference to
FIG. 2A (i.e., with a conical distal portion 46, and with a
plurality of blood inlet openings 108). However, the scope of the
present invention includes combining the curved configuration of
the tube, as described with reference to FIGS. 25A-C, with other
general configurations of the tube (e.g., as described
hereinabove).
[0393] Reference is now made to FIGS. 25D-E, which are schematic
illustrations of ventricular assist device 20, tube 24 of the
device being configured to become curved when blood is pumped
through the tube, in accordance with some applications of the
present invention. In FIGS. 25D and 25E, tube 24 is shown in the
absence of other components of the ventricular assist device (such
as impeller 50, frame 34, etc.), for illustrative purposes. FIG.
25E is a schematic illustration of ventricular assist device 20 of
FIG. 25D disposed inside a subject's aorta 30 and left ventricle
22, in accordance with some applications of the present invention.
The view of the left ventricle shown in FIG. 25E is similar to that
shown in FIG. 25C. For some applications, inlet openings 108 and/or
outlet openings 109 are disposed in a non-axisymmetric
configuration around tube 24. Typically, tube 24 defines the inlet
openings and/or the outlet openings at locations that are such as
to cause tube 24 to become curved and/or such as to maintain the
curvature of tube 24 as described with reference to FIGS. 25A-C.
For example, as shown, the blood inlet holes may be disposed on the
side of tube 24 that is at the inside of the curve of the tube (or
on the inside of the desired curve of the tube). As blood flows
into the blood inlet opening, this lowers the pressure in the
region above the blood inlet opening, and the distal end of tube 24
is then pulled toward this region (as indicated by arrow 310).
Alternatively or additionally, the blood outlet openings 109 may be
disposed on the side of tube 24 that is at the inside of the curve
of the tube (or on the inside of the desired curve of the tube). As
blood exits the blood outlet openings the blood impacts the wall of
the aorta, which causes the proximal end of tube 24 to be pushed in
the opposite direction, in the direction of arrow 312.
[0394] As described with reference to FIGS. 25A-C, typically, the
curvature of the tube is such that a separation is maintained
between blood inlet openings 108 and posterior wall 336 of the left
ventricle, mitral valve leaflets 402 and/or subvalvular components
of the mitral valve (such as chordae tendineae 404 and/or papillary
muscles 341), as shown in FIG. 25E. Typically, the curvature is
such that when the proximal end of the tube is disposed within the
aorta, at least a portion of the tube is disposed within the left
ventricle and curving away from the posterior wall of the left
ventricle, toward the apex of the left ventricle and/or toward the
free wall. Further typically, the curvature is such that when the
proximal end of the tube is disposed within the aorta, at least a
portion of the tube is disposed within the left ventricle and
curving away from the septal wall of the left ventricle, toward the
apex of the left ventricle and/or toward the free wall.
[0395] Reference is now made to FIG. 25F, which is a schematic
illustration of ventricular assist device 20, the ventricular
assist device including a curved element 410 that is configured to
provide tube 24 with a predefined curvature, in accordance with
some applications of the present invention. For some applications,
as an alternative or in addition to tube 24 itself being shaped to
define a curve (e.g., as described with reference to FIGS. 24A-E),
the ventricular assist device includes curved element 410.
Typically, the curved element is made of a shape-memory material,
e.g., a shape-memory alloy, such as nitinol. For some applications,
the curved element is formed from a nitinol tube that is cut to
define holes or slits, such that the tube is able to be pre-shaped
in the desired curved shape. For example, the nitinol element may
be what is known in the art as a nitinol "hypotube" (i.e., a
nitinol tube with micro-engineered features along its length).
Typically, curved element 410 is disposed around drive cable 130
along a longitudinal section of the drive cable that is proximal to
(e.g., immediately proximal to) proximal radial bearing 116. For
some applications, along this longitudinal section of the drive
cable, the curved element is used in place of outer tube 142.
[0396] For some applications, the curved element is shape set to
have a curvature that is generally similar to that described with
respect to tube 24, with reference to FIGS. 25A-E. For some
applications, the curvature is such that angle omega between the
longitudinal axis of the curved element at the proximal end of the
curved element, and the longitudinal axis of the curved element at
the distal end of the curved element is greater than 90 degrees
(e.g., greater than 120 degrees, or greater than 140 degrees),
and/or less than 180 degrees (e.g., less than 160 degrees, or less
than 150 degrees), e.g., 90-180 degrees, 90-160 degrees, 120-160
degrees, or 140-150 degrees. For some applications, the curvature
of the tube is such that the surface of the curved element that is
at the inside of the curve defines radius of curvature that is
greater than 10 mm, e.g. greater than 20 mm, and/or less than 200
mm (e.g., 100 mm), e.g., 10-200 mm, or 20-100 mm. As described with
reference to FIGS. 25A-C, typically, the curvature of the tube is
such that a separation is maintained between blood inlet openings
108 and posterior wall 336 of the left ventricle, mitral valve
leaflets 402 and/or subvalvular components of the mitral valve
(such as chordae tendineae 404 and/or papillary muscles 341), as
shown in FIG. 25C. Typically, the curvature is such that when the
proximal end of the tube is disposed within the aorta, at least a
portion of the tube is disposed within the left ventricle and
curving away from the posterior wall of the left ventricle, toward
the apex of the left ventricle and/or toward the free wall. Further
typically, the curvature is such that when the proximal end of the
tube is disposed within the aorta, at least a portion of the tube
is disposed within the left ventricle and curving away from the
septal wall of the left ventricle, toward the apex of the left
ventricle and/or toward the free wall.
[0397] With reference to FIGS. 25A-F, it is noted that for some
applications tube 24 adopts a curved shape by virtue of outer tube
142 becoming anchored to the aorta and distal-tip portion 120
becoming anchored to the inner wall of the left ventricle (e.g.,
the free wall in the vicinity of the apex), as described
hereinabove. It is further noted that the curvature of the tube
shown in FIGS. 23A-B is less than that shown in FIGS. 25A-F because
FIGS. 23A-B show a different view of the device. In the view shown
in FIGS. 23A-B, the curvature is typically less pronounced than in
the view shown in FIGS. 25A-F.
[0398] Reference is now made to FIGS. 26A, 26B, 26C, 26D, 26E, and
26F, which are schematic illustrations of distal-tip element 107 of
ventricular assist device 20, the distal-tip element being at least
partially curved, in accordance with respective applications of the
present invention. (Distal-tip element 107 is shown in the absence
of the distal end of frame 34, in FIGS. 26B-F.) Typically, the
ventricular assist device is introduced into the subject's
ventricle over a guidewire, as described hereinabove. Distal-tip
portion 120 defines a guidewire lumen 122, such that the distal-tip
portion is held in a straightened configuration during the
introduction of the ventricular assist device into the subject's
ventricle. For some applications, upon the guidewire being removed
distal-tip portion is configured to assume a shape as shown in one
of FIGS. 26A-F.
