U.S. patent application number 11/861954 was filed with the patent office on 2009-03-26 for braided vascular devices having no end clamps.
This patent application is currently assigned to AGA MEDICAL CORPORATION. Invention is credited to Daniel O. Adams, Paul Pignato.
Application Number | 20090082803 11/861954 |
Document ID | / |
Family ID | 40472532 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090082803 |
Kind Code |
A1 |
Adams; Daniel O. ; et
al. |
March 26, 2009 |
BRAIDED VASCULAR DEVICES HAVING NO END CLAMPS
Abstract
In some embodiments, a medical device may include one or more of
the following features: (a) a metal fabric formed of braided metal
strands, (b) the medical device having a collapsed configuration
for delivery through a channel in a patient's body and having a
generally dumbbell-shaped expanded configuration with two expanded
diameter portions separated by a reduced diameter portion formed
between opposed ends of the device and unsecured metal strand ends
at the opposed ends, and (d) a thrombogenic agent located on the
metal fabric.
Inventors: |
Adams; Daniel O.; (Long
Lake, MN) ; Pignato; Paul; (Stacy, MN) |
Correspondence
Address: |
AGA Medical Corporation
5050 Nathan Lane North
Plymouth
MN
55442-3209
US
|
Assignee: |
AGA MEDICAL CORPORATION
Plymouth
MN
|
Family ID: |
40472532 |
Appl. No.: |
11/861954 |
Filed: |
September 26, 2007 |
Current U.S.
Class: |
606/213 |
Current CPC
Class: |
A61B 2017/00575
20130101; A61B 17/12172 20130101; A61B 2017/00867 20130101; A61B
17/12109 20130101; A61B 2017/00615 20130101; A61B 2017/00623
20130101; A61B 17/0057 20130101; A61B 17/12022 20130101; A61B
17/12113 20130101; A61B 2017/12054 20130101; A61B 2017/12095
20130101; A61B 17/12177 20130101; A61B 17/12036 20130101 |
Class at
Publication: |
606/213 |
International
Class: |
A61B 17/03 20060101
A61B017/03 |
Claims
1. A collapsible medical device, comprising: at least one layer of
a plurality of metal strands woven into a tubular braided metal
fabric having a proximal end, a distal end, and a segment there
between; the tubular woven metal fabric having an expanded preset
configuration shaped for treatment of an opening in a body organ;
and the expanded preset configuration being deformable to a lesser
cross-sectional dimension for delivery through a channel in a
patient's body, the woven metal fabric having a memory property
whereby the medical device returns to the expanded preset
configuration when delivered into the patient's body, said proximal
and distal ends being free of clamps and having at least a portion
of the segment larger in diameter than the free wire ends in the
expanded preset configuration.
2. The collapsible medical device of claim 1, wherein the medical
device is an occluder.
3. The collapsible medical device of claim 1, wherein the medical
device is a shunt.
4. The collapsible medical device of claim 1, wherein the medical
device is a flow restrictor.
5. The collapsible medical device of claim 1, further comprising an
occluding fiber retained within an expandable hollow central
portion formed by said tubular woven fabric.
6. The collapsible medical device of claim 1, wherein the metal
fabric is manufactured from an alloy selected from the group
consisting of stainless steel, nickel-titanium, and
cobalt-chromium-nickel.
7. The collapsible medical device of claim 1, wherein the device
comprising the expanded preset configuration is the shape of a
disc.
8. A medical device comprising: a metal fabric formed of braided
metal strands; the medical device having a collapsed configuration
for delivery through a channel in a patient's body and having a
generally dumbbell-shaped expanded configuration with two expanded
diameter portions separated by a reduced diameter portion formed
between opposed ends of the device and unsecured metal strand ends
at the opposed ends.
9. The medical device of claim 8, wherein the medical device can be
any one of an occluder, shunt, or flow restrictor.
10. The medical device of claim 8, wherein the metal strand ends
are unsecured from metal clamps.
11. The medical device of claim 8, wherein the metal strand ends do
not unravel.
12. The medical device of claim 8, wherein the medical device is
delivered to a treatment site in a patient without physical
connection to a delivery device.
13. The medical device of claim 8, wherein the unsecured metal
strand ends do not extend outside of the expanded diameter
portions.
14. The medical device of claim 8, further comprising a
thrombogenic agent located on the metal fabric.
15. A method of forming a medical device, the method comprising the
steps of: providing a metal fabric formed of a plurality of braided
strands, the strands being formed of a metal which can be heat
treated to substantially set a desired shape; deforming the metal
fabric to generally conform to a wall surface of a moulding
element; heat treating the metal fabric in contact with the surface
of the moulding element at an elevated temperature, the temperature
and the duration of the heat treatment being sufficient to
substantially set the shape of the fabric in its deformed state;
removing the metal fabric from contact with the moulding element;
and cutting the fabric adjacent the device side of the clamps after
heat treatment.
16. The method of claim 15, further comprising the step of clamping
the opposite ends of the strands before deforming the metal
fabric.
17. The method of claim 15, further comprising the step of cutting
an appropriately sized piece of the metal fabric.
18. The method of claim 17, further comprising the step of forming
a long tubular braid from the metal fabric.
19. The method of claim 15, wherein the metal of which the strands
are formed is a shape memory alloy, stainless steel, or elgiloy,
the temperature and the duration of the heat treatment being
selected to substantially set the strands in a deformed state.
