U.S. patent application number 12/583744 was filed with the patent office on 2011-03-03 for device and method for occluding the left atrial appendage.
Invention is credited to John Bridgeman, Christopher Clark, Gregg Sutton.
Application Number | 20110054515 12/583744 |
Document ID | / |
Family ID | 43625970 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110054515 |
Kind Code |
A1 |
Bridgeman; John ; et
al. |
March 3, 2011 |
Device and method for occluding the left atrial appendage
Abstract
An implantable medical device for insertion in the left atrial
appendage includes a cap coupled to a frame. The cap constrains
movement of the legs of the frame during collapse and expansion of
the device, such that the device can be deployed, recalled and
redeployed without the device being damaged or the legs of the
frame getting tangled.
Inventors: |
Bridgeman; John;
(Minneapolis, MN) ; Sutton; Gregg; (Maple Grove,
MN) ; Clark; Christopher; (St. Michael, MN) |
Family ID: |
43625970 |
Appl. No.: |
12/583744 |
Filed: |
August 25, 2009 |
Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61B 2017/00601
20130101; A61B 17/0057 20130101; A61B 17/12172 20130101; A61B
17/12122 20130101; A61B 2017/00632 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61M 29/02 20060101
A61M029/02 |
Claims
1. An implantable medical device for insertion in a left atrial
appendage of a patient comprising: a frame; a cap connected to said
frame; a membrane coupled to and covering a portion of said
frame.
2. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 1 wherein: said frame
includes limbs terminating in a frame joint element; said cap
including spokes emanating from a cap center hub and terminating in
a cap joint element; said frame joint element coupled to said cap
joint element.
3. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 1 wherein each said limb
is coupled to one spoke.
4. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 2, wherein one of said
joint elements is a male-shaped member and said mating joint
element is a female-shaped member.
5. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 4 wherein one of said
joint members is an elongate tang and the other of said joint
members is an aperture defined by said spoke that is sized and
shaped to receive said tang.
6. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 2 wherein: said cap joint
element is an elongate tang; said frame joint element is an
aperture in said limb; said hinges formed by the insertion of said
elongate tang into said aperture.
7. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 6 wherein said device
defines an interior space and wherein said spoke tangs pass through
said limb slots from the exterior of the device to the interior
space.
8. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 6 wherein said tang has a
flange adjacent its terminating end, said flange being sized such
that it slides through said mating joint element aperture when in a
first orientation thereto, but is prohibited from sliding through
said aperture when in another orientation with respect thereto.
9. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 8, wherein said aperture
is a rectangular slot having a width that is smaller than the
largest dimension of said flange has a largest dimension and said
slot having a length that is longer than the largest dimension of
said flange.
10. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 2 wherein: the device has
a longitudinal axis and is deformable between a deployed
configuration in which said spokes extend generally radially
outward from said axis and a second undeployed configuration in
which said spokes extend generally parallel to and are concentric
with said axis and in which said cap is substantially enclosed
within said frame in said undeployed configuration.
11. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 10 wherein: said spokes
are hingedly coupled to said center hub.
12. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 2 wherein: said spokes of
said distal cap are continuous with said cap center and wherein
said coupling of said spokes to said hub is achieved through
flexing of said spokes with respect to said hub.
13. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 12, wherein said distal
cap has a tissue-driving region and a tissue-following region.
14. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 11 wherein an anterior
direction extends along the longitudinal axis of the device from
its proximal end towards its distal end and wherein the terminating
ends of said limbs lie in an anterior plane and wherein a portion
of said distal cap extends, in the anterior direction, beyond said
anterior plane forming a bumper and wherein said distal cap bumper
portion is atraumatic at the implant site.
15. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 14 wherein said bumper
portion of said distal cap lies at the radial edge of the
device.
16. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 14, wherein each said
spoke includes a curved portion between said center hub and its
terminating end and wherein said curved portion has a radius of
curvature that lies within the interior of a volume defined by the
device.
17. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 10, wherein the
terminating ends of said limbs lie in an anterior plane and wherein
said hub lies posterior to said anterior plane when said device is
in its deployed configuration and when it is in its undeployed
configuration
18. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 1: said frame includes
retention members.
19. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 18 wherein each retention
member has a barb adjacent a distended ridge of the frame.
20. An implantable medical device for insertion in a left atrial
appendage of a patient according to claim 19 wherein said distended
ridge limits the penetration depth of said hook into tissue.