[0399] Typically, distal-tip element 107 is configured such that in
its non-constrained configuration (i.e., in the absence of any
forces acting upon the distal-tip portion), the distal-tip element
is at least partially curved. For some applications, the distal-tip
element curves around an angle of more than 90 degrees (e.g., more
than 120 degrees), and less than 180 degrees (e.g., less than 160
degrees), e.g., 90-180 degrees, 120-180 degrees, or 120-160
degrees, e.g., as shown in FIG. 26A.
[0400] For some applications, the distal-tip element defines a
first proximal curved portion 343, and defines a second distal
curved portion 344, as shown in FIG. 26B. For some applications,
the first curve defines an angle theta of more than 130 degrees
(e.g., more than 140 degrees), and/or less than 160 degrees (e.g.,
less than 150 degrees), e.g., 130-160 degrees, or 140-150 degrees.
For some applications, the second curve defines an angle alpha of
more than 110 degrees (e.g., more than 120 degrees), and/or less
than 140 degrees (e.g., less than 130 degrees), e.g., 110-140
degrees, or 120-130 degrees. Typically, the stiffness of curved
portions 343, 344 of the distal-tip element 107 is less than that
of a proximal straight portion 346 of the distal-tip element, which
is disposed proximally to both curved portions. For some
applications, the stiffness of second curved portion 344 is less
than that of first proximal curved portion 343.
[0401] Referring to FIGS. 26C and 26D, for some applications,
within a given plane, distal-tip element has proximal, straight
portion 346 that defines a longitudinal axis 348, curves away from
longitudinal axis 348 in a first direction, and then curves in the
opposite direction with respect to longitudinal axis 348. For
example, as shown in FIG. 26C, within the plane of the page, the
distal-tip element first curves to the left of the page, then
curves to the right of the page, and then curves again to the left
of the page. Or, as shown in FIG. 26D, within the plane of the
page, the distal-tip element first curves to the right of the page
and then curves to the left of the page. (The example shown in FIG.
26D is generally similar to that shown in FIG. 22A, except that the
portion of the tip disposed distally to where the tip intersects
longitudinal axis 348 is shorter in FIG. 26D than in FIG. 22).
[0402] It is noted that when shaped as shown in FIG. 26C,
distal-tip element 107 typically defines a first turning point 347
which is disposed on a first side of a longitudinal axis 348 of
proximal straight portion 346 of distal-tip portion 120 (e.g., the
left side of the longitudinal axis, as shown in FIG. 26C), and a
second turning point 349, which is disposed on the opposite side of
longitudinal axis 348 of proximal straight portion 346 of
distal-tip portion 120 (e.g., the right side of the longitudinal
axis, as shown in FIG. 26C). For some applications, the distal-tip
portion is thereby shaped to defined two bulges on respective sides
of longitudinal axis 348. Typically, the distal bulge 412 is larger
(e.g., wider) than proximal bulge 411, as shown. For some
applications, the bulges are generally shaped as semi-ellipses.
Typically, the distal semi-ellipse defines a larger radius than
that of the proximal semi-ellipse, as shown. (It is noted that in
this context the term "semi-ellipse" includes a semi-circle. It is
further noted that is some cases, the tip does not define two
precise semi-ellipses, but rather bulged shapes that are
substantially similar to semi-ellipses.)
[0403] Typically, when shaped as shown in FIG. 26D, the distal-tip
element defines an overall curvature that is similar to that of a
question mark, the tip portion defining a bulge 351 on one side of
the longitudinal axis of the straight proximal straight portion of
the distal-tip portion. For some applications, the bulge is
generally shaped as a semi-ellipse. (It is noted that in this
context the term "semi-ellipse" includes a semi-circle. It is
further noted that is some cases, the tip does not define a precise
semi-ellipse, but rather a bulged shape that is substantially
similar to a semi-ellipse.)
[0404] Typically, upon being deployed within the subject's left
ventricle, the curvature of portions of distal-tip element 107 is
configured to provide atraumaticity to tip portion 120. Further
typically, the distal-tip portion is configured to space the inlet
openings 108 of the ventricular assist device from walls of the
left ventricle.
[0405] For some applications, by curving in at least three
directions such as to define turning points on respective sides of
longitudinal axis 348 (e.g., as shown in FIG. 26C) and/or by
curving in at least two directions (e.g., as shown in FIG. 26D),
the distal-tip element is configured to absorb forces exerted upon
the distal-tip portion by walls of the left ventricle by a greater
amount than if the distal-tip element were to curve in a single
direction.
[0406] For some applications, distal-tip element 107 defines a
plurality of curves each of which defines a different radius of
curvature, and/or curves is a respective direction e.g., as shown
in FIGS. 26E and 26F.
[0407] As described hereinabove, for some applications, duckbill
valve 390 is disposed within a distal section of distal-tip portion
120. The duckbill valve is shown and described in further detail
hereinbelow with reference to FIGS. 28A-C.
[0408] It is noted that for all of the curved distal-tip elements
that are described herein (e.g., with reference to FIGS. 21-24C and
FIGS. 26A-F), typically, the curvatures of the distal-tip portion
are all within a single plane. With reference to all shapes of
distal-tip portions that are described herein (e.g., with reference
to FIGS. 21-24C) the scope of the present invention includes using
a question-mark or tennis-racket shaped distal-tip portion in
combination with any ventricular assist device, and even in the
absence of other features and/or portions of distal-tip element 107
(such as, axial-shaft-receiving tube 126).
[0409] Reference is now made to FIGS. 27A, 27B, and 27C, which are
schematic illustrations of atraumatic projections 350 that are
configured to extend from the distal end of the distal-tip element
107 of ventricular assist device 20, in accordance with respective
applications of the present invention. (Projection 350 is shown in
the absence of distal-tip element 107, in FIGS. 27A-C.) For some
applications, the atraumatic projection includes a closed ellipse
or a closed circle. Typically, the ventricular assist device is
introduced into the subject's ventricle over a guidewire, as
described hereinabove. Along a proximal portion of atraumatic
projection 350, the atraumatic projection defines a guidewire lumen
352. The closed circle or ellipse of the atraumatic projection
typically defines holes 354 in its sidewalls, and the guidewire
passes through these holes. During insertion of the ventricular
assist device into the subject's ventricle, the circle or ellipse
is typically elongated axially, by a proximal portion of the circle
or the ellipse being held within the delivery catheter. Further
typically, a distal portion of the axially-elongated circle or
ellipse protrude from the distal tip of the delivery catheter, and
acts as an atraumatic tip for the delivery catheter, as the
catheter passes through the subject's vasculature.
[0410] Typically, upon being deployed within the subject's left
ventricle, projection 350 is configured to provide an atraumatic
tip to distal-tip element 107. Further typically, the projection is
configured to space the inlet openings 108 of the ventricular
assist device from walls of the left ventricle.
[0411] FIGS. 27A, 27B, and 27C show respective shapes of projection
350, when the projection is in a non-radially-constrained
configuration. Typically, projection 350 is configured to assume
such shapes when the projection is deployed inside the subject's
left ventricle.