20. A method for delivering a self-expanding medical device to a
selected site in a vascular system comprising the steps of: (a)
selecting the combination of: (i) a delivery device inner catheter
having a lumen extending from a proximal end to a distal end, the
delivery device having an outer diameter adapted to slidingly fit
within the lumen of a delivery catheter, (ii) an elongate, flexible
member coaxially insertable through the lumen of the delivery
device catheter, said elongate flexible member having a plunger
member affixed thereto sized to at least partially fit within the
lumen of the delivery device catheter when a proximally directed
tension force is applied to the elongate flexible member with
respect to the delivery device catheter, (iii) a braided tubular
device having at least a portion of a segment larger in diameter
than free wire ends in the expanded preset configuration with the
free ends of individual strands comprising the device captured
between the plunger member and the delivery device catheter; (b)
feeding the delivery device catheter with the braided tubular
device attached through a lumen of the delivery catheter and out
thereof; and (c) moving the elongate flexible member relative to
the tubular delivery device catheter to release the tubular device
from the tubular delivery device catheter.
21. The method of claim 20, further comprising the step of
releasing a plunger spring located in the plunger member to capture
the free ends between the plunger member and the inner delivery
device catheter.
22. The method of claim 20, further comprising the step of
inserting the delivery catheter within a patient's vasculature.
23. The method of claim 20, further comprising the step of
repositioning the braided tubular device if it is not positioned
properly upon release from the tubular delivery device
catheter.
24. The method of claim 20, further comprising removing the
delivery device form the patient's vasculature.
25. The method of claim 20, further comprising removing the
delivery catheter from the patient's vasculature.
Description
FIELD OF THE INVENTION
[0001] Embodiments of the present invention generally relate to
intravascular devices for treating medical conditions.
Particularly, embodiments of the present invention relate to
intravascular devices for treating vascular conditions. More
particularly, embodiments of the present invention relate to
intravascular devices for selective occlusion of a vessel and/or
shunting or restricting flow in a vessel or organ within the body's
circulatory system.
BACKGROUND
[0002] A wide variety of intravascular devices are used in various
medical procedures. Certain intravascular devices, such as balloon
catheters, diagnostic catheters, stent delivery catheters, and
guidewires are generally used simply to deliver fluids or other
medical devices to specific locations within a patient's body, such
as a selective site within the vascular system. Other frequently
more complex, devices are used in treating specific conditions,
such as devices used in removing vascular occlusions or for
treating septal defects and the like.
[0003] In certain circumstances, it may be necessary to occlude a
patient's vessel, chamber, channel, hole, or cavity such as to stop
blood flow there through. In other cases it may be necessary to
create a flow restriction or to shunt flow from one vessel to
another to treat abnormal cardiovascular conditions. Examples of
selective occlusion are without limitation, closure of a Patent
Ductus Arteriosus (PDA), Atrial Septal Defect (ASD), Ventricular
Septal Defect (VSD), Patent Foreman Ovale (PFO), Arterial Venous
Fistula (AVF), or an Arterial Venous Malformation (AVM).
[0004] Mechanical embolization devices are well known in the art
and sold commercially for occlusion of vessels in various locations
within the vasculature. Intravascular occlusion devices can be
fabricated from Nitinol (NiTi) wire strands that have been braided
to form a tubular fabric which is then heat set in a mold to an
expanded shape, but which can be compressed for delivery through a
catheter to a treatment site whereby the device, when urged out of
the delivery catheter, self-expands within the vasculature to
occlude blood flow at the treatment site. The details of the
various designs and configurations as well as methods of
fabricating and using the devices are known in the art.
[0005] An example of a shunting procedure is shunting of blood
between the portal vein and the hepatic vein; know as a
Transjugular Intrahepatic Portosystemic Shunt (TIPS). Certain forms
of congenital disease may require a communication between the right
atrium and left atrium. Shunting may also be required for treating
specific abnormal conditions, such as bi-passing vascular
occlusions within an internal passageway.
[0006] Congenital heart defects are examples of the necessity for
flow restriction where holes in the septum allow blood to flow from
the high pressure left ventricle to the lower pressure right
ventricle causing excess blood flow to the lungs. The body's
natural reaction is to constrict the vessels to the lungs to
restrict blood flow. Over time, this causes a thickening of the
pulmonary arteries and ultimately leads to closure of smaller lung
arteries and further complications if left untreated. The treatment
involves early mechanical flow restriction of blood to the lungs
until a surgical fix can be accomplished.
[0007] The occluding, shunting, and flow restricting devices
described above use similar technology for fabrication. Each device
is formed from a plurality of resilient metal strands of a shape
memory alloy woven into a braided fabric to create a resilient
material which can be heat treated to substantially set a desired
shape. In performing the heat treatment step, the braided fabric is
first deformed to generally conform to a molding surface of a
molding element and the braided fabric is then heat treated in
contact with the surface of the molding element at an elevated
temperature. The time and temperature of the heat treatment is
selected to substantially set the braided fabric in its deformed
state. After the heat treatment, the fabric is removed from contact
with the molding element and will substantially retain its shape in
the deformed state. The braided fabric so treated defines an
expanded state of a medical device, but which can be longitudinally
stretched to reduce its cross-sectional profile so that it can be
deployed through a catheter into a channel in a patient's body. The
device connects to a delivery device by a threaded connection. Once
the delivery catheter's distal end with the device contained within
its lumen is placed at the treatment site, the device is urged out
of the delivery catheter and self-expands to its expanded preset
configuration. Once the device is positioned as desired, the
delivery device is unthreaded and the delivery catheter and
delivery device are removed from the body.
