U.S. patent application number 15/276057 was filed with the patent office on 2017-03-16 for apparatus and procedure for trapping embolic debris.
The applicant listed for this patent is T. Anthony DON MICHAEL. Invention is credited to T. Anthony DON MICHAEL.
Application Number | 20170071720 15/276057 |
Document ID | / |
Family ID | 48141387 |
Filed Date | 2017-03-16 |
United States Patent
Application |
20170071720 |
Kind Code |
A1 |
DON MICHAEL; T. Anthony |
March 16, 2017 |
APPARATUS AND PROCEDURE FOR TRAPPING EMBOLIC DEBRIS
Abstract
A collapsible and deployable filter for blocking debris and
passing blood in a blood vessel in a patient's body, the filter
including; a framework of a flexible material, constructed to have
a radially compressed state, in which the framework is radially
compressed by radial deforming forces, and a radially expanded
state to obdurate an artery; and a flexible filter material secured
to said framework and having pores dimensioned to prevent the
passage of debris therethrough while allowing the passage of blood.
The filter has, in the radially expanded state of the framework, a
generally conical or frustoconical form with a large diameter end,
a small diameter end opposite to the large diameter end, and a side
surface extending between the ends. The filter has an opening that
is free of filter material at the small diameter end or in the side
surface.
Inventors: |
DON MICHAEL; T. Anthony;
(Bakersfield, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DON MICHAEL; T. Anthony |
Bakersfield |
CA |
US |
|
|
Family ID: |
48141387 |
Appl. No.: |
15/276057 |
Filed: |
September 26, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13835816 |
Mar 15, 2013 |
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15276057 |
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PCT/US2012/061038 |
Oct 19, 2012 |
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13835816 |
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61701126 |
Sep 14, 2012 |
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61648311 |
May 17, 2012 |
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61548972 |
Oct 19, 2011 |
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61594669 |
Feb 3, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2/2436 20130101;
A61F 2/24 20130101; A61F 2002/018 20130101; A61F 2230/0067
20130101; A61F 2/013 20130101; A61F 2230/008 20130101 |
International
Class: |
A61F 2/01 20060101
A61F002/01; A61F 2/24 20060101 A61F002/24 |
Claims
1. A device for trapping debris produced during a surgical
procedure performed on a patient, said device comprising: a
collapsible and deployable filter for blocking debris and passing
blood in a blood vessel in a patient's body, a guidewire connected
to said filter, and a sheath in which said filter is housed, said
filter comprising; a framework of a flexible material, said
framework being constructed to have a radially compressed state, in
which said framework is radially compressed by radial deforming
forces, and a radially expanded state; and a flexible filter
material secured to said framework and having pores dimensioned to
prevent the passage of debris therethrough while allowing the
passage of blood, wherein: said filter has, in the radially
expanded state of said framework, a generally conical form with a
large diameter end, a closed end opposite to said large diameter
end, and a side surface extending between said large diameter end
and end; said flexible filter material covers the entirety of said
side surface from said large diameter end to said closed end; and
said large diameter end is open to receive blood and debris and is
dimensioned to prevent flow of blood between said large diameter
end and the blood vessel wall when said framework is in the
radially expanded state; said sheath having a distal end and having
a length and flexibility sufficient to extend through the patient's
blood vessels and heart from a point outside the patient's body to
the patient's pulmonary artery; said guidewire extending through
said sheath and having a distal end connected to said closed end of
said filter with said filter being oriented, wherein said filter is
extendable from said distal end of said sheath and is movable, with
the aid of said guidewire, between said radially compressed state
within said sheath and said radially expanded state when said
filter is extended from said distal end of said sheath, and said
filter is oriented such that said large diameter end faces said
distal end of said sheath when said filter is extended from said
distal end of said sheath.
2. A method for blocking debris in a pulmonary artery of a patient
undergoing a surgical procedure on the heart, using said device as
defined in claim 1, said method comprising: advancing said sheath
with said filter in the radially compressed state within said
sheath, through a vein and the heart of the patient to bring said
distal end of said sheath into the pulmonary artery of the patient;
bringing said filter to a location in the pulmonary artery of the
patient outside of said distal end of said sheath to move said
filter to the radially expanded state; performing the surgical
procedure; and after the surgical procedure, withdrawing said
device from the patient's body.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an apparatus and procedure
for aiding medical treatments in the blood circulation system of a
patient, and in particular for preventing the circulation of
embolic debris, or blood clots, resulting from such treatments. The
invention is primarily, but not exclusively, concerned with
providing protection in connection with procedures like those for
implanting a prosthetic heart valve.
[0002] There are known procedures, known as transcatheter aortic
valve implantation (TAVI), in which a prosthetic heart valve is
implanted at the site of a defective native valve, or of a
previously implanted defective prosthetic valve. In these
procedures, the new prosthetic valve and its guiding structure are
introduced by a transcutaneous catheterization technique. For
example, for implanting a prosthetic aortic heart valve, the valve
and delivery components will be introduced through an incision in
the groin or arm and along a blood vessel path to the desired
location.
[0003] Such a procedure is disclosed, for example, in U.S. Pat. No.
7,585,321, which issued to Alan Cribier on Sep. 8, 2009, the entire
disclosure of which is incorporated herein by reference. Such
valves and their associated guiding devices are marketed by
Medtronic and by Edwards Lifesciences, one example of the Edwards
valves being marketed under the trade name Sapien.
[0004] Although such prosthetic valves have been used successfully
to provide a replacement for stenotic native heart valves or
defective prosthetic valves, the implantation procedure can result
in the creation of embolic debris, which will flow downstream
through the circulatory system and will, in a certain percentage of
cases, cause blockages in smaller blood vessels.
BRIEF SUMMARY OF INVENTION
[0005] The present invention provides an apparatus and procedure to
prevent the circulation of embolic debris resulting from procedures
carried out in the blood circulatory system, one such procedure
being, for example, the implantation of a prosthetic heart
valve.
[0006] To this end, the invention provides a novel filter and a
novel combination of such filter and a blocking device for trapping
embolic debris produced during such a medical procedure. It also
provides the filter with a central, or axial, orifice through which
the valve implantation device, or system, can be directed, which
facilitates this process and reduces the traumatic effects of the
valve implantation device on the wall of the aorta. Since it is
known that trauma to the aortic wall generates clots and calcium,
the position of the orifice in the filter acts as a landmark and
facilitates atraumatic entry of the valvular device.
[0007] The invention also provides, together with the filter and
blocking device, a stent or stent graft that is preliminarily
deployed against the inner wall of the blood vessel, e.g., the
aorta, to prevent trauma during introduction of the filter.