[0412] Reference is now made to FIG. 28A, which is a schematic
illustration of duckbill valve 390 and guidewire guide 392 disposed
at the distal end of distal-tip portion 120 of a ventricular assist
device, in accordance with some applications of the present
invention. Reference is also made to FIGS. 28B and 28C, which are
schematic illustrations of views of, respectively, a proximal,
narrow end 420 of duckbill valve 390 and a distal, wide end 422 of
duckbill valve 390, in accordance with some applications of the
present invention. Reference is additionally made to FIGS. 28D and
28E, which are schematic illustration of a proximal end 424 of
guidewire guide 392, and a distal end 426 of guidewire guide 392,
in accordance with some applications of the present invention.
[0413] It is noted that although duckbill valve 390 and guidewire
guide 392 are shown at the distal end of a given example of
distal-tip element 107, the scope of the present invention includes
combining duckbill valve 390 and guidewire guide 392 with any of
the other examples of a distal-tip element described herein.
Moreover, the scope of the present invention includes using
duckbill valve 390 and guidewire guide 392 within the tip of any
percutaneous device and is not limited to using duckbill valve 390
and guidewire guide 392 within a ventricular assist device.
[0414] As described hereinabove, typically, duckbill valve 390 has
a maximum width of less than 3 mm, e.g., less than 2 mm. Typically,
the entire duckbill valve is disposed within a distal section of
the distal-tip portion that is disposed within the distal-most 10
mm, e.g., the distal most 5 mm of the distal-tip portion. Further
typically, as shown, the duckbill valve is proximally facing (i.e.,
such that the wide inlet of the duckbill valve faces the distal end
of distal-tip portion and such that the narrow tip of the duckbill
valve faces away from the distal end of distal-tip portion 120).
This is because typically the pressure of the fluid that is pumped
into distal-tip portion (e.g., as described hereinabove with
reference to FIGS. 13A-C) is greater than the pressure of the blood
in the left ventricle. The duckbill valve is proximally facing, so
as to prevent the fluid from flowing out of the distal end of the
distal portion, such that the fluid flows back toward distal
bearing 118, as described hereinabove. Typically, blood does not
flow into guidewire lumen 122, since the pressure inside guidewire
lumen 122 is greater than the pressure of the blood in the left
ventricle, outside the lumen.
[0415] Typically, ventricular assist device is advanced to the left
ventricle via a guidewire (e.g., guidewire 10, shown in FIG. 1B).
The guidewire is typically inserted into guidewire lumen 122 of
distal-tip portion 120 via the distal end of the distal-tip
portion. Typically, insertion of the guidewire through the distal
end of the distal-tip portion is relatively straightforward, since
distal, wide end 422 of duckbill valve 390 guides the guidewire
through the duckbill valve.
[0416] For some applications, when ventricular assist device is
disposed inside the subject's body, it is desirable to insert
another guidewire from a proximal end of the ventricular assist
device to the distal end of the distal-tip portion. For example, if
a further procedure is going to be performed with respect to the
subject's left ventricle subsequent to the operation of the left
ventricular device, then rather than retracting ventricular assist
device and having to reinsert a guidewire through a percutaneous
puncture, it may be desirable to utilize the existing percutaneous
puncture and to insert the guidewire via guidewire lumen 122,
before retracting ventricular assist device 20.
[0417] Typically, in order to facilitate insertion of a guidewire
through guidewire lumen 122 from a proximal end of the ventricular
assist device, the ventricular assist device includes guidewire
guide 392. Guidewire guide 392 is configured to facilitate
insertion of the guidewire through narrow proximal end 420 of
duckbill valve 390. Guidewire guide is shaped to define a hole 432
therethrough, which narrows in diameter from proximal end 424 of
the guidewire guide to distal end 426 of the guidewire guide. The
shape of the guidewire guide is configured to guide the tip of the
guidewire toward a slit 434 at the narrow, proximal end of the
duckbill valve. For some applications, the duckbill valve is
additionally shaped to define a converging guide portion 430 at its
proximal end, the converging guide portion converging toward slit
434, such that the guide portion is configured to further guide the
tip of the guidewire toward slit 434.
[0418] The scope of the present invention includes using duckbill
valve 390 and guidewire guide 392 within a guidewire lumen of any
percutaneous device and is not limited to using duckbill valve 390
and guidewire guide 392 within a ventricular assist device.
Typically, duckbill valve 390 and guidewire guide 392 facilitate
insertion of a guidewire via the guidewire lumen from a proximal
end of the device to a distal end of the device.
[0419] Reference is now made to FIG. 29, which is a schematic
illustration of a delivery catheter that includes a sheath 440
configured to facilitate reinsertion of a guidewire through a
percutaneous puncture, in accordance with some applications of the
present invention. Typically the sheath comprises a covering (e.g.,
a polyurethane, polyester, silicone, polyethylene terephthalate
(PET), and/or polyether block amide (PEBAX.RTM.) covering) that is
disposed around at least a portion of the circumference of delivery
catheter 143 along a distal section of the length of the delivery
catheter (e.g., along a length of more than 10 mm, and/or less than
100 mm, e.g. 10-100 mm), as shown. As described with reference to
FIGS. 28A-E, for some applications, when ventricular assist device
is disposed inside the subject's body, it is desirable to insert
another guidewire through the existing percutaneous puncture,
rather than retracting ventricular assist device and then having to
reinsert a guidewire through a percutaneous puncture. For some
applications, ventricular assist device and the delivery catheter
are retracted until the proximal end of sheath 440 has been
retracted from the percutaneous puncture. Subsequently, a guidewire
is inserted through the existing percutaneous puncture, by being
advanced through the sheath 440 (i.e. between the covering and the
outer surface of delivery catheter 143). The ventricular assist
device and delivery catheter may then be removed from the
percutaneous puncture, leaving the guidewire in place. For some
applications, sheath 440 is disposed around a portion of outer tube
142 along a distal section of the length of the outer tube, the
functionality of the sheath being generally as described above.
[0420] The scope of the present invention includes using sheath 440
on any type of percutaneous catheter, so as to facilitate
reinsertion of a guidewire via an existing percutaneous puncture,
and is not limited to being used with delivery catheter 143 of
ventricular assist device 20.
[0421] Reference is now made to FIGS. 30 and 31, which are
schematic illustrations of ventricular assist devices 20 that
include two impellers 50, in accordance with some applications of
the present invention. As shown in FIG. 30, for some applications,
first and second impellers are disposed in parallel with each
other, each of the impellers being driven by a respective drive
cable 130. Typically, a first one of the impellers 50 and its
corresponding frame 34 are disposed distally of a second impeller
one of the impellers 50 and its corresponding frame 34, such that
the impellers and frames are not in overlapping configurations with
one another when they are disposed in radially-constrained
configurations within delivery catheter 143. For some applications,
the proximal impeller pumps blood via a parallel tube 24A that runs
parallel to tube 24, with fluid flow from parallel tube 24A flowing
into tube 24 at a location that is configured to be downstream of
the aortic valve 26 (the location of aortic valve 26 being
illustrated schematically in FIG. 30). Thus, typically only tube 24
(without parallel tube 24A) passes through the aortic valve.