[0008] One limitation of these devices is the need to clamp the
ends of the wire strands at each end of the device to prevent
unraveling. In such untreated NiTi fabrics, the strands will tend
to return to their unbraided configuration and the braid can
unravel fairly quickly unless the ends of the length of braid that
has been cut to form the device, are constrained relative to one
another. One method which has proven to be useful to prevent the
braid from unraveling is to clamp the braid at two locations and
cut the braid to leave a length of the braid having clamps at
either end, thereby effectively defining an empty space within a
sealed length of fabric. These clamps will hold the ends of the cut
braid together and prevent the braid from unraveling.
[0009] Alternatively, one can solder, braze, weld or otherwise
affix the ends of the desired length together (e.g., with a
biocompatible cementitious organic material) before cutting the
braid. Although soldering and brazing of NiTi alloys have proven to
be fairly difficult, the ends can be welded together, such as by
spot welding with a laser welder.
[0010] Devices marketed using these technologies include the
braided metal clamps to prevent unraveling of the metal strands.
The clamps add to the diameter of the collapsed device for delivery
through a catheter as well as project outward from some
configurations of the device. These outward projections are often
in the blood flow path and could be a source of clot formation or
result in flow disruption.
[0011] Some have provided a recess in each end surface of the
device where each braided end of the device is held together with a
clamp. The clamps are recessed into the expanded diameter portion
of the device, thereby reducing the overall length dimension of the
device and creating a low profile occluder. However, the recessed
clamps cause the fabric to reverse direction in the heat-set state.
In the compressed state, the wires are higher stressed and exert an
increased outward drag against the wall of the delivery catheter
making it more difficult to push the device through the
catheter.
[0012] In the case of a flow restrictor or shunt device, the
braided wire end clamps make the device configuration bulky and
un-necessarily complex, since the natural placement of the clamps
is in a co-axial position to the braided tube, which ideally, is
where the flow path should be. The designs described require extra
manufacturing steps to create the flow path. In addition the
manufacturing cost of the device is higher than need be if the
clamps were not used.
[0013] With reference to FIGS. 1A-C, 2, 3, and 4, prior occluders,
shunts, and flow restrictors are shown respectively. FIGS. 1A-C
illustrate an occluder design that may he described as having a
flanged or disc shape at each end, connected by a smaller diameter
portion between them. FIGS. 2 & 3 are two views of a shunt
device. FIG. 4 is an example of a flow restrictor.
[0014] FIG. 1A shows the design of an occluder 10 having enlarged
diameter discs or flanges 11 & 12 at each end and a small
connecting diameter between the ends. Each end of the device has a
wire end clamp. The distal clamp 14 and proximal clamp 13 hold the
wire ends from unraveling. The side view FIG. 1B illustrates how
clamps 13 extend from the end of the device. Clamp 13 contains
internal threads 15 that mate with external threads 16 on delivery
device 17 as depicted in FIG. 1C. A polyester fabric disc 18 is
used to improve device thrombogenicity and is sutured into disc 12.
The fabric collapses with the device for delivery through a
delivery catheter.
[0015] It would be desirable for a medical device to achieve
occlusion, flow restriction, or shunting of blood in the human
vasculature that is:
[0016] of a lower collapsed deliverable profile;
[0017] deliverable through a delivery catheter with less force;
[0018] less intensive to manufacture;
[0019] less disruptive to blood flow; and
[0020] can be manufactured at a reduced cost.
SUMMARY OF THE INVENTION
[0021] In some embodiments, a collapsible medical device may
include one or more of the following features: (a) at least one
layer of a plurality of metal strands woven into a tubular braided
metal fabric having a proximal end, a distal end, and a segment
there between, (b) the tubular woven metal fabric having an
expanded preset configuration shaped for treatment of an opening in
a body organ, (c) the expanded preset configuration being
deformable to a lesser cross-sectional dimension for delivery
through a channel in a patient's body, the woven metal fabric
having a memory property whereby the medical device returns to the
expanded preset configuration when delivered into the patient's
body, said proximal and distal ends being free of clamps and having
at least a portion of the segment larger in diameter than the free
wire ends in the expanded preset configuration, and (d) an
occluding fiber retained within an expandable hollow central
portion formed by said tubular woven fabric.
[0022] In some embodiments, a medical device may include one or
more of the following features: (a) a metal fabric formed of
braided metal strands, (b) the medical device having a collapsed
configuration for delivery through a channel in a patient's body
and having a generally dumbbell-shaped expanded configuration with
two expanded diameter portions separated by a reduced diameter
portion formed between opposed ends of the device and unsecured
metal strand ends at the opposed ends, and (d) a thrombogenic agent
located on the metal fabric.
[0023] In some embodiments, a method of forming a medical device
may include one or more of the following steps: (a) providing a
metal fabric formed of a plurality of braided strands, the strands
being foaled of a metal which can be heat treated to substantially
set a desired shape, (b) deforming the metal fabric to generally
conform to a wall surface of a moulding element, (c) heat treating
the metal fabric in contact with the surface of the moulding
element at an elevated temperature, the temperature and the
duration of the heat treatment being sufficient to substantially
set the shape of the fabric in its deformed state, (d) removing the
metal fabric from contact with the moulding element, (e) cutting
the fabric adjacent the device side of the clamps after heat
treatment, (f) clamping the opposite ends of the strands before
deforming the metal fabric, (g) cutting an appropriately sized
piece of the metal fabric, and (h) forming a long tubular braid
from the metal fabric.