21. A method of implanting a medical device for insertion in a left
atrial appendage comprising the steps of: a) providing an
implantable medical device having a frame with retension members
extending radially outwardly from said device, a cap connected to
said frame and a membrane coupled to and covering a portion of said
frame; b) collapsing said device within a delivery catheter; c)
implanting said device by deploying said device from said catheter,
said device expanding to its natural state, with retention members
engaging adjacent tissue; d) after implanting said device,
retracting said device into said catheter; and e) after retracting
the device, re-implanting the device by redeploying said device
from said catheter, said device expanding to its natural state,
with retention members engaging adjacent tissue.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Ser. No.
10/351,736, filed Jun. 24, 2003 which in turn claims the benefit of
U.S. provisional application No. 60/351,898, filed Jan. 25, 2002,
U.S. provisional application No. 60/379,921, filed May 10, 2002,
U.S. provisional application No. 60/417,110, filed Oct. 8, 2002 and
U.S. provisional application No. 60/403,720, filed Aug. 14, 2002,
all of which are hereby incorporated by reference in their
entireties herein.
FIELD OF THE INVENTION
[0002] An implantable medical device and method for occluding the
left atrial appendage of a patient is disclosed.
BACKGROUND OF THE INVENTION
[0003] Implanted medical devices are available for insertion into
the left atrial appendage (LAA). Such devices are used, for
example, to block blood clots from passing out of the heart into
the systemic circulation.
[0004] In general these devices are delivered to the LAA through a
catheter system that enters the venous circulation and approaches
the left atrium through the atrial septum between the right and
left side of the heart. The catheter is guided through the septum
toward the ostium of the left atrial appendage. After acquisition
and insertion into the LAA the implanted medical device is
deployed, and fixed so that it remains in the appendage. Once
positioned, the implanted medical device is released by the
catheter, and the catheter system is removed. Over time, the
exposed surface structures of the implanted medical device spanning
the ostium of the LAA becomes covered with tissue. This process is
called endothelization.
SUMMARY OF THE INVENTION
[0005] There is a continuing need to improve these occlusion type
implanted medical devices as well as the methods and catheter
devices used to deliver them into the LAA. The preferred version of
the device of the present invention is preferably formed as two
separate metal pieces. In practice a membrane-covered frame and a
complimentary cap are linked or coupled together with a linkage. In
one embodiment the linkage is a hinge mechanism. The assembled
device has an expanded, deployed configuration and a collapsed,
compressed configuration. It is biased into the expanded or
deployed configuration by the superelastic nature of the frame
material and processing. In the deployed configuration, the device,
and more specifically, the membrane of the device, spans the ostium
of the left atrial appendage. In the compressed configuration, the
device fits within a delivery catheter for transport and delivery
to the LAA. When the device is compressed within a delivery
catheter, the cap folds inward and is carried within the interior
of the frame.
[0006] The cap serves to regulate or control the deployment process
and protects the attachment structures or retention members
associated with the periphery of the device. The preferred
retention structure is a series of barbs. These barbs penetrate
tissue and retain the device in the interior of the left atrial
appendage during implantation. The depth of the penetration is
controlled or managed by a structural feature on the frame, while
the retraction and recapture is managed by the cap which controls
the barbs during recapture, when the device is withdrawn into the
delivery catheter. This allows for redeployment and returns the
barbs to their original functionality.
[0007] In general the occlusion membrane is attached to the frame
by hooks or sutures. In one exemplary embodiment, the hooks are
formed as a unitary piece of the frame, thereby simplifying the
manufacture of the implanted medical device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Through he several figures of the drawing identical
reference numerals indicate identical structures wherein:
[0009] FIG. 1A is a side view of the implanted medical device
(IMD);
[0010] FIG. 1B is a perspective view of the IMD as seen from the
distal end;
[0011] FIG. 1C is a perspective view of the IMD as seen from the
proximal end;
[0012] FIG. 2 is a side view of the frame and cap separated;
[0013] FIG. 3A is an end view of the distal end of the frame;
[0014] FIG. 3B is a side view of the frame in isolation;
[0015] FIG. 4 is a side view of the cap in isolation;
[0016] FIG. 5 is a plan view of a hinge portion of the frame;
[0017] FIG. 6 is a plan view of a hinge portion of the cap;
[0018] FIG. 7 is a figure showing assembly of the cap and
frame;
[0019] FIG. 8 is a perspective view of the cap to frame hinge
connection;
[0020] FIG. 9 is a perspective view of the IMD near the tip of the
delivery catheter;
[0021] FIG. 10 is a perspective view of the IMD partially within a
delivery catheter;
[0022] FIG. 11 is a perspective view of the IMD with the retention
barbs emerging from the delivery catheter;
[0023] FIG. 12 is a perspective view of the IMD with the cap fully
deployed from the delivery catheter;
[0024] FIG. 13 is a perspective view of the entire IMD deployed
from the delivery catheter;
[0025] FIG. 14A is a section of the IMD showing the interaction of
the barb and the catheter lumen;
[0026] FIG. 14B is a section of the IMD showing the interaction of
the barb and the catheter lumen;
[0027] FIG. 14C is a section of the IMD showing the interaction of
the barb and the catheter lumen;
[0028] FIG. 14D is a section of the IMD showing the interaction of
the barb and the catheter lumen;
[0029] FIG. 15 is an enlarged view of portion of the IMD with one
of its barbs engaging surround tissue; and
[0030] FIG. 16 is a side view of the IMD shown in situ.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT(S)
[0031] FIGS. 1a, 1b and 1c show an exemplary embodiment of an
implantable medical device 1 for use occluding the Left Atrial
Appendage (LAA) of a patient's heart.