[0422] As shown in FIG. 31, for some applications, first and second
impellers are disposed series with each other, each of the
impellers being driven by a single drive cable 130. Typically, a
first one of the impellers 50 and its corresponding frame 34 are
disposed distally of a second impeller one of the impellers 50 and
its corresponding frame 34, such that the impellers and frames are
not in overlapping configurations with one another when they are
disposed in radially-constrained configurations within delivery
catheter 143. Further typically, the impellers pump blood into
respective blood inlet openings 108 and initially one of the
impeller pumps blood through tube 24, while the second impeller
pumps blood through parallel tube 24A of tube 24. Typically, fluid
flow from parallel tube 24A flows into tube 24 at a location that
is configured to be downstream of the aortic valve (the location of
the aortic valve being illustrated schematically in FIG. 30). Thus,
typically only tube 24 (without parallel tube 24A) passes through
the aortic valve.
[0423] It is noted that, by having one of the impellers pump
through parallel tube 24A while the second one of the impellers
pumps blood via tube 24, it is not that case that the proximal
impeller is pumping blood that has already been pumped by the
distal impeller. It has been found by the inventors that, if a
proximal impeller is used to pump blood that has already been
pumped by a distal impeller, this can result in inefficient pumping
of the blood by the proximal impeller. It is further noted that
doubling the number of impellers will typically double the amount
of hemolysis that is generated by ventricular assist device 20,
ceteris paribus. By contrast, increasing the revolution rate of a
single impeller and/or increasing the length of an impeller can
result is a disproportionate increase in the amount of hemolysis
that is generated by the impeller.
[0424] With regards to all aspects of ventricular assist device 20
described with reference to FIGS. 1A-31, it is noted that, although
FIGS. 1A and 1B show ventricular assist device 20 in the subject's
left ventricle, for some applications, device 20 is placed inside
the subject's right ventricle, such that the device traverses the
subject's pulmonary valve, and techniques described herein are
applied, mutatis mutandis. For some applications, components of
device 20 are applicable to different types of blood pumps. For
example, aspects of the present invention may be applicable to a
pump that is used to pump blood from the vena cava and/or the right
atrium into the right ventricle, from the vena cava and/or the
right atrium into the pulmonary artery, and/or from the renal veins
into the vena cava. Such aspects may include features of tube 24
(e.g., the curvature of the tube), impeller 50, features of pump
portion 27, drive cable 130, apparatus and methods for measuring
blood pressure, etc. Alternatively or additionally, device 20
and/or a portion thereof (e.g., impeller 50, even in the absence of
tube 24) is placed inside a different portion of the subject's
body, in order to assist with the pumping of blood from that
portion. For example, device 20 and/or a portion thereof (e.g.,
impeller 50, even in the absence of tube 24) may be placed in a
blood vessel and may be used to pump blood through the blood
vessel. For some applications, device 20 and/or a portion thereof
(e.g., impeller 50, even in the absence of tube 24) is configured
to be placed within the subclavian vein or jugular vein, at
junctions of the vein with a lymph duct, and is used to increase
flow of lymphatic fluid from the lymph duct into the vein, mutatis
mutandis. Since the scope of the present invention includes using
the apparatus and methods described herein in anatomical locations
other than the left ventricle and the aorta, the ventricular assist
device and/or portions thereof are sometimes referred to herein (in
the specification and the claims) as a blood pump.
[0425] Some examples of devices that include components of
ventricular assist device 20, but that are used at different
anatomical locations are described hereinbelow with reference to
FIGS. 32A-33.
[0426] Reference is now made to FIGS. 32A, 32B, 32C, 32D, and 32E,
which are schematic illustration of a cardiac assist device 360
that is configured to assist the functioning of the right heart of
a subject, in accordance with some applications of the present
invention. For components of device 360 that are generally similar
to components described hereinabove with reference to ventricular
assist device 20, the same reference numerals are used as those
used hereinabove. Typically, such components are generally as
described hereinabove, except for the differences that are
described below.
[0427] FIG. 32E shows device 360 in its non-radially-constrained
configuration in the absence of the subject's anatomy. As shown,
typically, to assist the functioning of the subject's right heart,
impeller 50 and frame 34 are disposed at a proximal end of tube 24.
Similarly, blood inlet opening(s) is disposed at the proximal end
of the tube. The impeller is configured to pump blood through tube
24 in the distal direction, toward blood outlet openings 109 that
are disposed at the distal end of tube 24. For some applications, a
balloon 362 is disposed at the distal end of the device. Balloon
362 is configured to facilitate introduction of the distal end of
the device into the pulmonary artery 364, by the balloon migrating
to the pulmonary artery with the subject's blood flow. Typically,
the blood outlet opening(s) is configured to be disposed within the
pulmonary artery, such that the impeller pumps blood via tube 24,
into the pulmonary artery.
[0428] As shown in FIG. 32A, for some applications, the blood inlet
opening(s) 108 is disposed within the subject's right ventricle
366, such that the impeller pumps blood from the right ventricle,
via tube 24, into pulmonary artery 364. Alternatively, the blood
inlet opening(s) 108 is disposed within the subject's right atrium
368, such that the impeller pumps blood from the right atrium, via
tube 24, into pulmonary artery 364, as shown in FIG. 32B. Further
alternatively, the blood inlet opening(s) 108 is disposed within
the subject's superior vena cava 370, such that the impeller pumps
blood from the superior vena cava, via tube 24, into pulmonary
artery 364, as shown in FIG. 32C. Further alternatively, the blood
inlet opening(s) 108 is disposed within the subject's inferior vena
cava 372, such that the impeller pumps blood from the inferior vena
cava, via tube 24, into pulmonary artery 364, as shown in FIG.
32D.
[0429] It is noted that, in the configurations shown in FIGS.
32B-D, the cardiac assist device will lower preload on the right
heart (by pumping blood from the right atrium or the vena cava),
but will increase afterload (by pumping blood into the pulmonary
artery). By contrast, in the configuration shown in FIG. 32A, the
cardiac assist device effectively does not increase afterload,
since the volume of blood that is pumped into the pulmonary artery
by the impeller, is the same volume as is pumped out of the right
ventricle.
[0430] Reference is now made to FIG. 33, which is a schematic
illustration of a venous assist device 380, in accordance with some
applications of the present invention. For components of device 380
that are generally similar to components described hereinabove with
reference to ventricular assist device 20, the same reference
numerals are used as those used hereinabove. Typically, such
components are generally as described hereinabove, except for the
differences that are described below. For some applications, venous
assist device 380 includes impeller 50 and frame 34, which are
generally as described hereinabove. For some applications, the
venous assist device does not include tube 24, for example, as
shown in FIG. 33.
[0431] For some applications, venous assist device 380 is inserted
into a vein of a subject in order to assist with the pumping of
blood through the vein. For example, the venous assist device may
be inserted into a vein 382 of a leg of a subject (such as the
iliac vein or the femoral vein) suffering from an ischemic leg, and
may be used to assist with the pumping of blood through the
vein.