[0008] In further accordance with the invention, the filter can be
delivered in, deployed from and retracted into, a known radially
expandable sheath provided particularly to facilitate retraction of
the filter.
[0009] In further accordance with the invention, there is provided
a filter system for preventing the flow of debris in the pulmonary
artery during heart surgery, such as congenital heart surgery.
[0010] The components of embodiments of the invention may be
conveyed to the treatment site along various blood vessel paths and
may all be introduced via the same path or via respectively
different paths. For example, if the components are to be
positioned in, or pass through, the aorta, the, or each, component
can be introduced through an incision in a groin and the associated
femoral artery, or through an incision in an arm and the associated
subclavian artery.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective view of an embodiment of a filter
according to the present invention.
[0012] FIG. 2 is a perspective and partly cross-sectional view of
the filter shown in FIG. 1, together with related components and a
heart valve delivery system.
[0013] FIGS. 3 and 4 are views similar to those FIGS. 1 and 2 of a
second embodiment of the present invention.
[0014] FIG. 5 is a cross-sectional view relating to a third
embodiment of the invention.
[0015] FIG. 6 is a view, partly in cross section and partly
perspective, showing the third embodiment of the invention.
[0016] FIG. 7 is a perspective view relating to a fourth embodiment
of the invention.
[0017] FIG. 8 is a detail view of a component of the fourth
embodiment of the invention.
[0018] FIG. 9 is a pictorial view showing the fourth embodiment of
the invention.
[0019] FIG. 10 is a perspective view of a further embodiment of a
filter according to the invention.
[0020] FIG. 11 is a pictorial view, partly in perspective and
partly in cross section, of a further embodiment of the
invention.
[0021] FIG. 12 is a pictorial view, partly in perspective and
partly in cross section, of a further embodiment of the
invention.
[0022] FIGS. 13 and 14 are pictorial views of an embodiment of the
invention for blocking debris in the pulmonary artery.
DETAILED DESCRIPTION OF THE INVENTION
[0023] FIG. 1 illustrates one embodiment of a filter 2 according to
the invention composed of a wire framework 4, made of a memory
metal such as nitinol, and a filter fabric 6 of appropriate pore
size, supported by a framework 4.
[0024] Filter 2 has a generally cylindrical structure with a small
diameter end, at the top in FIG. 1, and a large diameter end, at
the bottom in FIG. 1. In the expanded state of filter 2, the
diameter of the small diameter end can be in the range of 18-26 mm
and the maximum diameter of the large diameter end can be of the
order of 35 mm.
[0025] According to a presently preferred embodiment of the
invention, the large diameter end of filter 2 is formed to have a
generally oval shape with a major diameter of about 40 mm and a
minor diameter of the order of 30 mm. This allows the lower end of
the filter to better conform to the somewhat oval shape of a normal
aorta.
[0026] Of course, the dimensions of filter 2 can be varied to
conform to aortas having different sizes, for example in
children.
[0027] Filter 2 has a form defined by an outwardly bowed arcuate
generatrix of rotation about the longitudinal axis of filter 2 such
that the wall of the filter bows outwardly, as shown in FIG. 1.
[0028] The framework of the illustrated embodiment is composed of a
single wire that includes a ring 4a at the small diameter end, a
series of longitudinal struts, or ribs, 4b, and a control portion
4c that extends to a location outside of the patient's body to
allow the position of filter 2 to be controlled by medical
personnel. The framework further includes a circumferential band 4d
at a location between the small diameter end and the large diameter
end. The framework may also include a circular or oval nitinol ring
extending around the large diameter end and bonded to the lower
ends of ribs 4b.
[0029] Filters composed of a framework of memory metal, e.g.
nitinol, wires can be constructed to present a radial
expansion/compression ratio of 8:1, or more. Therefore, they will
be held, in a compressed state in a sheath or tube having an inner
diameter preferably equal to or greater than 1/8 the desired
expanded diameter of the large diameter end of the filter.
[0030] While FIG. 1 shows the framework to be provided with four
ribs 4b, a filter framework in accordance with the present
invention can have many other configurations and can, for example,
be provided with six or more ribs 4b. The framework can also be
made of individual wires that are soldered or otherwise secured
together. In addition, control portion 4c can be a single wire or
can be composed of two, four, or more wires, each connected to ring
4a at a respective location such that the wires are distributed,
preferably at uniform intervals, around ring 4a.
[0031] The structure shown in FIG. 1 further includes a guidewire
10 having a distal end soldered or otherwise secured to the
interior surface of band 4d. The purpose of guidewire 10 will be
explained below with reference to FIG. 2.
[0032] Filter fabric 6 can be of any medically acceptable material
having appropriate mechanical properties and pore size suitable for
trapping debris while allowing the passage of blood therethrough.
Examples of suitable materials for the framework and the filter
fabric are described in, for example, U.S. Pat. No. 7,214,237, the
entire disclosure of which is incorporated herein by reference.
[0033] FIG. 2 illustrates all of the components of a system for
implanting a prosthetic aortic heart valve while preventing the
passage of embolic debris.
[0034] The components shown in FIG. 2 will be described in
conjunction with a description of the manner in which they are
used.
[0035] In FIG. 2, filter 2 is shown in position in the patient's
aorta 20 with the base, or large diameter end, of filter 2 located
downstream of to the defective aortic valve 36.
[0036] The apparatus associated with filter 2 includes a guidewire
30 that is introduced transcutaneously and then along a blood
vessel path into the aorta and through the center of the native or
previously implanted heart valve. Guidewire 30 is then used to
guide the introduction of a sheath, or tube, 32 along the same
blood vessel path and into aorta 20 to bring the distal end of
sheath 32 adjacent the existing valve. During introduction, filter
2 is collapsed within sheath 32. Then, when sheath 32 has been
brought into the desired position in aorta 20, for example adjacent
the interface between the aorta and the existing heart valve,
guidewire 30 can be withdrawn and sheath 32 can be withdrawn, at
least by a distance to not interfere with the valve implantation
procedure, while filter 2 is held in place by acting on control
portion 4c, or the plural control wires, from outside the patient's
body so that filter 2 is freed from sheath 32. Filter 2 is thus
automatically deployed, or expanded, and placed in the position and
configuration shown in FIG. 2, where the large diameter end of
filter 2 is preferably downstream of the coronary artery entrances
to assure that blood flow to those arteries will not be impeded by
debris accumulating on fabric 6. However, filter 2 may
alternatively be deployed at a location above the coronary
arteries, close to the descending aorta.