[0032] This device is deformable between an expanded, deployed
configuration, as depicted in FIGS. 1a, 1b and 1c, and a collapsed
configuration presented in FIG. 9.
[0033] In its expanded, deployed configuration, it is suitably
sized and shaped to lodge in the LAA, as depicted in FIG. 16.
[0034] In its collapsed configuration, the device is suitably sized
and shaped to pass through an intravascular delivery device. It is
depicted in its collapsed form and is shown in the deployment
process in FIGS. 9-13.
[0035] The device 1 has a proximal end 5 and an opposite distal end
6 and a longitudinal axis 7. The terms "proximal" and "distal" are
used herein for purposes of describing the orientation of device
elements and features with respect to one another; the terms are
not intended to be limiting. "Proximal" shall correspond to the
left portion of the device, as depicted as it is oriented in FIG.
1a, and "distal" shall correspond to the right portion of the
device.
[0036] Similarly, the terms "posterior" and "anterior" are used
herein for purposes of describing the orientation of device
elements and features with respect to one another; the terms are
not intended to be limiting. "Posterior" shall correspond to the
left portion of the device, as depicted in FIG. 1a, and "anterior"
shall correspond to the right portion of the device.
[0037] The "proximal direction" is depicted by arrow 8 in FIG. 1a
and is parallel to the longitudinal axis 7 and points toward the
proximal end 5; the "distal direction" is depicted by arrow 9 in
FIG. 1a and is parallel to the longitudinal axis 7 and points
toward the distal end 6.
[0038] Turning to FIG. 1a, the device is seen in its expanded form
showing the frame 10 connected to the cap 15 through hinge
structures. A membrane 19 is attached to and covers a portion of,
the frame 1. A series of barbs typified by barb 47 serve to secure
the device in the LAA. The cap 15 intersects with the frame to
manage the deployment and recapture of the frame 10 and the barbs
47. Without the cap, the limbs or ribs would tend to unfold at
random and interfere with each other. With the cap 15, the
deployment of each limb or rib is controlled and regularized so
that the limbs cannot get tangled and crossed with respect to one
another. The cap 15 does not appreciably extend beyond the length
L2 of the frame 10.
[0039] Turing to FIG. 1b the device is seen from the distal end in
perspective.
[0040] Turning to FIG. 1c the device is seen from the proximal end
in perspective. In situ, the membrane 19 completely covers the
surface exposed to the interior of the heart chamber. A posterior
connector 300 is threaded to releaseably couple the device to
deployment catheters.
[0041] FIG. 2 depicts the device in an assembly view. The exemplary
embodiment of device 1 has a proximal frame 10 and a distal cap 15.
The device 1 generally defines an interior space or volume 18. The
membrane 19 is connected to and supported by frame 10. This
membrane 19 is of a material providing the desired permeability for
an intended use. The membrane 19 can be a filter member that blocks
the passage of blood clots, but is permeable to blood flow there
through. Alternatively, this member 19 can be of a material
impermeable to blood flow. The membrane 19 may be fabricated from
any suitable biocompatible materials. These materials include, but
are not limited to, for example, ePFTE (e.g. Gortex.RTM.),
polyester (e.g. Dacron.RTM.), PTFE (e.g. Teflon.RTM.), silicone,
urethane, metal fibers, and other biocompatible polymers.