[0024] In some embodiments, a method for delivering a
self-expanding medical device to a selected site in a vascular
system may include one or more of the following steps: (a)
selecting the combination of: (i) a delivery device inner catheter
having a lumen extending from a proximal end to a distal end, the
delivery device having an outer diameter adapted to slidingly fit
within the lumen of a delivery catheter, (ii) an elongate, flexible
member coaxially insertable through the lumen of the delivery
device catheter, said elongate flexible member having a plunger
member affixed thereto sized to at least partially fit within the
lumen of the delivery device catheter when a proximally directed
tension force is applied to the elongate flexible member with
respect to the delivery device catheter, (iii) a braided tubular
device with free ends of individual strands comprising the device
captured between the plunger member and the delivery device
catheter, (b) feeding the delivery device catheter with the braided
tubular device attached through a lumen of the delivery catheter
and out thereof, (c) moving the elongate flexible member relative
to the tubular delivery device catheter to release the tubular
device from the tubular delivery device catheter, (d) releasing a
plunger spring located in the plunger member to capture the free
ends between the plunger member and the inner delivery device
catheter, (e) inserting the delivery catheter within a patient's
vasculature, (f) repositioning the braided tubular device if it is
not positioned properly upon release from the tubular delivery
device catheter, (g) removing the delivery device from the
patient's vasculature, (h) removing the delivery catheter from the
patient's vasculature.
DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1A shows a perspective view of a prior art
occluder.
[0026] FIG. 1B shows a side view of the occluder design of FIG.
1A.
[0027] FIG. 1C shows an enlarged view of a clamp used in the
occluder of FIG. 1A along with a delivery device threaded end.
[0028] FIG. 2 shows a side view of a prior art shunt device having
an eccentric lumen and two discs with recessed securement
connectors.
[0029] FIG. 3 shows a top view of a shunt device of FIG. 2 having
an eccentric linen and two discs with recessed securement
connectors.
[0030] FIG. 4 shows a perspective view of a prior art flow
restrictor.
[0031] FIG. 5A shows a perspective view of an occluder without end
clamps in an embodiment of the present invention.
[0032] FIG. 5B shows a side view of an occluder without end clamps
in an embodiment of the present invention.
[0033] FIG. 5C shows an enlarged wire end view of an occluder
without end clamps.
[0034] FIG. 5D shows a delivery device in an embodiment of the
present invention.
[0035] FIG. 6 shows a flowchart diagram of a method of
manufacturing a medical device in accordance with embodiments of
the present invention.
[0036] FIG. 7A shows a partial side cross-sectional view of a prior
art occluder illustrating the clamp and clamp recess only one end
of the device.
[0037] FIG. 7B shows a frontal end view of the occluder of FIG. 7A
illustrating the clamp and clamp recess on one end of the
device.
[0038] FIG. 7C shows a partial side cross-sectional of an occluder
without end clamps in an embodiment of the present invention.
[0039] FIG. 7D shows a frontal end view of an occluder without end
clamps in an embodiment of the present invention.
[0040] FIG. 8A shows a cross-sectional view of a design for either
a flow restrictor or a shunt in an embodiment of the present
invention.
[0041] FIG. 8B shows a frontal end view of a design for either a
flow restrictor or a shunt in an embodiment of the present
invention.
[0042] FIG. 9 shows a side view of another occluder embodiment of
the present invention.
[0043] FIG. 10 shows a side view of an occluder shown occluding an
aneurysm in an embodiment of the present invention.
[0044] FIG. 11 shows a flow chart diagram of a method of
implantation of a medical device in accordance with embodiments of
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0045] The following discussion is presented to enable a person
skilled in the art to make and use the present teachings. Various
modifications to the illustrated embodiments will be readily
apparent to those skilled in the art, and the generic principles
herein may be applied to other embodiments and applications without
departing from the present teachings. Thus, the present teachings
are not intended to be limited to embodiments shown, but are to be
accorded the widest scope consistent with the principles and
features disclosed herein. The following detailed description is to
be read with reference to the figures, in which like elements in
different figures have like reference numerals. The figures, which
are not necessarily to scale, depict selected embodiments and are
not intended to limit the scope of the present teachings. Skilled
artisans will recognize the examples provided herein have many
useful alternatives and fall within the scope of the present
teachings. It's understood that the embodiments of the present
teachings can be applied to occluders, shunts, or flow
restrictors.
[0046] Embodiments of the present invention can be well suited for
the selective occlusion, shunting, or flow restriction of a vessel
lumen, channel, cavity, or organ within the body's circulatory
system. Embodiments of the present invention disclose a vascular
occlusion, flow restriction, or shunt device formed of a plurality
of wire strands woven into a braided tubular metal fabric having an
expanded preset configuration and an elongated collapsed reduced
diameter configuration. The device can be delivered through a
catheter to a treatment site and shaped to create an occlusion,
flow restriction, or shunt, when placed in an opening in a body
organ or vessel. The woven metal fabric can have a memory property
whereby the medical device tends to return to an expanded preset
configuration when unconstrained. The device can have proximal and
distal unsecured wire ends and a segment there between the wire
ends having at least a portion of the segment larger in diameter
than the unsecured wire ends in the expanded preset
configuration.
[0047] Embodiments of the present invention can be fabricated from
many various methods including those described in U.S. Pat. No.