[0037] Sheath 32 also contains a catheter 40 provided at its distal
end with a low compliance, or noncompliant, blocking balloon 44.
Catheter 40 also includes, in a conventional manner, a balloon
inflation lumen in communication with balloon 44. Catheters
provided with such lumens are well known in the art. One example
being U.S. Pat. No. 7,169,171, the entire disclosure of which is
incorporated herein by reference. Catheter 40 may have a diameter
as small as 4 Fr. (1.3 mm).
[0038] After filter 2 has been deployed, catheter 40 is advanced
along guidewire 10 to bring balloon 44 to the location 44a shown in
broken lines in FIG. 2. At this time, balloon 44 may be partially
of fully deflated. After balloon 44 has been brought to position
44a, it may be partially inflated by introduction of a radioactive
contrast, or radiopaque, fluid, the purpose of which will be
described below.
[0039] At a time after filter 2 has been deployed, guidewire 30 and
sheath 32 can be withdrawn from the patient's body.
[0040] Then, an assembly 60 for implanting the prosthetic heart
valve is introduced into the aorta, preferably, but not
necessarily, via a different blood vessel path, by first passing a
guidewire 62 along that blood vessel path through the center of
filter 2 and through the existing heart valve. Assembly 60
includes, in addition to guidewire 62, a sheath, or tube, 64 and a
system 66 including the prosthetic heart valve and components for
deploying it
[0041] After guidewire 62 is put in place, tube 64 is introduced
into the aorta over guidewire 62 to a location adjacent filter 2,
after which system 66 is extended out of tube 64 and through ring
4a of filter 2 and along the central orifice defined by filter 2,
for implanting the prosthetic heart valve. System 66 and one
suitable manner in which it is used to implant a prosthetic heart
valve are all described in detail in U.S. Pat. No. 7,585,321, the
entire disclosure of which is incorporated herein by reference.
[0042] Valve assembly 60 can be inserted by puncturing an artery in
the groin and advancing it upwards through the femoral artery and
the aorta, followed by advancing system 66 through the existing
valve.
[0043] The valve assembly could also be introduced through either
the right or left subclavian artery, which normally supplies an
upper extremity. Consequently, there is the option of introducing
sheath 32 and filter 2 through either subclavian artery or through
the femoral artery. In general, it is presently preferred to use
one of these paths, the subclavian artery or femoral artery, for
introducing sheath 32, and the other of these paths for valve
assembly 60. Since sheath 32 can have a smaller diameter, it might
be advantageous to advance it through the subclavian artery
path.
[0044] It is presently believed by workers in the art to not be
desirable to use the same route for introducing both the valve
implantation assembly and the filter assembly due to the fact that
every trial done so far has criticized the valve assembly alone as
being relatively thick and traumatic in the process of puncturing
the artery. The only acceptable single route, which is not favored
by patients, is to puncture the heart. For all these reasons, the
diameter of valve assembly 60 has been reduced in Europe to 18 mm,
although this is not yet approved by the USFDA.
[0045] It is important to note that the valve assembly is a
cylindrical, relatively rigid structure below which the valve
hangs, crimped on an angioplasty balloon, and that expansion of the
valve is produced by inflating the angioplasty balloon in the case
of the Edwards device and by pulling on the valve using nitinol
bands in the case of a Medtronic device.
[0046] Neither of these techniques interferes with the use of the
filter assembly according to the present invention, which serves to
isolate the carotids and other parts of the blood circulatory
system from debris that is released during and after implantation
of the prosthetic valve, regardless of which valve implantation
technique is used.
[0047] During implantation of the heart valve, tube 64 can bear
against the opening at the top of filter 2 to help prevent the
passage of embolic debris and to stabilize the position of the
filter. Filter 2, sheath 32 and wire 10 are oriented to cause wire
10 to extend into filter 2, adjacent ring 4a, at a location to not
interfere with the positioning of tube 64.
[0048] Balloon 44 may be partially inflated with radioactive
contrast fluid before withdrawal of the components 66 for
implanting the heart valve and tube 64; and immediately after
withdrawal of those components, balloon 44 is further inflated, if
this was not previously done, and pulled back by acting on catheter
40 from outside the patient's body to cause balloon 44 to block the
small diameter opening of filter 2. The presence of radioactive
contrast fluid allows the position of balloon 44 to be monitored
fluoroscopically.
[0049] Inflated balloon 44 acts to close the smaller diameter hole
in filter 2 as soon as the prosthetic valve introduction system is
retracted out of the filter, thus enabling debris to be trapped
adjacent the smaller diameter end of the filter.
[0050] Then, after a suitable period of time has elapsed, during
which debris can become trapped in filter 2, filter 2 and balloon
44 are drawn into sheath 32 by pulling on control portion 4c, or
the plural control wires, if provided, and catheter 40 and tube 64,
along with all of the associated components, are withdrawn from the
patient's body.
[0051] More specifically, balloon 44 will remain inflated and
lodged in the smaller diameter opening of filter 2 during an
initial phase of withdrawal so that filter 2 and catheter 40 will
be pulled toward sheath 32 as a unit. Then, when the smaller
diameter end of filter 2 reaches sheath 32, balloon 44 will be
deflated and catheter 40 may be partially or fully retracted so
that balloon 44 moves out of contact with filter 2. Then, filter 2
can be retracted into sheath 32; and then sheath 32, containing
catheter 40 and filter 2, can be fully withdrawn from the patient.
During this withdrawal procedure, suction may be applied through
sheath 32 to assist the removal of any embolic debris from filter
2.
[0052] As an alternative to using a wire 10 to introduce balloon
catheter 40, it would be possible to simply use a small diameter
catheter with a balloon at the end, surrounding the catheter wall
and communicating with a balloon inflation lumen formed in the
catheter, to close the opening, or orifice, at the top of filter 2
as soon as valve assembly 60 is pulled out of the filter, thereby
preventing escape of emboli. This small diameter catheter may be
introduced with the aid of a guidewire that extends though the
catheter.
[0053] The fact that filter 2 is open at the top offers the
advantage of preventing the filter from being blown out of position
by the relatively forceful blood flow being produced by the heart
as it pumps the blood.
[0054] The radiopaque fluid used to inflate balloon 44 will enable
the balloon to be readily observed.
[0055] Inflated balloon 44 will also serve as a means for partially
altering the configuration of the filter and making it parallel to
and in line with sheath 32 to facilitate retraction of filter 2
into sheath 32 after completion of the procedure.