[0432] For some applications, the scope of the present application
includes any one of the following apparatus and methods combined in
combination with any of the other apparatus and methods described
herein:
[0433] A method including: [0434] coupling a rigid tube to a drive
cable that includes a plurality of coiled wires, by:
[0435] placing ends of the drive cable and the rigid tube at a
given location within a butt-welding overtube, the ends of the
drive cable and the rigid tube being visible when they are disposed
at the given location within the butt-welding overtube via a window
defined by the butt-welding overtube, and the placement of the
drive cable within the butt-welding overtube being such that a
helical groove defined by a portion of the butt-welding overtube is
disposed over the drive cable; and forming welding rings around the
butt-welding overtube.
[0436] For some applications, forming welding rings around the
butt-welding overtube includes forming welding rings that are
spaced from edges of the butt-welding overtube, such that the
welding rings weld the butt-welding overtube to the rigid tube and
the drive cable without the welding rings being welded directly
onto outer surfaces of the rigid tube and the drive cable. For some
applications, forming welding rings around the butt-welding
overtube includes forming welding rings to a depth that is such
that that the butt-welding overtube is welded to the rigid tube and
the drive cable, without reducing a diameter of a lumen defined by
the rigid tube and the drive cable. For some applications, forming
welding rings around the butt-welding overtube includes forming at
least one welding ring at the given location within the
butt-welding overtube at which the ends of the drive cable and the
rigid tube are placed. For some applications, coupling the drive
cable to the rigid tube includes coupling the drive cable to an
axial shaft that is configured to support an impeller. For some
applications, coupling the drive cable to the rigid tube includes
coupling the drive cable to a pin that is configured to be coupled
to a magnet, the magnet being configured to be driven to rotate by
a motor. Some examples of such applications are described
hereinabove with reference to FIGS. 10D-E.
[0437] Apparatus including:
[0438] a drive cable including a plurality of coiled wires;
[0439] a rigid tube configured to be coupled to the drive cable;
and
[0440] a butt-welding overtube, the butt-welding overtube
configured to facilitate butt-welding of the drive cable to the
rigid tube, the butt-welding overtube defining: [0441] a window
configured to facilitate placement of ends of the drive cable and
the rigid tube at a given location within the butt-welding
overtube, by providing visibility of the ends of the drive cable
and the rigid tube when they are disposed at the given location
within the butt-welding overtube; and [0442] a helical groove
within a portion of the butt-welding overtube that is configured to
be disposed over the drive cable, and to provide flexibility to the
portion of the butt-welding overtube that is configured to be
disposed over drive cable.
[0443] For some applications, the apparatus includes an impeller,
and the rigid tube includes an axial shaft that is configured to
support the impeller. For some applications, the apparatus includes
a motor and a magnet configured to be driven to rotate by the
motor, and the rigid tube includes a pin that is configured to be
coupled to the magnet. Some examples of such applications are
described hereinabove with reference to FIGS. 10D-E.
[0444] A method including:
[0445] coupling to each other first and second portions of drive
cable that includes a plurality of coiled wires, by: [0446] placing
ends of the first and second portions of the drive cable at a given
location within a butt-welding overtube, [0447] the ends of the
first and second portions of the drive cable being visible when
they are disposed at the given location within the butt-welding
overtube via a window defined by the butt-welding overtube, and
[0448] the placement of at least one of the portions of the drive
cable within the butt-welding overtube being such that a helical
groove defined by a portion of the butt-welding overtube is
disposed over the at least one of the portions of the drive cable;
and [0449] forming welding rings around the butt-welding
overtube.
[0450] Some examples of such applications are described hereinabove
with reference to FIGS. 10D-E.
[0451] A method including:
[0452] coupling a rigid tube to a drive cable that includes a
plurality of coiled wires, by: [0453] placing ends of the drive
cable and the rigid tube at a given location within a butt-welding
overtube, [0454] the ends of the drive cable and the rigid tube
being visible when they are disposed at the given location within
the butt-welding overtube via a window defined by the butt-welding
overtube; and [0455] forming welding rings around the butt-welding
overtube, the welding rings being spaced from edges of the
butt-welding overtube, such that the welding rings weld the
butt-welding overtube to the rigid tube and the drive cable without
being welded directly onto outer surfaces of the rigid tube and the
drive cable.
[0456] For some applications, forming welding rings around the
butt-welding overtube includes forming welding rings to a depth
that is such that that the butt-welding overtube is welded to the
rigid tube and the drive cable, without reducing a diameter of a
lumen defined by the rigid tube and the drive cable. For some
applications, forming welding rings around the butt-welding
overtube includes forming at least one welding ring at the given
location within the butt-welding overtube at which the ends of the
drive cable and the rigid tube are placed. For some applications,
placing ends of the drive cable and the rigid tube at the given
location within the butt-welding overtube includes placing the
drive cable within the butt-welding overtube such that a helical
groove defined by a portion of the butt-welding overtube is
disposed over the drive cable. For some applications, coupling the
drive cable to the rigid tube includes coupling the drive cable to
an axial shaft that is configured to support an impeller. For some
applications, coupling the drive cable to the rigid tube includes
coupling the drive cable to a pin that is configured to be coupled
to a magnet, the magnet being configured to be driven to rotate by
a motor. Some examples of such applications are described
hereinabove with reference to FIGS. 10D-E.
[0457] Apparatus including:
[0458] a blood pump configured to be placed inside a body of
subject, the blood pump including: [0459] an impeller; [0460] a
frame configured to be disposed around the impeller; [0461] an
axial shaft upon which the impeller is disposed; [0462] proximal
and distal radial bearings, configured to stabilize the axial shaft
radially during rotation of the impeller; [0463] an atraumatic
distal-tip portion disposed distally with respect to the impeller,
the atraumatic distal-tip portion including an inflatable portion;
and [0464] a purging fluid configured to be pumped toward the
distal-tip portion, such as to (a) purge the distal bearing, and
(b) inflate the inflatable portion of the distal-tip portion.
[0465] Some examples of such applications are described hereinabove
with reference to FIG. 13D.
[0466] Apparatus including:
[0467] a blood pump configured to be placed inside a body of
subject, the blood pump including: [0468] a tube that defines at
least one blood inlet opening and at least one blood outlet
opening; [0469] an impeller configured to pump blood of the subject
into the blood inlet opening, through the tube, and out of the
blood outlet opening; [0470] a distal-tip portion disposed distally
with respect to the blood inlet opening, the distal-tip portion
defining a radially-converging shape, and being configured to be
placed within a left ventricle of the subject while impeller pumps
the subject's blood; [0471] an inflatable portion disposed around
the distal-tip portion, the inflatable portion being configured to
define: [0472] a) a deflated state, the distal-tip portion being
configured to function as a dilator, during insertion of the blood
pump via a puncture in skin of the subject, when the inflatable
portion is in its deflated state, [0473] b) a first inflation state
in which the inflatable portion is configured to prevent the
distal-tip portion from causing trauma to vasculature of the
subject, during advancement of the distal-tip portion through the
subject's vasculature, and [0474] c) a second inflation state, in
which the inflatable portion is more fully inflated than in the
first inflation state, the inflatable portion when in its second
inflation state being configured to separate the one or more blood
inlet openings from inner structures of the subject's left
ventricle in three dimensions, when the distal-tip portion is
disposed within the subject's left ventricle.