6,123,715, titled Method of forming medical devices; intravascular
occlusion devices, to Amplatz herein incorporated by reference in
its entirety. Additionally, while it could be helpful to
temporarily clamp or otherwise fix the wire ends during the wire
cutting operation and during heat treatment to set the desired
device shape, the inventors have discovered that the clamps are not
needed after the heat treatment process since the heat treatment
imparts a wire shape memory that resists unraveling of the braid
wire ends. The elimination of the clamps reduces the device profile
by elimination of the material of the clamps which surrounded the
wires. In addition the wire ends may be positioned in an end wall
of the device and need not be oriented outward from the device in
an axial orientation as in prior devices. The recessing of the
device end surfaces to hide the clamps is not required since the
wire ends can be incorporated into the plane of the end surfaces of
the device which simplifies the fabrication process and reduces
manufacturing cost. Since the recessing of the device end surfaces
is not required, the fabric reverse bends near the clamp are not
required and the delivery forces are reduced during passage through
the delivery catheter.
[0048] In the case of shunt devices or a flow restrictor such
fabrication methods can be used such as those described in U.S.
Pat. No. 6,468,303, titled "Retrievable Self Expanding Shunt", by
Amplatz et. al. and U.S. Pat. No. 6,638,257, titled "Intravascular
Flow Restrictor", by Amplatz et. al. herein incorporated by
reference in their entirety. In shunts and flow restrictors the
elimination of the wire end clamps allow the axial area of the
device ends to be available as a flow passage, simplifying the
device design and lowering the device profile and manufacturing
cost.
[0049] In the prior art solutions described herein, at least one of
the wire end clamps served as a means to connect a delivery device.
This was accomplished by providing internal (female) threads in at
least one clamp that mated with external (male) threads on the
delivery device. However, embodiments of the present invention
disclose that the clamps are no longer necessary and therefore a
new delivery system is disclosed below in more detail. The new
delivery system includes an outer tubular guide catheter, an inner
tubular delivery (pusher) catheter coaxially disposed and slidable
relative to the outer guide catheter. An elongated flexible guide
wire or cable that is coaxially insertable, through thee lumen of
the inner tubular catheter that has a frusto-conical bead affixed
at the distal end thereof sized to at least partially fit within
the lumen of the inner pusher catheter when a proximally directed
tension force is applied between the elongated flexible wire or
cable with respect to the pusher catheter. By inserting a
compressed coiled spring between a proximal end portion of the
cable, the requisite clamping force is maintained to secure the
device proximal wire ends to the distal end of the pusher catheter
until the compression spring force is removed. Such a delivery
system and improvements there to are described by Pending Patent
Application U.S. Patent Publication No. 2006/0253184, titled
"System for the Controlled Delivery of Stents and Grafts", by
Amplatz et al. and by U.S. Patent Publication No. 2007/0118207,
titled "System for Controlled Delivery of Stents and Grafts", by
Amplatz et al. herein incorporated by reference in its
entirety.
[0050] In one embodiment of the invention, a simplified medical
device and a method of fabrication of a medical device, without the
limitations inherent to having wire end clamps, for treating
vascular or organ abnormalities which necessitate occlusion, flow
restriction or shunting as the method of treatment is disclosed. In
another embodiment of the present invention, a method of treating a
medical condition requiring the occlusion, flow restriction, or
shunting of blood flow in a vessel or cavity within the body's
vasculature using a simplified medical device fabricated from a
resilient braided metal fabric having a preset expanded
configuration and a collapsed configuration for delivery through
the vasculature using a novel delivery system is disclosed.
[0051] These and other features and advantages of the inventive
design will become readily apparent to those skilled in the art
from a review of the drawings and the detailed description of the
preferred embodiment in conjunction with the accompanying claims
and drawings.
[0052] With reference to FIGS. 5A-B, perspective views of an
occluder without end clamps is shown. Embodiments of the present
invention disclose an occluder 100 that can be formed of a
plurality of wire strands 102 woven into a braided metal fabric 104
having an expanded preset configuration as shown by discs 112 and
114 and an elongated collapsed reduced diameter configuration 115
for delivery through a catheter sleeve 120 to a treatment site
(FIG. 5). The device can also be shaped to create a flow restrictor
or shunt when placed in an opening in a body organ or vessel as
discussed above in detail. Woven metal fabric 104 can have a memory
property whereby occluder 100 tends to return to an expanded preset
configuration when unconstrained (e.g., by catheter sleeve 120).
Occluder 100 can have proximal and distal unsecured wire ends 106
and 108 and a segment 109 there between, having at least a portion
of the segment larger in diameter than the unsecured wire ends in
the expanded preset configuration.
[0053] Metal strands 102 define two sets of essentially parallel
generally helical strands, with the strands of one set having a
"hand" (e.g., a direction of rotation, opposite that of the other
set). This is a generally tubular fabric 104, known in the fabric
industry as a tubular braid. The pitch of wire strands 102 (e.g.,
the angle defined between the turns of the wire and the axis of the
braid) and the pick of fabric 104 (e.g. the number of wire
crossovers per unit length) may be adjusted as desired for a
particular application. Wire strands 102 of metal fabric 104 used
can be formed of a, material which is both resilient and which can
be heat treated to substantially set a desired shape. Materials
which are suitable for this purpose include a cobalt-based low
thermal expansion alloy referred to in the field as Elgeloy,
nickel-based high temperature-high-strength "superalloys"
commercially available from Haynes International located in Kokomo,
Ind. under the trade name Hastelloy, nickel-based heat treatable
alloys sold under the name Incoloy by International Nickel located
in Toronto, Canada, and a number of different grades of stainless
steel. A factor in choosing a suitable material for wires 102 is
that they retain a suitable amount of the deformation induced by
the molding surface when subjected to a predetermined heat
treatment.