[0056] FIGS. 3 and 4 show a filter 72 according to a second
embodiment of the invention that can provide improved protection
against the escape of embolic debris. Filter 72 has a generally
cylindrical structure, at least when expanded, and is composed of a
framework presenting two portions: a lower portion between a ring
74a at the lower end of the filter and a ring 74c at the upper end
of the lower portion; and an upper portion extending between ring
74c and a ring 74f at the upper end of the filter.
[0057] The lower portion is also composed of a series of
longitudinal struts, or ribs, 74b extending between rings 74a and
74c, and a circumferential band 74d at a location between rings 74a
and 74c. Preferably, as in the case of the embodiment of FIGS. 1
and 2, ring 74a is shaped so that in its expanded, or deployed,
state, it has an oval form with major and minor diameters of the
order of 40 mm and 30 mm, respectively.
[0058] Struts 74b, like struts 4b of FIGS. 1 and 2, are preformed
to curve in the manner illustrated when the filter is deployed, in
which case the external surfaces of struts 74b are outwardly
convex.
[0059] The upper portion of filter 72, between rings 74c and 74f,
is provided with a plurality of longitudinal struts, or ribs, 74e.
Preferably, struts 74e curve in the opposite direction from struts
74d so that struts 74e are outwardly concave when the filter is
deployed. However, struts 74e can also be constructed to have a
straight form when the filter is deployed.
[0060] The framework of filter 72 is completed by, preferably, four
wires 74g constituting a control portion performing the same
function as control portion 4c shown in FIGS. 1 and 2. The
provision of four wires 74g allows for the possibility of
controlling the positioning of the filter in the aorta.
[0061] Like the embodiment shown in FIGS. 1 and 2, the filter shown
in FIGS. 3 and 4 includes guidewire 10 whose distal may be soldered
or otherwise secured to the inner surface of band 74d. The purpose
of guidewire 10 is essentially the same of that of the guidewire 10
described with reference to FIGS. 1 and 2.
[0062] Also like the embodiment of FIGS. 1 and 2, a filter fabric
is suitably secured to and supported by the framework composed of
components 74a-74f. Also as in the case in the embodiment shown in
FIGS. 1 and 2, there is no fabric in the planes enclosed by rings
74a and 74f.
[0063] Also shown in FIG. 3, in broken lines, is the distal end of
tube 64. At least ring 74f is dimensioned to allow entry of tube 64
into the region enclosed by filter 72 and wires 74g. Ring 74f, in
the deployed state of filter 72, could have a larger diameter than
ring 74c if needed to accommodate tube 64.
[0064] Preferably, ring 74f is dimensioned to provide a close fit
with tube 64. Optionally, the distal end of tube 64 can be slightly
tapered to allow introduction of tube 64 into the upper portion of
filter 72, while assuring the establishment of a tight fit with
ring 74f, and possibly to provide a sealed connection between tube
64 and ring 74f, thereby preventing the escape of embolic debris
from filter 72 during valve implantation.
[0065] The manner in which filter 72 is used will be explained with
reference to FIGS. 2, 3 and 4.
[0066] Filter 72 is employed together with system 60, sheath 32,
catheter 40 and low compliance or noncompliant balloon 44, all of
which are shown in FIG. 2, and the operation of which has been
described above.
[0067] After filter 72 has been installed and positioned to
surround the entire region through which the replacement valve will
be deployed, catheter 40 carrying balloon 44 is advanced over
guidewire 10 to the location shown in FIG. 4 and tube 64 is
introduced over guidewire 62 so that the distal end of tube 64
penetrates at least the upper part of the upper portion of filter
72, and preferably forms a seal with ring 74f. Tube 64 and catheter
40 essentially block the upper end of the upper portion of filter
72. Since catheter 40 has a relatively small diameter, of the order
of 1 mm, only a minimal gap will exist at the top of upper portion
of filter 72 so that escape of debris from filter 72 will be
minimal, if any.
[0068] Then, system 66 is operated to install the replacement heart
valve.
[0069] At the completion of this operation, after system 66 has
been withdrawn back into tube 64, balloon 44 is at least partially
inflated and catheter 40 is withdrawn to bring balloon 44 into
contact with ring 74c. Before or after balloon 44 has been brought
to the proper position, it may be further inflated in order to form
a tight seal at the location of ring 74c. Then assembly 60 can be
fully withdrawn, after which filter 72, with balloon 44 still in
place and inflated, begins to be withdrawn into sheath 32 by
pulling on control wires 74g.
[0070] After the top portion of filter 72 has been introduced into
sheath 32, balloon 44 is deflated while, preferably, suction is
produced within sheath 32 in order to withdraw any debris being
held within filter 72.
[0071] After deflation of balloon 44, filter 72 and catheter 40 are
completely withdrawn into sheath 32, and sheath 32 can then be
withdrawn from the patient's body.
[0072] The invention as described above offers a number of other
advantages. For example, it will allow injection of clot lysing
material into the filter and if catheter 40 is provided with an
orifice above filter 2, it can be used to continuously monitor the
arterial blood pressure.
[0073] The filter disclosed herein may also be used to trap embolic
debris, or blood clots, in other procedures, such as in treating
children or young adults with congenital heart disease who have
pulmonary stenosis and on whom is performed a similar procedure
that may generate blood clots.
[0074] In FIGS. 2 and 4, a catheter carrying a blocking balloon and
a tube 64 for the valve delivery system both pass through the
opening at the top of the filter. While it is obvious that there
will be a gap present around the catheter, the size of the gap
would be no more than approximately 1/24 of the diameter of tube
64. However, in the case of filter 72, balloon 44 will form a
near-perfect seal with ring 74c. both before the withdrawal of
system 66 carrying the valve and thereafter. The technique would be
to inflate the balloon at the junction with the valve carrying
device and track both these structures upwards during their
withdrawal. At a time not later than the point in the procedure
when the valve delivery sheath is about to exit the bottleneck, the
balloon would be fully expanded to completely close the orifice
through which it is retracted, thereby preventing escape of emboli
both in the early and late phases of valve/sheath withdrawal. When
this is accomplished, and the sheath of the valve is separated from
the bottle neck carrying the balloon, the correct procedure would
be to advance sheath 32 carrying the bottleneck from the side
arising from the subclavian artery and collapse the balloon and
catheter into sheath 32. The balloon would have appropriate
consistency which allows it to be optimally in contact with the
nitinol sheath; if it is underinflated or has a low pressure it may
not prevent emboli from going upwards between the balloon and
nitinol sheath. If it is excessively stiff and at a high pressure,
it could stretch and damage the nitinol filter.