[0475] Some examples of such applications are described hereinabove
with reference to FIGS. 20A-C.
[0476] Apparatus including:
[0477] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including: [0478] a tube configured such that a
proximal portion of the tube traverses an aortic valve of the
subject, and a distal portion of the tube is disposed within a left
ventricle of the subject; [0479] a frame disposed within the distal
portion of the tube, the frame being configured to hold the distal
portion of the tube in an open state, [0480] the frame not being
disposed within the proximal portion of the tube, and the proximal
portion of the tube thereby being configured to collapse inwardly
in response to pressure outside of the proximal portion of the tube
exceeding pressure inside the proximal portion of the tube; [0481]
a pump disposed within the frame and configured to pump blood
through the tube from the subject's left ventricle to the subject's
aorta, such that during pumping of the blood through the tube:
[0482] the proximal portion of the tube is maintained in an open
state, and [0483] at least a portion of the tube becomes curved,
such that the tube curves away from a posterior wall of the left
ventricle.
[0484] For some applications, the pump is configured to pump blood
through the tube from the subject's left ventricle to the subject's
aorta, such that during pumping of the blood through the tube at
least the portion of the tube becomes curved, such that the tube
curves away from a septal wall of the left ventricle. Some examples
of such applications are described hereinabove with reference to
FIGS. 25A-F.
[0485] Apparatus including:
[0486] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including: [0487] a tube configured such that a
proximal portion of the tube traverse an aortic valve of the
subject, and a distal portion of the tube is disposed within a left
ventricle of the subject; [0488] a frame disposed within the distal
portion of the tube, the frame being configured to hold the distal
portion of the tube in an open state, [0489] the frame not being
disposed within the proximal portion of the tube, and the proximal
portion of the tube thereby being configured to collapse inwardly
in response to pressure outside of the proximal portion of the tube
exceeding pressure inside the proximal portion of the tube; [0490]
a pump disposed within the frame and configured to pump blood
through the tube from the subject's left ventricle to the subject's
aorta, such that during pumping of the blood through the tube, the
proximal portion of the tube is maintained in an open state; [0491]
and [0492] a curved element disposed within the tube proximally
with respect to the frame, the curved element being configured to
cause at least a portion of the tube to become curved, such that
the tube curves away from a posterior wall of the left
ventricle.
[0493] For some applications, the curved element is configured to
cause at least the portion of the tube to becomes curved, such that
the tube curves away from a septal wall of the left ventricle. Some
examples of such applications are described hereinabove with
reference to FIGS. 25A-F.
[0494] Apparatus including:
[0495] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including: [0496] a tube configured such that a
proximal portion of the tube traverse an aortic valve of the
subject, and a distal portion of the tube is disposed within a left
ventricle of the subject; [0497] a frame disposed within at least
the distal portion of the tube; [0498] a pump disposed within the
frame and configured to pump blood through the tube from the
subject's left ventricle to the subject's aorta, by pumping the
blood into the tube via a set of one or more blood inlet openings
that are defined by the tube and that are disposed within the
subject's left ventricle, and by pumping blood out of the tube via
a set of one or more blood outlet openings that are defined by the
tube and that are disposed within the subject's aorta; [0499]
wherein at least one of the sets of openings in the tube is
disposed in a non-axi-symmetric configuration with respect to the
tube, such that the pumping of the blood through the at least one
of the sets of openings causes at least a portion of the tube to
become curved, such that the tube curves away from a posterior wall
of the left ventricle.
[0500] For some applications, the at least one of the sets of
openings in the tube is disposed in the non-axi-symmetric
configuration with respect to the tube, such that the pumping of
the blood through the at least one of the sets of openings causes
at least the portion of the tube to become curved, such that the
tube curves away from a septal wall of the left ventricle. Some
examples of such applications are described hereinabove with
reference to FIGS. 25A-F.
[0501] Apparatus including:
[0502] an impeller, including: [0503] an impeller frame that
includes proximal and distal end portions and at least one helical
elongate element that winds from the proximal end portion to the
distal end portion; [0504] a material that is coupled to the at
least one helical elongate element, such that the at least one
helical elongate element with the material coupled thereto defines
a blade of the impeller; and [0505] a coil coiled around the at
least one helical elongate element, the coil being configured to
facilitate coupling of the material to the at least one helical
elongate element.
[0506] A method, including:
[0507] manufacturing an impeller by: [0508] forming a structure
having first and second end portions at proximal and distal ends of
the structure, the end portions being connected to one another by
at least one elongate element; [0509] coiling a coil around the at
least one elongate element; [0510] causing the at least one
elongate element to radially expand and form at least one helical
elongate element, by axially compressing the structure; and [0511]
coupling a material to the at least one helical elongate element,
such that the at least one helical elongate element with the
material coupled thereto defines a blade of the impeller, [0512]
the coil being configured to facilitate coupling of the material to
the helical elongate elements.
[0513] Some examples of such applications are described hereinabove
with reference to FIGS. 3A-K.
[0514] Apparatus including:
[0515] an impeller, including: [0516] an impeller frame that
includes proximal and distal end portions and at least one helical
elongate element that winds from the proximal end portion to the
distal end portion; [0517] a material that is coupled to the at
least one helical elongate element, such that the at least one
helical elongate element with the material coupled thereto defines
a blade of the impeller; and [0518] a sleeve disposed around the at
least one helical elongate element, the sleeve being configured to
facilitate coupling of the material to the at least one helical
elongate element.
[0519] A method, including:
[0520] manufacturing an impeller by: [0521] forming a structure
having first and second end portions at proximal and distal ends of
the structure, the end portions being connected to one another by
at least one elongate element; [0522] placing a sleeve around the
at least one elongate element; [0523] causing the at least one
elongate element to radially expand and form at least one helical
elongate element, by axially compressing the structure; and [0524]
coupling a material to the at least one helical elongate element,
such that the at least one helical elongate element with the
material coupled thereto defines a blade of the impeller, [0525]
the sleeve being configured to facilitate coupling of the material
to the helical elongate elements.
[0526] Some examples of such applications are described hereinabove
with reference to FIGS. 3A-K.
[0527] Apparatus including:
[0528] an impeller, including: [0529] an impeller frame that
includes proximal and distal end portions and at least one helical
elongate element that winds from the proximal end portion to the
distal end portion, the helical elongate element having a rounded
cross-section; and [0530] a material that is coupled to the at
least one helical elongate element, such that the at least one
helical elongate element with the material coupled thereto defines
a blade of the impeller; and [0531] the roundness of the helical
elongate element being configured to cause the material to form a
layer having a substantially uniform thickness at an interface of
the material with the helical elongate element.