[0042] The frame 10 has the general shape of a cylinder with one
proximal closed end 20 and one distal open end 21 with cylindrical
sides 23 there between; in other words, the frame 10 is generally
cup-shaped with a terminating open end 21. Yet another way of
describing the shape of frame 10 is that it is U-shaped in
longitudinal cross-section (i.e. taken through the longitudinal
axis 7). The frame 10 has a length L2 in its natural or deployed
configuration. The frame 10 is generally circular or annular in
horizontal cross-section (i.e. taken perpendicular to the axis 7)
and has a diameter D1 in its deployed configuration. In one
exemplary embodiment, the aspect ratio between the full length of
the device 1 L1 and D1 is approximately 0.5 to 1:5. Due to the
flexibility and deformability of frame 10, its dimensions and shape
adjust somewhat to suit its deployed environment. More
specifically, the proximal end can force the tissues of the LAA
into a nearly circular shape to facilitate sealing; i.e. it
"drives" tissue. The next portion of the device length gently
conforms to the individual structure of the LAA and it effectively
follows the LAA shape, i.e. it "follows" the physiology rather than
"drives" it.
[0043] The membrane 19 covers the closed end 20 of the frame 10 and
extends along the sides 23 of the cylindrical wire frame 10. When
the device is in position within an LAA, the membrane 19 spans the
ostium and intercepts clots or mediates blood flowing in and out of
the LAA The membrane 19 can be attached to the frame 10 with
stitching or hooks or tangs or stakes.
[0044] An exemplary embodiment of the frame 10 or lattice is
further illustrated in FIGS. 3a and 3b without the membrane
attached. In the embodiment depicted, the device 1 has a unitary
construction and is formed from a single elastic metal mesh tube,
such as nitinol, that is selectively laser-cut into cells and is
then expanded and/or heat shaped and heat treated to create the
complex shape depicted in the figure. The frame 10 can be deformed,
under the compressive force of a catheter in a manner that will be
described in greater detail below with respect to FIGS. 9-13. The
frame 10 is suitably shaped so that its cylindrical side walls
engage vessel wall tissue to roughly fill the LAA. The frame 10 has
a number of roughly S-shaped wire portions, a representative one of
which is indicated by reference number 30, that serve as resilient
springs to expand the wire frame 10 to its natural or unconstrained
size and shape. The S-shaped wire portions emanate from a collar 35
where they are joined to one another or are continuous with one
another. The S-shaped curvature of wire portions 30 cause collar 35
to be geometrically recessed relative to a back, or posterior,
plane 37 of the wire frame 10.
[0045] The opposite distal ends of the frame 10 terminate in limbs,
a representative one of which is indicated by reference number 40.
Adjacent the terminating ends of limbs 40 are frame joint elements,
a representative one of which is indicated by reference number 45.
Frame joint elements 45 are hingedly coupled to mating joint
elements of cap 15, as will be discussed below with reference to
FIGS. 5-8.
[0046] The frame 10 includes tissue retention members or barbs 47
located about the periphery of the frame 10. In the exemplary
embodiment illustrated, these retention members 47 are barbs that
terminate outside of the interior volume 18 defined by the frame 10
and cap 15. The barbs 47, when extended, extend radially outward
farther than the adjacent portions of the frame 10. The barbs are
oriented to catch tissue to aid in retaining the device 1 in the
desired position within an LAA. More specifically, the barbs are
oriented to inhibit longitudinal movement of the device 1 in the
posterior direction 8.
[0047] The barbs 47 are adjacent a distended ridge 48 on the frame
10. The distended ridge 48 is a region of the frame 10 that extends
radially outward further than the adjacent area of the frame 10.
The distended ridge 48 aids in limiting the degree to which the
barbs penetrate the tissue to the distance indicated by dimension
49. This is illustrated in FIG. 15.
[0048] FIG. 4 shows an exemplary embodiment of a distal cap 15.
Distal cap 15 has a central hub 50 from which emanates a number of
spokes, a representative one of which is indicated with reference
number 55, each having first and second opposite ends 58, 59, where
the first ends 58 are connected to the hub 50, and the second ends
59 are terminating ends. The cap 15 is generally symmetrical about
longitudinal axis 52. A plane 51 is perpendicular to axis 52 and
passes through the posterior-most point of cap 15. In the
embodiment illustrated, the cap 15 is a unitary member; that is,
the spokes 55 are unitary with or contiguous with the hub 50. The
spokes have a natural or spring-biased position, as depicted, in
which the spokes are disposed at an angle 53 of between about 0 and
45 degrees with respect to the plane 51. Its complementary angle
54, between the cap's axis 52 and the spokes 50 is, correspondingly
between about 90 and 45 degrees.