[0075] Balloon 44 should be one with a reasonably low compliance
such that it does not rupture and does not expand the bottle neck,
which is preferably made of nitinol but has a firm surface.
[0076] The components of the embodiment shown in FIGS. 3 and 4 can
be introduced into the aorta over the same paths as described with
reference to the embodiment of FIGS. 1 and 2.
[0077] A further embodiment of the invention is shown in FIGS. 5
and 6.
[0078] According to this embodiment, components 60 and 80, to be
described below, can be introduced along the same path, for example
along the femoral artery and into the aorta via an incision made in
the groin, or through one subclavian artery, as described earlier
herein.
[0079] The components shown in FIG. 5 include a guidewire 62 that
is introduced first into the ascending aorta (20 in FIG. 2), to a
point close to the valve that is to be replaced, or to a point
above the coronary arteries. Then, guidewire 62 is used to
introduce a first sheath 64, which may have a diameter of the order
7 mm, and the distal end of sheath 64 is also brought to a point in
the ascending aorta, after which guidewire 62 may be withdrawn, and
a second sheath 68, which may have a diameter of the order of 6 mm,
is introduced into sheath 64.
[0080] Sheath 68 contains a filter 80 somewhat similar to filter 2
shown in FIGS. 1 and 2. In the illustration provided in FIG. 5,
filter 80 is held in a radially compressed state in sheath 68.
[0081] Filter 80, which will be described in greater details below
with reference to FIG. 6, is provided with two control wires 82
that extend through sheath 68 to a location outside of the
patient's body.
[0082] After sheath 64 has been brought to its desired position in
the aorta, sheath 68 will be advanced to bring its lower, or
distal, end to a location close to the defective heart valve, at
least approximately where the lower end of filter 80 is to be
deployed. Then, sheath 68 is retracted while filter 80 is held in
place by a holding force, possibly manual, on control wires 82. As
filter 80 thus exits the lower end of sheath 68, the filter expands
while it is being deployed to bring it to the desired position to
collect debris.
[0083] Then, sheath 68 may be withdrawn from the patient's
body.
[0084] Referring now to FIG. 6, which shows filter 80 in its
deployed state, it will be seen that filter 80 is compose
essentially of a framework that includes an upper ring 84, a lower
ring 86 and longitudinal struts 87, all preferably made of a type
of a memory metal such as nitinol. The sides of filter 80 are
covered with a suitable filter fabric having a pore size of, for
example, 110 .mu.m. Filter 80 is open at the top and the bottom and
has a generally frustoconical shape when deployed.
[0085] Filters having a nitinol frame can generally expand radially
by a maximum factor of 8 and filter 80 is dimensioned so that in
the deployed, or expanded state, lower ring 86 has a diameter of
the order of 32 mm and upper ring 84 has a diameter of the order of
7 mm. Sheath 64 is brought to a position in which, as shown in FIG.
6, the lower end of the sheath 64 contacts ring 84.
[0086] After filter 80 has been thus deployed and sheath 64 has
been brought into the position shown in FIG. 6, a system 66,
described earlier herein, will be introduced through sheath 64 and
then through filter 80, after which system 66 will be operated in a
known manner to implant the prosthetic valve.
[0087] Typically, introduction of system 66 will be aided by a
guidewire such as guidewire 62 shown in FIG. 2 of the application
drawing, which will be introduced in order to guide system 66 past
the defective heart valve.
[0088] During implantation of the heart valve, debris will be
released and this debris will be confined by filter 80 and will be
carried off with blood through sheath 64 to a suction device
located outside of the patient's body. This blood and debris can
pass through at a conventional device such as a Coulter counter,
which detects and counts the debris particles. Suction will be
continued until the output of the measuring device indicates that
no further debris is present in the blood flow.
[0089] With the arrangement shown in FIG. 6, sheath 64 helps to
stabilize the position of filter 80.
[0090] After such an indication has been produced, filter 80 can be
withdrawn, by acting on the control wires 82, into sheath 64 and
all components can then be withdrawn from the patient's body.
[0091] After filter 80 has been deployed at the desired location, a
guidewire (not shown) is introduced, for example through the groin
or the subclavian, and then passed though ring 88 into the region
enclosed by filter 80.
[0092] Outside of the patient's body, debris in the blood exiting
thought the top of filter 80 can be filtered out of the blood and
the filtered blood can be returned to the patient's circulatory
system, as will be described subsequently herein.
[0093] A further embodiment of the invention is illustrated in
FIGS. 7, 8 and 9.
[0094] FIG. 7 shows a filter 90 having a generally conical form
that is open at its large diameter lower end and closed at its
upper end, and the sides of which are covered with filter material,
or fabric, filter 90 thus being in the general form of a cone.
[0095] Filter 90 is provided with a control wire 92 at its apex,
where it is closed. Filter 90 can be introduced through a
subclavian artery, for example the left subclavian artery.
[0096] Filter 90 is provided with an entry cone 100 and a side
opening 104 in which filter fabric is not present. Side opening 104
is closed by a series of flaps of a suitable material, constructed
to normally be closed, together with a tube 108, which may be
corrugated, and which is open at its inner end 112, as shown most
clearly in FIG. 8. Entry cone 100 may be corrugated, as shown, and
dimensioned to bring the distal, or lower, end of cone 100 to the
plane of the open end of filter 80 and to the center of the lower
end.
[0097] Referring to FIG. 9, filter 90 is introduced into position
in ascending aorta 20 by means of a sheath 120 that performs
essentially the same function as sheath 32 shown in FIG. 2, except,
in this embodiment, components 40, 44 and 44a are not provided.
After filter 90 has been deployed, essentially in the manner
described earlier therein, assembly 60 is introduced, possibly
through the femoral artery and the descending aorta, and is
inserted into cone 100 through opening 104. Preferably, cone 100 is
dimensioned so that at least the lower end thereof forms a seal
with tube 64.
[0098] Then, in the manner described previously, for example with
respect to FIG. 2, the guidewire associated with assembly 60 is
introduced through the defective heart valve and assembly 60 is
then operated to implant the new valve.
[0099] During implantation, sheath 120 may be placed in contact
with filter 90 to stabilize the position of the filter.
[0100] After implantation, suction is maintained through tube 64 to
extract debris mixed with blood and, as in the case of the
embodiment of FIGS. 5 and 6, the blood being suctioned is monitored
to determine when all debris has been removed.
[0101] Then, assembly 60 is withdrawn from the patient's body,
filter 90 is retracted into sheath 120, and sheath 120, with
retracted filter 90, is withdrawn from the patient's body.