[0532] A method, including:
[0533] manufacturing an impeller by: [0534] forming a structure
having first and second end portions at proximal and distal ends of
the structure, the end portions being connected to one another by
at least one elongate element, the elongate element having a
rounded cross-section; [0535] causing the at least one elongate
element to radially expand and form at least one helical elongate
element, by axially compressing the structure; and [0536] coupling
a material to the at least one helical elongate element, such that
the at least one helical elongate element with the material coupled
thereto defines a blade of the impeller, [0537] the roundness of
the helical elongate element being configured to cause the material
to form a layer having a substantially uniform thickness at an
interface between the material and the helical elongate
element.
[0538] Some examples of such applications are described hereinabove
with reference to FIGS. 3A-K.
[0539] A method, including:
[0540] manufacturing an impeller by: [0541] forming a structure
having first and second end portions at proximal and distal ends of
the structure, the end portions being connected to one another by
at least one elongate element; [0542] causing the at least one
elongate element to radially expand and form at least one helical
elongate element, by axially compressing the structure; [0543]
looping a first end of a looped elongate element around the helical
elongate element, the looped elongate element having a predefined
length and being substantially non-stretchable; [0544] inserting a
spring along an axis defined by the first and second end portions,
such that a second end of the looped elongate element is looped
around the spring; [0545] coupling a material to the at least one
helical elongate element and the spring, such a film of material is
supported between the helical elongate element and the spring, the
film of material defining a blade of the impeller, [0546] the
looped elongate element being configured to maintain the helical
elongate element within a given distance from the spring.
[0547] Some examples of such applications are described hereinabove
with reference to FIGS. 3A-K.
[0548] Apparatus including:
[0549] a left ventricular blood pump including: [0550] an impeller;
[0551] a motor configured to drive the impeller to pump blood from
a left ventricle of a subject to an aorta of the subject by
rotating the impeller; and [0552] a computer processor configured
to measure power consumption by the motor that is required to
rotate the impeller at a given rotation rate, and to determine left
ventricular blood pressure of the subject at least partially in
response thereto.
[0553] Some examples of such applications are described hereinabove
with reference to FIG. 9.
[0554] Apparatus including:
[0555] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including: [0556] a blood-pump tube configured such
that a proximal portion of the tube traverses an aortic valve of
the subject, and a distal portion of the tube is disposed within a
left ventricle of the subject, the tube defining at least one blood
inlet opening that is configured to be disposed within the left
ventricle and at least one blood outlet opening that is configured
to be disposed within an aorta of the subject; [0557] an impeller
configured to pump blood through the tube from the subject's left
ventricle to the subject's aorta, by pumping the blood into the
tube via one or more blood inlet openings that are defined by the
tube and that are disposed within the subject's left ventricle, and
by pumping blood out of the tube via one or more blood outlet
openings that are defined by the tube and that are disposed within
the subject's aorta; [0558] a drive cable configured to extend from
the impeller to outside the subject's body; [0559] one or more
outer tubes within which the drive cable is configured to rotate;
[0560] a motor disposed outside the subject's body and configured
to drive the impeller to rotate, via the drive cable; and [0561] a
stator configured to reduce rotational flow components from blood
flow through the blood-pump tube, prior to the blood flowing from
the at least one outlet opening, the stator including: [0562] a
frame that is coupled to the one or more outer tubes, within the
blood-pump tube; and [0563] a flexible material that is coupled to
the frame, such that in a non-radially-constrained configuration of
the stator, the stator defines a plurality of curved projections
that extend radially from the one or more outer tubes.
[0564] For some applications, the frame is a self-expandable frame.
Some examples of such applications are described hereinabove with
reference to FIGS. 14A-C.
[0565] Apparatus including:
[0566] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including: [0567] a blood-pump tube configured such
that a proximal portion of the tube traverses an aortic valve of
the subject, and a distal portion of the tube is disposed within a
left ventricle of the subject, the tube defining at least one blood
inlet opening that is configured to be disposed within the left
ventricle and at least one blood outlet opening that is configured
to be disposed within an aorta of the subject; [0568] an impeller
configured to pump blood through the tube from the subject's left
ventricle to the subject's aorta, by pumping the blood into the
tube via one or more blood inlet openings that are defined by the
tube and that are disposed within the subject's left ventricle, and
by pumping blood out of the tube via one or more blood outlet
openings that are defined by the tube and that are disposed within
the subject's aorta; [0569] the blood-pump tube defining a stator
that is configured to reduce rotational flow components from blood
flow through the blood-pump tube, prior to the blood flowing from
the at least one outlet opening.
[0570] For some applications, the stator includes one or more
curved ribbons that curve within the blood-pump tube. For some
applications, the stator includes a plurality of ribbons disposed
within the blood-pump tube, such as to separate the blood-pump tube
into a plurality of compartments. For some applications, the stator
includes a portion of the blood-pump tube that includes a plurality
of helical tubes. For some applications, the stator includes a
portion of the blood-pump tube that is twisted, such that walls of
the tube define folds that are such as to reduce rotational flow
components from the blood flow through the blood-pump tube, prior
to the blood flowing from the at least one outlet opening. Some
examples of such applications are described hereinabove with
reference to FIGS. 15A-E.
[0571] Apparatus including:
[0572] a blood pump configured to be placed inside a body of
subject, the blood pump including: [0573] an impeller including
proximal and distal bushings; [0574] a frame configured to be
disposed around the impeller; [0575] proximal and distal radial
bearings disposed, respectively, at proximal and distal ends of the
frame; [0576] an axial shaft configured to pass through the
proximal and distal radial bearings and the proximal and distal
bushings of the impeller, [0577] the distal bushing of the impeller
being coupled to the axial shaft, such that the proximal bushing is
held in an axially-fixed position with respect to the axial shaft,
and [0578] the proximal bushing of the impeller not being coupled
to the axial shaft, such that the proximal bushing is not held in
an axially-fixed position with respect to the axial shaft, [0579]
the impeller being configured to pump blood in a proximal
direction, and the impeller being configured to shorten axially by
the proximal bushing sliding distally with respect to the axial
shaft, in response to pressure exerted upon the impeller as a
result of pumping of blood by the impeller.
[0580] Some examples of such applications are described hereinabove
with reference to FIGS. 11A-C.
[0581] Apparatus including:
[0582] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including: [0583] a blood-pump tube configured such
that a proximal portion of the tube traverses an aortic valve of
the subject, and a distal portion of the tube is disposed within a
left ventricle of the subject, the tube defining at least one blood
inlet opening that is configured to be disposed within the left
ventricle, at least one blood outlet opening that is configured to
be disposed within an aorta of the subject, and a central
cylindrical portion; [0584] an impeller configured to pump blood
through the tube from the subject's left ventricle to the subject's
aorta, by pumping the blood into the tube via one or more blood
inlet openings that are defined by the tube and that are disposed
within the subject's left ventricle, and by pumping blood out of
the tube via one or more blood outlet openings that are defined by
the tube and that are disposed within the subject's aorta; [0585] a
pitot tube disposed within the blood-pump tube, the pitot tube
being configured to facilitate measurement of blood flow through
the blood-pump tube, [0586] the blood-pump tube being shaped to
define a region within which the pitot tube is disposed, the region
being disposed within the central, cylindrical portion of the
blood-pump tube, and being narrowed with respect to the central,
cylindrical portion of the blood-pump tube.