[0049] Between ends 58 and 59, each spoke 55 includes a curved
portion 60 that has a radius of curvature 70 that is on the
interior of the volume 18 and is circumscribed by the frame and cap
when they're assembled as shown in FIG. 1a. The curvature of the
curved portion 60 yields an angle 75 of between about 0 and 90
degrees between the terminating end 59 of the spoke and an elongate
portion 80 of the spoke that lies between the hub and the curved
portion 60.
[0050] The terminating end 59 of the spoke 55 provides a cap joint
element 90 that couples with a mating frame joint element 45 on
frame 10, as will be described below in greater detail with respect
to FIGS. 6-9.
[0051] The cap 15 is spring-biased to the shape illustrated in FIG.
4. It can be folded, upon application of force, such that the
spokes 15 move toward parallel with the axis 52. More specifically,
the spokes 55 are hingedly coupled to the hub 50 and are foldable
with respect thereto.
[0052] The cap 15 is formed of biocompatible materials that provide
a spring-biased connection of the spokes to the hub. For example,
the cap 15 can be formed of an elastic metal mesh, such as nitinol,
cut and heat-shaped to yield the natural, spring-biased
configuration shown in FIG. 4.
[0053] Additional aspects of the geometry of cap 15 will be
appreciated with reference to FIG. 1a. When coupled to the frame
10, the hub 50 of cap 15 is inwardly recessed. In other words, an
anterior plane 100 is defined by terminating ends 41 of the limbs
40. This plane is the distal-most part of frame 10. When the cap 15
is coupled to the frame 10, the hub 50 lies posterior to the
anterior plane 100. This is the hub's orientation in both the
natural, deployed, expanded configuration shown in FIG. 1a, as well
as in its compressed configuration for transport within a catheter,
as will be described below with reference to FIGS. 9-13. Still
another way of expressing this relationship is to note that in both
the compressed configuration and the natural configuration, the hub
lies between the anterior plane 100 and the posterior plane 37. Yet
another way of expressing this relationship is to note that the
hub, in the compressed configuration, is substantially enclosed
within the frame 10. When the device 1 is compressed, the hub 50
moves relative to the frame 10 in the proximal direction.
[0054] As further illustrated in the embodiment of FIG. 1a, when
the frame 10 and cap 15 are assembled, each terminating end 41 of
the frame 10 is coupled to one spoke 55 of the cap. The
longitudinal axis 52 of the cap is colinear with the axis 7 of the
frame 10.
[0055] The cap 15 performs multiple functions in the device 1.
During deployment the cap provides relatively uniform forces on the
terminating ends 41 of the limbs 40 so that during deformation
between compressed and deployed configurations, and vice versa, the
frame 10 is held relatively concentrically about the axis 7. By
constraining the ends of the limbs the cap prevents them from
becoming entangled and this is an aid to the consistent,
predictable and efficient deployment and redeployment of the
device. The controlled motion of the limbs during deployment and
recapture prevents the barbs from hooking onto companion limbs and
breaking or folding or becoming otherwise tangled in the limbs. In
use, where several redeployments may be required to achieve proper
positioning, this means that fewer devices per procedure are
required, thereby reducing the costs associated with the
procedure.
[0056] Another function of the cap 15 is to provide an atraumatic
contact surface at the anterior of the device as it is deployed
from a catheter and maneuvered into position. The curved portions
60 of the cap 15 form a bumper portion 125 as will be appreciated
from FIG. 1a. This bumper portion 125 extends anteriorly beyond the
anterior plane 100 of the frame 10, such that the curved portions
60 would make first contact with tissue. More specifically, the
bumper portion 125 extends a distance L1 minus L2 beyond the plane
100.
[0057] Turning to FIGS. 5-8, the hinged coupling between the frame
10 and the cap 15 is accomplished through mating joint elements,
one male and one female. In the embodiment illustrated and
described here, the male element resides on the cap 15 and the
female on the frame 10; this configuration however might be
swapped. As depicted in FIG. 5, the female joint element 150 is an
aperture 155. In the embodiment depicted, the aperture 155 is
rectangular and has a width X1 and a length Y1.
[0058] As depicted in FIG. 6, the male joint element 160 is a tang
165 at the terminating end 59 of the spoke 55. The tang 165
includes a neck 170 having a width W3. The neck 170 extends between
a flange 180 and a shoulder 185. The neck 170 is narrower than the
flange and shoulder. More specifically, shoulder 185 has a width
W2, neck 170 has a width of W3 and flange 180 has a width of W4,
where W3 is less than W2 and W4.