[0102] According to an alternative valve implantation procedure,
the heart may be punctured at its apex and valve assembly 60 can be
inserted through the puncture opening in the apex from a location
below the existing valve. In this case, the filter structure shown
in FIGS. 7-9 can be used for introducing valve assembly 60 and
catheter 116. Sheath 120 can then be placed in contact with filter
90 to stabilize the position of the filter.
[0103] In further accordance with the invention, a wall stent or
stent graft may be initially deployed to protect the aorta during
valve implantation and an inflatable sheath may be employed in
place of sheath 32 to facilitate retraction of filter 2, 72, 80,
90. In addition, the filter may be provided with additional
structures to control blood flow from the heart in a manner to
assure that the filter is not displaced by the force of the blood
flow. These features will be described in detail below.
[0104] Two well known stent-grafts are: the Cook Zenith Flex graft
and the Medtronics graft for the ascending aorta.
[0105] In each embodiment of the invention, the framework may be
coated or impregnated with radiopaque material, or could be
provided with individual radiopaque studs, or beads, lining the top
and/or the bottom rings of the filter framework to facilitate
guidance of the filter to its desired position and introduction of
wire 62. i.e. guidance of system 66 through the hole at the top of
the filter and into the existing valve.
[0106] Filters according to the present invention may be positioned
to surround the entire circumference of the valve that is deployed,
with the result of preventing blood clots from entering the
coronary arteries.
[0107] In the case of the embodiment shown in FIGS. 7, 8 and 9,
sheath 120 may be introduced through one subclavian artery,
assembly 60 may be introduced through a femoral artery and catheter
116 may be introduced through a radial artery or the other
subclavian artery.
[0108] A further embodiment of the invention is composed of a
debris filter 150, shown in FIG. 10.
[0109] The filter shown in FIG. 10 is somewhat similar to filter 80
shown in FIG. 6. Filter 150 is provided with control wires 152
corresponding in function to control wires 82 shown in FIG. 6.
Filter 150 is composed of an upper ring 154, a lower ring 156
having, in a deployed state of the filter, a larger diameter than
ring 154, and longitudinal struts 158, all of these parts
preferably being made of a type of memory metal such as nitinol.
Upper ring 154 is connected to wires 152. The sides of filter 150
are covered with a suitable filter fabric having a pore size of,
for example, 100 .mu.m, or more generally a pore size that will
permit as free a flow of blood as possible, while retaining embolic
debris within the filter.
[0110] The lower end of filter 150, enclosed by ring 156, is open
to receive blood and debris from the region being treated, such as
the heart valve region and the area of the aortic wall into which
vein bypasses are customarily attached or implanted.
[0111] Filter 150 differs from filter 80 essentially only in that
the upper end of filter 150, enclosed by ring 154, is covered with
the same type of filter fabric as described earlier herein, with a
pore size of, for example 100 .mu.m. The upper end of filter 150
may be provided with a small diameter ring 170 secured to ring 154
by at least four radial spokes 174. The outer ends of spokes 174
are bonded to ring 154 in any suitable manner to secure ring 170 in
place. Ring 170 and spokes 174 may be made of nitinol wires. Filter
fabric is not present in the region enclosed by ring 170.
[0112] Ring 170 is dimensioned to receive a small diameter tube, or
catheter, 176, which may have a diameter of the order of 5-6 Fr.
and is preferably dimensioned to achieve a sufficiently close fit
between ring 170 and tube 176 to prevent the escape of debris
therebetween. Tube 176 may be of a type known as a "pigtail"
catheter.
[0113] After filter 150 has been deployed at the desired location,
a guidewire (not shown) is introduced, for example along the same
path as filter 150, and then passed though ring 170 into the region
enclosed by filter 150. Then tube 176 is passed over the guidewire
and through ring 170, also into the region enclosed by filter
150.
[0114] Filter 150 is provided at its side with a plate 160 provided
with a through opening 162 that is not covered with filter
fabric.
[0115] Tube 176 is employed to inject a contrast fluid that
facilitates visualization of the surgery site, such as the aorta
and the aortic valve. It can also be utilized to work with a TAVI
catheter assembly which is inserted through opening 162. Thus, the
tube 176 and the TAVI catheter can be used simultaneously to permit
observation of the natural valve and to cross it, respectively.
[0116] After the need to inject contrast fluid has ended, tube 176
can be pulled up so that its lower end is still within filter 150
and so that it continues to obturate the opening defined by ring
170. Tube 176 can be connected to a suction device outside the
patient's body to suction debris, inevitable accompanied by blood,
through tube 176. Outside of the patient's body, debris can be
filtered out of the blood and the blood can be returned to the
patient's circulatory system
[0117] The device shown in FIG. 10 is intended to be employed
together with a valve implantation assembly, such as assembly 60
shown in FIG. 2 and described in detail earlier herein.
[0118] A procedure according to the invention, using the devices
shown in FIG. 10, along with a valve implantation assembly is
performed in the following manner.
[0119] A first guidewire is inserted along a blood vessel path to a
point close to the heart valve that is to be replaced and then a
sheath, such as sheath 32 shown in FIG. 2, is advanced over the
guidewire. Then, the guidewire is withdrawn and a filter 150 is
introduced through and out of the sheath to a location
corresponding to that shown in FIG. 2. The delivery of filter 150
is controlled by control wires 152. Filter 150 may be installed
initially in the distal end of sheath 32, prior to introduction of
sheath 32 into the blood vessel. If ring 170 is provided, the first
guidewire cam be inserted through the hole enclosed by ring 170
prior to introduction into the blood vessel. If ring 170 and its
associated hole are not provided, the first guidewire can be
initially threaded through side opening 162 and then through the
blood vessel
[0120] Then, a second guidewire, such as guidewire 62 shown in FIG.
2, is introduced through a blood vessel path and directed through
opening 162. Then, assembly 60 is introduced into the blood vessel
path and tube 64 or system 66 is caused to pass through opening 162
and is operated to implant an artificial valve, as described
above.
[0121] After the valve has been implanted, assembly 60 and
guidewire 62 are removed from the patient's body.
[0122] All of the guidewires employed in the practice of all of the
embodiments disclosed herein may be any commercially available
guidewires intended for use in blood vessels, such as Charter.TM.
Guidewires marketed by Navilyst Medical of Marlborough, Mass.
[0123] The following table lists the blood vessel passages that can
be used for introduction of each of the devices described
above.