[0054] One class of materials which meet these qualifications are
so-called shape memory alloys. One particularly preferred shape
memory alloy for use in the present method is a Nitinol alloy that
is very elastic this alloy is said to be "superelastic" or
"pseudoelastic". This elasticity will help a device return to a
preset expanded configuration for deployment.
[0055] With reference to FIG. 6, a flowchart diagram of a method of
manufacturing a medical device in accordance with embodiments of
the present invention is shown. Manufacturing process 200 begins at
state 204 where a large piece of fabric 104 which is formed, for
example, by braiding wire strands 102 to form a long tubular braid.
At state 206, ends 106 and 108 can be secured. One can clamp, tape,
solder, braze, weld or otherwise affix ends 106 and 108 to the
desired length (e.g., length greater than final device length)
together (e.g., with a biocompatible cementitious organic material)
before cutting the braid. At state 208, an appropriately sized
piece of metal fabric 104 is cut from the larger piece of fabric
104 by cutting outside the clamps, leaving the clamps to contain
the braid ends of the device segment. Metal sleeves clamped or
swaged onto the braid are a preferred clamp design and can be
easily removed after heat treatment by cutting the fabric adjacent
the clamps. Since the clamps contain braided heat set filaments set
in the axial direction, the braid should be cut to place the wire
ends in the plane of the device ends. Compressing the heat set
shape or elongating the braid by pulling on the clamps allows the
braid to be placed into a small diameter sleeve for holding
purposes during the braid cutting process. A laser or mechanical
cutter as well known in the art may be used to cut the braid.
Mechanical cutting may require deburring of sharp wire cut
ends.
[0056] Using a temporary clamp is helpful as it can be removed
easily after heat treatment. Permanent wire end bonds would need to
be cut off after heat treatment. Tape can also hold the ends from
unraveling during handling but will not survive the heat treatment;
however, at this point in the process minor unraveling is not a
factor since the final device braided fabric length will be
shortened by cutting.
[0057] Once an appropriately sized piece of metal fabric 104 is
obtained, fabric 104 is deformed at state 210 to generally conform
to a surface of a molding element. Deforming the fabric will
re-orient the relative positions of the strands of the metal fabric
from their initial order to a second, re-oriented configuration.
The shape of the molding element should be selected to deform the
fabric into substantially the expanded shape of the desired
component of the medical device.
[0058] Once the molding element is assembled with metal fabric 104
generally conforming to a molding surface of that element, fabric
104 can be subjected to a heat treatment at state 212 while it
remains in contact with that molding surface. Suitable heat
treatments of Nitinol wire to set a desired shape are well known in
the art. It has been found that holding a Nitinol fabric at about
500.degree. C. to about 550.degree. C. for a period of about 1-30
minutes, depending on the softness or harness of the device to be
made, will tend to set fabric 104 in its deformed state, e.g.
(wherein it conforms to the molding surface of the molding
element). At lower temperatures the heat treatment time will tend
to be greater (e.g., about one hour at about 350.degree. C.) and at
higher temperatures the time will tend to be shorter (e.g., about
30 seconds at about 900 degrees C.). After the heat treatment and
cooling, fabric 104 is removed from contact with the molding
element at state 214 and will substantially retain the molded
shape.
[0059] At step 216, the fabric adjacent the device side of the
clamps is cut after heat treatment. Thus cutting the fabric
adjacent the clamps inherently removes the clamps. Any temporary
wire clamps or other means of holding the wire ends, if used, are
thus removed at state 216 after the heat treatment process by
cutting the braided wire adjacent the clamps as previously
explained to provide a desired final device length at state
218.
[0060] With reference again to FIGS. 5A-C all occluder without end
clamps is shown. It is noted there are no clamps for wire ends 106
and 108. Discs 112 and 114, after heat treatment and removal from
the mold, can be axially elongated by compressing them such that
occluder 100 elongates and can be advanced into a cut to length
fixture. The excess length from each end can be trimmed by manually
cutting or using a laser to cut wires 102 to length. As illustrated
in FIG. 5B, the cut length can be such that wire ends 106 and 108
are positioned near device central axis 110. Alternatively, wire
ends 106 and 108 could be cut shorter resulting in wire ends 106
and 108 positioned into a larger diameter. The result is occluder
100 is shorter in length compared to know prior art devices and
there are no clamps. As is known in the art, a polyester fabric
disc 113 can be used to improve device thrombogenicity and can be
sutured into disc 114. For an occluder device the fabric disk 114
could have no central passage as opposed to the case for a flow
restrictor or shunt device where a central flow passage in fabric
disk 114 if used, could be fabricated to allow for controlled blood
passage.
[0061] FIG. 5D shows wire ends 106 pushed into a delivery catheter
sleeve 120. Delivery system 129 includes an outer tubular guide
catheter 124, an inner tubular deliver (pusher) catheter 121
coaxially disposed and slidable relative to outer guide catheter
124. The delivery system comprises an elongated flexible guide wire
122 or cable that is coaxially insertable through lumen 131 of the
inner tubular catheter 121 and that has a frusto-conical bead 123
affixed at the distal end thereof sized to at least partially fit
within lumen 131 of the inner pusher catheter 121 when a proximally
directed tension force is applied between the elongated flexible
wire or cable with respect to pusher catheter 121. By inserting a
compressed coiled spring between a proximal end portion of cable
122 and a fixed hub on pusher catheter 121, the requisite clamping
force is maintained to secure occluder 100 proximal wire ends 106
to the distal end of pusher catheter 121 until the compression
spring force is removed. A frusto-conical plunger 123 moves axially
with the shaft 122 to clamp the inside of wire ends 106 or 108
against the inside surface of sleeve 120. Sleeve 120 is attached to
the distal end of pusher catheter 121. Plunger 123 is spring loaded
to clamp device wire ends 106 or 108 but can be released by
advancement of shaft 122 to release occluder 100 when properly
positioned in a body. With ends 106 or 108 clamped within sleeve
120, occluder 100 may be drawn proximally into a delivery catheter
124 coaxially arranged over pusher catheter 121. Once deliver
catheter 124 is advanced within the vasculature adjacent the site
of treatment, the delivery device may be advanced or catheter 124
withdrawn to allow occluder 100 to freely self expand to its
pre-determined memorized shape. Once occluder 100 is in place,
occluder 100 is released by advancing frusto-conical clamping
mechanism 123 relative to sleeve 120. With occluder 100 fully
deployed the delivery system 129 is removed from the body, leaving
occluder 100 implanted at the treatment site.