[0059] Male joint element 160, FIG. 6, is sized and shaped to be
received by female joint element 150, FIG. 5, and to be held in
place. Specifically, Y1 is large enough to accommodate W4; however
X1 is smaller than W4. X1 is large enough to accommodate W3. W2 is
larger than X1 and Y1. Hence, as depicted in FIG. 7, the cap 15 is
coupled to the frame 10 by twisting the spoke 55 somewhat to orient
the tang 65 parallel to the length of the aperture 155. The tang
165 is then passed through the aperture 155. When the flange 180 of
the tang 165 has cleared the aperture and is let "loose" it springs
roughly 90 degrees to its natural orientation, such that the flange
180 and shoulder 185 abut the limb 40 in the area adjacent and
defining the aperture 155, thereby holding the spoke 55 against
displacement relative to the limb 40, as depicted in FIG. 8.
[0060] Although the interlocking structure shown is preferred in
this generation of device it is possible to connect the elements
with laser welds or the like.
[0061] To deploy the device 1 in an LAA, the device 1 is tethered
to a deployment wire, such as by a screw connection to a posterior
connector 300. The device is compressed within a catheter that is
then percutaneously coursed through the blood vessel to the desired
location. When the end of the catheter is adjacent the desired
location, the device is deployed, expanding toward its natural size
and shape, as depicted in FIGS. 9-13. FIG. 9 shows the device 1 as
it emerges, cap 15 or bumper portion 125 first, from the catheter
400. FIGS. 10-12 show the frame 10 and its cap 15 expanding toward
its natural, expanded form, as depicted in FIG. 13. When the device
1 is properly positioned and fully deployed, it is untethered or
released from the deployment wire.
[0062] As best seen from FIG. 12, the cap 15 radially expands and
serves to guide the opening of the radial limbs 40 of the frame 10.
The limbs 40 are approximately equally spaced from each other at
least in part because of the forces exerted by the cap on the ends
41 of the limbs 40, pulling each limb 40 approximately uniformly
radially outward. This action is desirable since it prevents the
barbs typified by barb 47 from entangling with other frame cells or
structures.
[0063] FIGS. 14a-d show the intersection between a constrained barb
47 and the open lumen 401 defined by the delivery catheter 400.
During retrieval of the device 1 back into the catheter 400, the
ridge 48 and the barb 47 cooperate to fold the barb 47 down so that
it can reenter the deployment catheter 49. The wall of the catheter
400 is sufficiently stiff relative to the barb 47 to force the barb
47 to flex into the lumen 401 as seen in the sequence of figures
FIGS. 14a-d. The barbs illustrated in FIGS. 14a-d are prevented
from rotating into the lumen 401 because the ridge 48 and cell are
constrained from rotation by the cap 15 (not shown).
[0064] The illustrative embodiment of the device is shown as a
two-piece construction. In one embodiment, the linkages between the
frame and cap are hinged. In general, the two-piece construction
allows for the required mechanical properties to be met with a
minimum of complexity and processing. However it should be apparent
that the same structure can be achieved with a single piece device.
It should also be observed that the two-piece construction allows
the device to easily achieve a partitioning of functionality along
the length of the device. As noted above, the proximal end can
force the tissues of the LAA into a nearly circular shape to
facilitate sealing; i.e. it "drives" tissue. The next portion of
the device length gently conforms to the individual structure of
the LAA and it effectively follows the LAA shape, i.e. it "follows"
the physiology rather than "drives" it. The final most distal
section of the device with the cap is very compliant and is very
blunt so that the device can accommodate the LAA without
unnecessary trauma.
[0065] As described, the structural features of the device allow
for it to be deployed and redeployed without tangling or damage to
the device or its retention members. Thus, the device provides for
installation of the device according to a method having the
following steps:
a) providing an implantable medical device having a frame having
retention members extending radially outwardly from said device, a
cap connected to said frame and a membrane coupled to and covering
a portion of said frame; b) collapsing the device within a delivery
catheter; c) implanting the device by deploying the device from
said catheter, with the device expanding to its natural state, with
retention members engaging adjacent tissue; d) after implanting the
device, retracting the device into the catheter; and e) after
retracting the device, re-implanting the device by redeploying it
from the catheter, with the device expanding to its natural state,
with retention members engaging adjacent tissue.
* * * * *