TABLE-US-00001 FIG. DEVICE ARTERY 2 32 Subclavian 2A 32 Subclavian
5 62 Subclavian 6 (2A) 32 Subclavian 7 92 Subclavian or femoral 9
60 Femoral 10 (2A) 150 Subclavian 11 180 Femoral
[0124] If, in the procedure described with reference to FIG. 10,
the TAVI assembly and the filter sheath are introduced through the
groin, the pigtail catheter can be introduced through the apex of
the filter similar to that shown in FIGS. 10-12, in which the hole
is located at the top of the filter in the central area within the
upper ring of the filter.
[0125] It is important to point out that the TAVI catheter and the
pigtail catheter are in proximity to each other prior to and
immediately after the valve is implanted. This is an essential part
of the procedure which ensures appropriate positioning during the
process of implanting the valve. It is also to be noted that in
either event, namely, using the subclavian or the groin, due to the
constraints of space, the TAVI catheter assembly 60 and the filter
enter through the same artery, with the filter sheath being
withdrawn from the artery before introduction of the valve
implantation assembly 60, while, the pigtail catheter is introduced
through a different artery. This ensures that the diameter of the
blood vessel in either case is not stretched to the point of
injury.
[0126] In the case of the embodiment shown in FIG. 10, filter 150,
in its introduction sheath, may be introduced through a femoral
artery or a subclavian artery, and the TAVI catheter assembly (60
in FIG. 2) may be introduced through a femoral artery or subclavian
artery different from that used for introducing filter 150. Tube
176 may be introduced through a radial artery.
[0127] A further embodiment of a device incorporating a filter
according to the present invention is illustrated in FIG. 11.
[0128] The embodiment shown in FIG. 11 is intended to be employed
in connection with invasive procedures, such as open heart surgery,
using instruments not introduced through, for example, the
aorta.
[0129] A purpose of this embodiment is to avoid the adverse, and
potentially fatal, effects of bypass surgery caused by the
migration of emboli into the brain, resulting in strokes and
cognitive disorders.
[0130] This embodiment includes a filter 302 that will be deployed
at a location downstream of the surgical site. Filter 302 is
somewhat similar in form to filter 2 shown in FIGS. 1 and 2, filter
302 having a large diameter end 304 and a small diameter end 306,
and the filter being opened, i.e. not provided with filter fabric,
at both ends 304 and 306. Small diameter end 306 is secured to a
suction tube 308.
[0131] Large diameter end 304 may have a deployed diameter of 32-40
mm, while small diameter end 306 and tube 308 may have a diameter
of the order of 4 mm.
[0132] The proximal end of tube 308, i.e. the end that will be
outside of the patient's body, is secured to a filter 312. The
assembly composed of filter 302 and tube 308 may be introduced
through a suitable sheath 320 into an artery to a point downstream
of a location where debris will be produced by the surgical
procedure and upstream of vessels that carry blood to the
brain.
[0133] When filter 302 has been introduced to the desired location
and deployed, and the surgical procedure is being performed, debris
produced by the procedure will be conveyed, along with blood, into
filter 302. A portion of the blood will then pass through the
filter mesh, or fabric, that covers the circumference of filter 302
between ends 304 and 306 while the debris, along with some blood,
will flow through small diameter end 306 and tube 308 to filter
312. In filter 312, debris will be separated from blood and the
filtered blood may then be conducted into an artery or vein to be
returned to the circulatory system. Filter 312 may be constructed
according to principles already well known in the art.
[0134] The device shown in FIG. 11 may be introduced through any
suitable artery. For example, in the case of open heart surgery,
filter 302 may be introduced into the aorta along a path from an
incision in the groin or through the subclavian artery.
[0135] Filter 302 could also be introduced on the right side of the
heart in the pulmonary artery as a potential means of preventing
blood clots from entering the lungs and for right heart surgery.
The device could be introduced in this case through a peripheral
vein.
[0136] In all cases, filter 302 would be deployed downstream from
the locations where emboli would be produced during the surgical
procedure.
[0137] FIG. 12 shows a modified version of the device of FIG. 11
and embodies a filter 402 with an open end 404 at the bottom and an
upper end 406 provided with an opening, similar to that shown in
FIG. 10, but without plate 160 and opening 162. The upper end 406
is closed by filter fabric material and has a central metal ring
providing an orifice and spokes that connect the ring to the upper
end of the filter. The orifice is not covered with filter fabric
and allows the passage of a catheter 408 having a diameter of 5-7
Fr., and preferably 5-6 Fr., which can be introduced through a
sheath 420 that was preliminarily passed through the radial artery
with the aid of a guidewire, and then passed into the filter. This
catheter 408, depending on what is needed, can either be a pigtail
catheter or can be a fiberscope or an ultrasound device which can
be used to view the aorta and the location of the valve and the
walls of the aorta. Thus, this device can be used through its
entrance sheath 420 in the arm to obtain pictorial representations
of the condition of the aorta and the aortic valve, or other part
being treated. This would be done prior to open heart surgery and
could be replaced with a 5-7 F pigtail catheter, which is used to
drain debris exiting from the apex of filter 402. The proximal end
of catheter 408 will be attached, outside the patient's body, to a
3-way stop cock 410 through which contrast fluid can be introduced
from a supply tube 412, or through which debris and blood could be
passed to a filter 414, as described with reference to FIG. 11.
This device will serve to minimize the spread of debris to the
brain and body and enable blood flow to continue through 100 .mu.m
holes in the fabric. Filter 414 could be associated with a suction
device to help suction debris out of filter 402.
[0138] The assembly shown in FIG. 12 differs from those used for
TAVI, i.e, those involving introduction of a replacement heart
valve through the arteries. Sheath 420 and tube 408 can be
introduced through a subclavian artery, or a radial artery in the
arm, or the groin. The exiting debris and blood is passed through
an external filter and the blood is returned into the body as
described in the case of the TAVI filter. This is different from
the debris removal described in connection with TAVI
procedures.
[0139] The assemblies shown in FIGS. 11 and 12 can be introduced
via a femoral artery or a subclavian artery.
[0140] In all of the procedures employing filters according to the
invention, any opposition to deployment and positioning of the
filter can be minimized by temporarily halting or reducing the flow
of blood from the aorta. This can be achieved, for example, by
employing a pacemaker to produce a high pacing rate, for example of
the order of 220 beats/minute.