[0587] Some examples of such applications are described hereinabove
with reference to FIGS. 17A-D.
[0588] Apparatus including:
[0589] a left-ventricular assist device configured to assist
left-ventricular functioning of a subject, the left-ventricular
assist device including: [0590] a distal impeller disposed within a
first tube, the first tube defining at least one blood inlet
opening, via which the distal impeller is configured to pump blood
into the first tube; [0591] a proximal impeller disposed proximally
with respect to the distal impeller, the proximal impeller being
disposed within a second tube that is disposed in parallel with the
first tube along at least a portion of the first and second tubes,
and the second tube defining at least one blood inlet opening, via
which the proximal impeller is configured to pump blood into the
second tube; [0592] the first and second tubes combining into a
single tube at a location proximal to the proximal impeller, the
single tube being configured to pass through an aortic valve of the
subject, when the distal and proximal impellers are disposed within
a left ventricle of the subject, and the single tube defining at
least one blood outlet opening, via which the distal and proximal
impellers are configured to pump blood into an aorta of the
subject.
[0593] Some examples of such applications are described hereinabove
with reference to FIGS. 30-31.
[0594] Apparatus including:
[0595] a blood pump configured to be placed inside a body of
subject, the blood pump including: [0596] an impeller including
proximal and distal bushings; [0597] a frame configured to be
disposed around the impeller; [0598] proximal and distal radial
bearings disposed, respectively, at proximal and distal ends of the
frame; [0599] an axial shaft configured to pass through the
proximal and distal radial bearings and the proximal and distal
bushings of the impeller, [0600] a first one of the bushings of the
impeller being coupled to the axial shaft, such that the first
bushing is held in an axially-fixed position with respect to the
axial shaft, and [0601] a second one of the bushings of the
impeller not being coupled to the axial shaft, such that the second
bushing is configured to slide axially with respect to the axial
shaft, [0602] the second bushing including a protrusion that
protrudes from its inner surface, and the axial shaft defining a
slot in its outer surface, [0603] the protrusion from the inner
surface of the second bushing being configured to slide along the
slot defined by the outer surface of the axial shaft, such as to
prevent the second bushing from rotating with respect to the axial
shaft as the second bushing slides axially with respect to the
axial shaft.
[0604] For some applications, the slot defined by the outer surface
of the axial shaft defines a stopper at its end, the stopper being
configured to prevent the second bushing from sliding beyond the
stopper, by preventing axial motion of the protrusion from the
inner surface of the second bushing beyond the stopper. Some
examples of such applications are described hereinabove with
reference to FIGS. 6A-E.
[0605] The scope of the present invention includes combining any of
the apparatus and methods described herein with any of the
apparatus and methods described in one or more of the following
applications, all of which are incorporated herein by
reference:
[0606] US 2019/0209758 to Tuval, which is a continuation of
International Application No. PCT/M2019/050186 to Tuval (published
as WO 19/138350), entitled "Ventricular assist device, filed Jan.
10, 2019, which claims priority from: [0607] U.S. Provisional
Patent Application 62/615,538 to Sohn, entitled "Ventricular assist
device," filed Jan. 10, 2018; [0608] U.S. Provisional Patent
Application 62/665,718 to Sohn, entitled "Ventricular assist
device," filed May 2, 2018; [0609] U.S. Provisional Patent
Application 62/681,868 to Tuval, entitled "Ventricular assist
device," filed Jun. 7, 2018; and [0610] U.S. Provisional Patent
Application 62/727,605 to Tuval, entitled "Ventricular assist
device," filed Sep. 6, 2018;
[0611] US 2019/0269840 to Tuval, which is the US national phase of
International Patent Application PCT/IL2017/051273 to Tuval
(published as WO 18/096531), filed Nov. 21, 2017, entitled "Blood
pumps," which claims priority from U.S. Provisional Patent
Application 62/425,814 to Tuval, filed Nov. 23, 2016;
[0612] US 2019/0175806 to Tuval, which is a continuation of
International Application No. PCT/IL2017/051158 to Tuval (published
as WO 18/078615), entitled "Ventricular assist device," filed Oct.
23, 2017, which claims priority from U.S. 62/412,631 to Tuval filed
Oct. 25, 2016, and U.S. 62/543,540 to Tuval, filed Aug. 10,
2017;
[0613] US 2019/0239998 to Tuval, which is the US national phase of
International Patent Application PCT/IL2017/051092 to Tuval
(published as WO 18/061002), filed Sep. 28, 2017, entitled "Blood
vessel tube," which claims priority from U.S. Provisional Patent
Application 62/401,403 to Tuval, filed Sep. 29, 2016;
[0614] US 2018/0169313 to Schwammenthal, which is the US national
phase of International Patent Application PCT/IL2016/050525 to
Schwammenthal (published as WO 16/185473), filed May 18, 2016,
entitled "Blood pump," which claims priority from U.S. Provisional
Patent Application 62/162,881 to Schwammenthal, filed May 18, 2015,
entitled "Blood pump;"
[0615] US 2017/0100527 to Schwammenthal, which is the US national
phase of International Patent Application PCT/IL2015/050532 to
Schwammenthal (published as WO 15/177793), filed May 19, 2015,
entitled "Blood pump," which claims priority from US Provisional
Patent Application 62/000,192 to Schwammenthal, filed May 19, 2014,
entitled "Blood pump;"
[0616] U.S. Pat. No. 10,039,874 to Schwammenthal, which is the US
national phase of International Patent Application
PCT/IL2014/050289 to Schwammenthal (published as WO 14/141284),
filed Mar. 13, 2014, entitled "Renal pump," which claims priority
from (a) U.S. Provisional Patent Application 61/779,803 to
Schwammenthal, filed Mar. 13, 2013, entitled "Renal pump," and (b)
U.S. Provisional Patent Application 61/914,475 to Schwammenthal,
filed Dec. 11, 2013, entitled "Renal pump;"
[0617] U.S. Pat. No. 9,764,113 to Tuval, issued Sep. 19, 2017,
entitled "Curved catheter," which claims priority from U.S.
Provisional Patent Application 61/914,470 to Tuval, filed Dec. 11,
2013, entitled "Curved catheter;" and
[0618] U.S. Pat. No. 9,597,205 to Tuval, which is the US national
phase of International Patent Application PCT/IL2013/050495 to
Tuval (published as WO 13/183060), filed Jun. 6, 2013, entitled
"Prosthetic renal valve," which claims priority from U.S.
Provisional Patent Application 61/656,244 to Tuval, filed Jun. 6,
2012, entitled "Prosthetic renal valve."
[0619] It will be appreciated by persons skilled in the art that
the present invention is not limited to what has been particularly
shown and described hereinabove. Rather, the scope of the present
invention includes both combinations and subcombinations of the
various features described hereinabove, as well as variations and
modifications thereof that are not in the prior art, which would
occur to persons skilled in the art upon reading the foregoing
description.
* * * * *