[0062] In the embodiment shown in FIGS. 1A-C, polyester fabric 18
provides an occluding surface across device 10 and therefore the
choice of location for cutting the wire ends is not that critical.
Wire ends 106 could he cut and lie anywhere in outer discs 112 and
114 but preferably are near central axis 110 to provide a double
wall to discs 112 and 114.
[0063] With reference to FIG. 7A, a partial side cross-sectional
view and end view of a prior art occluder portion illustrating the
clamp and clamp recess on one end of the device is shown. The
device of FIG. 7A illustrates device designs whereby the surface
containing the end clamp is recessed to make, the device shorter.
In FIG. 7A, a cross-sectional view is provided of a recessed end 30
and wire end clamp 31 of a prior art device.
[0064] With reference to FIG. 7C, a partial side cross-sectional
and end view of an occluder without end clamps in an embodiment of
the present invention is shown. Recess 132 is eliminated in the
design and wire ends 134 are cut after heat treatment such that
wire ends 134 terminate near device central axis 135. Occluder 130
may have an optional polyester disc 112 or 114 sutured in for
improved occlusion.
[0065] With reference to FIG. 8, a side and end view respectively
of a design for either a flow restrictor or a shunt in an
embodiment of the present invention is shown. Braided device 140
has two raised flanges 141 and 142 which locate against the vessel
surface to retain device 140. Flanges 141 and 142 are sized to be
somewhat larger (e.g., 10-30%) than the vessel inside diameter to
produce an outward force against the vessel wall to anchor device
140 and prevent dislodgement. An optional polyester fabric 143 is
sutured 144 across raised flange 142 diameter. Fabric 143 has a
hole 145 in the central portion, sized to create a flow limiting
area as desired for the restriction of blood flow or shunting of
blood through a vessel or across a membrane. In the case of
shunting blood flow through a membrane, raised flanges 141 and 142
would be more disc-like in shape and the discs would be separated
by the thickness of the membrane with one disc on either side of
the membrane and loaded against the membrane. In either design, the
clamps in the prior art devices are replaced by un-bound cut wire
ends 146 which are positioned to lie in device end surface 148. It
is of note, that there are no clamps, recesses, or holes being
forced through a braided fabric where the wires need to be manually
rearranged and spaced evenly as in the prior art devices. This
reduces manufacturing cost and provides a lower profile device that
is easier to deliver.
[0066] With reference to FIG. 9, a side view of another occluder
embodiment of the present invention is shown. A PDA occluder is
illustrated in a side view of bell shaped occluder 150. There are
no clamps in device 150 and wire ends 151 are cut so as to be
positioned near the central axis of the device's tapered distal
end. Proximal device wire ends 152 are cut to length such as to lie
in a recessed surface within flange 154. Optionally, wire ends 152
could be cut to a longer length to end near the proximal device
central axis. A polyester fabric 153 is optionally sutured across
the diameter of the device distal flange 154 to improve
thrombogenicity (reduce the time to occlusion).
[0067] With reference to FIG. 10, aside view of an occluder shown
occluding an aneurysm in an embodiment of the present invention is
illustrated. Occluder 300 could eliminate a distal recess and
distal clamp and cut wire ends 299 to a length such that they are
positioned near the distal axis of the device. The proximal clamp
would be eliminated and proximal wire ends 298 cut to a length to
position the ends in the flange outer surface facing the inside of
the vessel. This improved design has minimal projection into the
flow stream and thus the risk of a clot forming and breaking off
from a clamp an entering the blood stream is diminished.
[0068] Further, it is anticipated that an occluder, stent, or flow
restrictor could take any shape and could be offered for new
applications or different anatomical conditions. In addition it is
contemplated that a device may be fabricated using multiple metal
fabric layers. The individual layer wire ends could be cut to the
same length or have staggered cut ends. The multiple layers could
increase the metal content of the device and cause quicker
occluding times, thus eliminating the need for polyester or other
fabric to improve throbogenicity. The multiple layers could he
sutured together in a central area and generally at least one layer
could be a primary structural layer while one or more layers could
be of lesser radial strength and generally of smaller wire diameter
and smaller pore size between filaments. The braided pitch of each
layer could generally be the same to allow uniform expansion and
contractions. The layers may have the same or different shapes to
fill a hollow space within the outer layer. A multi-layered device
may in addition include an occluding fiber within the hollow
portion of the device or one or more layers may be coated with a
drug to promote clotting or if desired with a drug such as heparin
to inhibit thrombus formation, depending on the application.