[0141] The present invention provides the possibility of using at
most two to three entry passages to completely implant and
stabilize the filter, trap and withdraw debris and deploy an
artificial valve. These entry points can be selected from one groin
and the radial artery that leads into the subclavian to carry the
pigtail catheter for introducing contrast fluid, or one groin,
which carries the TAVI catheter and the sheath for implantation of
the filter. In the event that the both groins are blocked and
cannot be used, use can be made of one subclavian to deploy the
filter and TAVI catheter and the other subclavian to introduce and
advance the pigtail catheter. In either of these cases, the ability
exists to perform two processes: To use the TAVI catheter and
filter through a single groin or subclavian and the other to
implant the pigtail catheter through the opposite groin or
subclavian. In either case the ability to use the TAVI catheter
with the filter depends on the ability to initially advance the
filter with its sheath which encloses a guide wire, to deploy the
filter and after this, to withdraw the sheath which surrounds the
guidewire all the way to the origin of the point of insertion of
the filter, thus, creating adequate space to advance the TAVI
catheter with or without its own guide wire alongside this
guidewire and to enter the orifice described in the filter.
[0142] However, the TAVI catheter can be inserted into the right
groin and the filter can be inserted into the left groin or vice
versa or under exceptional circumstances into the right or left
subclavian. It would still be possible to use the radial artery on
the right or left side to implant the pigtail catheter depending on
the points of insertion of the filter and the TAVI catheter. These
circumstances will depend on the recently developed 12 Fr. TAVI
catheters and changes in the expansibility of the modified nitinol
to create the filter. These are currently not in common use.
[0143] Filters according to the present invention can have a radial
expansion ratio of 8:1. If the compressed diameter is, for example,
4.5 mm, the expanded filter can obturate the aorta with a lower
ring such that it is inserted to apply pressure on the
circumference of the aorta to stabilize it.
[0144] The catheter that may be a pigtail catheter can be used both
for injecting contrast fluid for withdrawing debris from the filter
in a safe and sterile way into an artery of the wrist, namely, the
radial, which allows the observer to visually see the debris and
subject it to quantitative and qualitative analysis and/or
filtration. The debris can be analyzed by a cell counter such as a
Coulter counter, which can enable a temporal estimation of debris
production and clearance.
[0145] Relative to the use of a filter on the right side of the
heart, it is possible to use a filter similar to the one described
previously composed of nitinol and fabric and introduced through a
sheath, which filter does not incorporate orifices, or openings, as
previously described. This filter is introduced, enclosed by a
sheath, through a vein which carries blood to the heart and which
is located in an arm, the neck or the legs.
[0146] The sheath and filter can be introduced under fluoroscopic
control into the right side of the heart, traversing one of the two
main veins entering the heart and is manipulated under fluoroscopic
control into the pulmonary artery which supplies the lungs. The
filter is deployed in a similar manner by withdrawing the sheath
and allowing it to stabilize in the pulmonary artery. Since the
pulmonary artery divides into left and right branches, these
arteries to the left and right lung are protected from emboli. This
technique is particularly applicable in cardiac surgery for
congenital heart disease to prevent blood clots from entering the
lungs, which is a known complication of this type of surgery. The
filter is deployed and removed using the same techniques explained
above with the TAVI filter and the other described filters, namely,
by pulling the filter into a sheath to close it or expressing the
filter out of the sheath, to deploy it.
[0147] FIGS. 13 and 14 illustrate a further embodiment of the
invention for blocking the flow of debris through the pulmonary
artery during a surgical procedure performed on the heart, such as
congenital heart surgery.
[0148] As shown in FIGS. 13 and 14, this embodiment includes a
sheath 512 having a diameter selected to be compatible with the
dimensions of the patient's blood vessels. Sheath 512 carries, near
its distal end, a balloon 514 that is provided to assist guidance
of the sheath to bring the distal end to a point in the pulmonary
artery. As shown in FIG. 13, sheath 512 is constructed, similar to
a Swan-Ganz sheath, or catheter, to be capable of being inserted
through a vein in the arm or neck and to then be guided through the
superior vena cava, the right atrium, the tricuspid valve, the
right ventricle, and the pulmonary valve of the patient's
heart.
[0149] The embodiment further includes a wire 516 that will be
guided through sheath 512 and that carries, at its distal end, as
shown in FIG. 14, a filter composed of a framework 518 and a filter
mesh material 522 constructed as in the case of the embodiments
previously described, to allow the passage of blood, while blocking
the flow of debris. The filter further includes a plurality of wire
struts 530 secured, preferably in a sliding manner, as shown by
opening 534, to wire 516.
[0150] Struts 518 and 530 are preferably made of nitinol.
[0151] The filter is constructed, similar to the filters described
earlier herein, to have a radially compressed state and a radially
expanded state and to automatically assume the radially expanded
state when unconstrained.
[0152] In the embodiment shown in FIGS. 13 and 14, the filter will
be housed in sheath 512 until the distal end of sheath 512 reaches
a desired location in the pulmonary artery. Then, wire 516 will be
advanced while sheath 512 is held stationary, to cause the filter
to emerge from the distal end of sheath 512 and assume its radially
expanded state, as shown in FIG. 14. The filter is dimensioned to
extend entirely across the pulmonary artery in order to trap any
debris released during heart surgery and thus prevent debris from
entering the patient's lungs.
[0153] After the medical procedure has been completed and the flow
of debris has subsided, the appliance may be removed in one of the
following ways:
[0154] Wire 516 will be pulled back while sheath 512 is held
stationary to withdraw the filter into sheath 512, while the filter
is brought to its radially compressed state with the aid of struts
530, or sheath 512 will be advanced over the filter to place the
filter in its radially compressed state within sheath 512. Then,
sheath 512, with the filter held therein, is withdrawn from the
patient's body in the reverse direction along the insertion path;
or
[0155] A slit is made in the pulmonary artery to access the filter,
the filter is radially compressed and wire 515 is cut by suitable
instruments, after which the filter is withdrawn through the slit
in the artery. Then, sheath 512 and the remainder of wire 516 are
withdrawn in the reverse direction along the insertion path.
[0156] Sheath 512 may, for example, have a diameter of 10 Fr. The
proximal end of sheath 512 may be connected to a suction device 550
that helps to suction debris collected in the filter.
[0157] Suction device 550 may, in turn, be connected to an
arrangement such as components 410, 412 and 414, as shown in FIG.
12. Debris leaving filter 414 may pass through a Coulter counter to
monitor the presence of debris.
[0158] With respect to all embodiments of the invention, if a
filter having a larger compression ratio, e.g. 16:1, is used, the
filter sheath may have a correspondingly smaller diameter.
[0159] The presently disclosed embodiments are therefore to be
considered in all respects as illustrative and not restrictive, the
scope of the invention being indicated by the appended claims,
rather than the foregoing description, and all changes which come
within the meaning and range of equivalency of the claims are
therefore intended to be embraced therein.
* * * * *