[0069] Those skilled in the art will appreciate that in order to
speed up the occlusion of the vessel; the device may be coated with
a suitable thrombogenic agent, filled with a polyester fiber or
braided with an increased number of wire strands. This fiber easily
collapses with the device for delivery through a catheter. This
fiber is also useful for occlusion devices, although use of
multiple-layers of braided fabric may function in a similar manner
to the polyester fabric to speed thrombosis. The interwoven fiber
by attachment to clot retains the clot firmly within the device as
it forms the occlusion.
[0070] The tubular braid used to fabricate occlusion devices for
example, in embodiments of the present invention may range from
wire having a diameter of 0.002 to 0.005 inch, possibly in the
range of 0.003 to 0.0035 inch and for a PDA device possibly 0.003
inch diameter. The number of wires in the tubular braid may vary
from 36 to 144 but it is most helpful if it is in the range of 72
to 144 and for a PDA device is preferably 144 wires. The pick count
of the braid may vary from 30 to 100 and preferably from 50 to 80
and for a PDA device is preferably 70.
[0071] With reference to FIG. 11, a flow chart diagram of a method
of implantation of a medical device in accordance with embodiments
of the present invention is shown. A part of a method of
implantation 301, once access has been obtained to a vessel, an
introducer catheter is inserted into the vessel and maintains a
position from outside the body to within a vessel such as the
femoral artery at state 302. Access to the patient's vessel of
treatment is obtained using the Seldinger Technique as is commonly
known in the art. Delivery catheter 124 can be placed into
vasculature and navigated to the treatment site such that the
distal end of catheter 124 is adjacent the treatment site at state
304. A clinician could select a medical device suitable for the
condition being treated at state 306. The device could be furnished
separately or could be pre-loaded onto a delivery device as is
illustrated in FIG. 5D. If furnished separately, a device could be
in a reduced diameter sleeve with the proximal device wire ends
exposed for loading into the delivery device. A delivery catheter
could be selected based on the particular device and anatomical
conditions. The delivery device could be first placed through the
lumen of the delivery catheter until the distal end is adjacent the
distal end of the catheter at step 308.
[0072] With reference again to FIG. 5D, occluder 100 having
proximal wire ends 106 and 108 could be inserted over plunger 123
into delivery device sleeve 120 at state 308 while the spring
loaded frusto-conical plunger 123 is advanced distally with respect
to sleeve 120 to open sleeve access 126. Once wire ends 106 or 108
are inserted into sleeve 120, plunger spring 123 can be released to
move plunger 123 proximally toward wire ends 106 or 108 at state
310. Spring pressure locks wire ends 106 or 108 between sleeve 120
and the plunger surface. Delivery device 121 and occluder 100 may
now be drawn together proximally to draw occluder 100 into lumen
127 of delivery catheter 124 adjacent the distal end at state 312.
Since occluder 100 can be formed from Nitinol and can have shape
memory, this reduction in diameter does not harm occluder 100.
[0073] Delivery catheter 124 can be slowly pulled proximal while
holding back on delivery device 121 to allow the distal end of
occluder 100 to emerge from delivery catheter 124 and to self
expand to its pre-determined shape at state 314. If occluder 100 is
not positioned as desired occluder 100 may be returned to delivery
catheter 124 by either advancement of delivery device 121 while
holding delivery catheter 124 stationary or holding delivery
catheter stationary 124 and pulling proximally on delivery device
121 at state 316. In the case of flanged or double disk devices
where one disk is placed on either side of a septum, delivery
catheter 124 distal end is placed distal to the septum and then
withdrawn partially relative to the delivery device 121 to allow
the distal disk only to self expand. The delivery catheter 124 and
delivery device 121 are now pulled proximally together to locate
the first expanded disk against the septum. The delivery catheters
124 is now withdrawn proximally while holding the delivery device
121 in place to allow the second disk to self expand on the
proximal side of the septum. Assuming occluder 100 is positioned as
desired, fully deployed plunger 123 may be displaced distally
relative to sleeve 120 to release occluder 100. Delivery catheter
124 and delivery device 121 can next be removed from the body
leaving occluder 100 implanted in the vessel, cavity, or treatment
site at state 318.
[0074] In an alternative method of treatment delivery catheter 124
may first be placed into the desired treatment site using a
technique of advancement over a steerable guide wire as well know
in the interventional medical art. Occluder 100 may be connected to
delivery device 121 as previously stated and occluder 100 and
delivery device 121 advanced into the proximal end of delivery
catheter 124 using a tear-away introducer tapered to pilot into
delivery catheter 124 and coaxially placed over the delivery device
121 distal end. Once occluder 100 is within catheter 124 the
tear-away introducer is removed and occluder 100 advanced adjacent
the distal end of delivery catheter 124. In all other aspects,
occluder 100 placement is as previously described. Delivery
catheter 124 may be a guide catheter or steerable sheath in other
embodiments.
[0075] In another embodiment of the delivery device disclosed in
patent application US 2007/0118207A1, the delivery system 129
replaces wire or cable 122 (FIG. 5D) with a hollow tube suitable
for passage of a guidewire there through. In such cases where the
guide catheter 124 is introduced into the vasculature over a
guidewire prior to device selection, the delivery, catheter may be
advanced over the guidewire within the guide catheter. In all other
aspects the procedure is similar.
[0076] Thus, embodiments of the BRAIDED VASCULAR DEVICES HAVING NO
END CLAMPS are disclosed. One skilled in the art will appreciate
that the present teachings can be practiced with embodiments other
than those disclosed. The disclosed embodiments are presented for
purposes of illustration and not limitation, and the present
teachings are limited only by the claims that follow.
* * * * *