U.S. patent application number 13/660875 was filed with the patent office on 2013-02-28 for device and method for replacing mitral valve.
This patent application is currently assigned to EDWARDS LIFESCIENCES CORPORATION. The applicant listed for this patent is Edwards Lifesciences Corporation. Invention is credited to Mark Chau, Son V. Nguyen, Stanton J. Rowe.
Application Number | 20130053950 13/660875 |
Document ID | / |
Family ID | 40897344 |
Filed Date | 2013-02-28 |
United States Patent
Application |
20130053950 |
Kind Code |
A1 |
Rowe; Stanton J. ; et
al. |
February 28, 2013 |
DEVICE AND METHOD FOR REPLACING MITRAL VALVE
Abstract
A prosthetic mitral valve assembly is disclosed. The assembly
comprises a radially-expandable stent including a lower portion
sized for deployment between leaflets of a native mitral valve and
an upper portion having a flared end. The upper portion is sized
for deployment within the annulus of the mitral valve and the
flared end is configured to extend above the annulus. The stent is
formed with a substantially D-shape cross-section for conforming to
the native mitral valve. The D-shape cross-section includes a
substantially straight portion for extending along an anterior side
of the native mitral valve and a substantially curved portion for
extending along a posterior side of the native mitral valve. The
assembly further includes a valve portion formed of pericardial
tissue and mounted within an interior portion of the stent for
occluding blood flow in one direction.
Inventors: |
Rowe; Stanton J.; (Newport
Coast, CA) ; Chau; Mark; (Aliso Viejo, CA) ;
Nguyen; Son V.; (Irvine, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Edwards Lifesciences Corporation; |
Irvine |
CA |
US |
|
|
Assignee: |
EDWARDS LIFESCIENCES
CORPORATION
Irvine
CA
|
Family ID: |
40897344 |
Appl. No.: |
13/660875 |
Filed: |
October 25, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12113418 |
May 1, 2008 |
|
|
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13660875 |
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Current U.S.
Class: |
623/2.19 |
Current CPC
Class: |
A61B 2017/0417 20130101;
A61F 2230/0078 20130101; A61B 17/0401 20130101; A61F 2/2427
20130101; A61F 2/90 20130101; A61B 2017/00243 20130101; A61F
2210/0014 20130101; A61F 2/2418 20130101; A61F 2230/0067 20130101;
A61F 2220/0008 20130101; A61F 2220/0016 20130101; A61F 2230/0054
20130101; A61L 2430/20 20130101; A61F 2/2436 20130101; A61L 27/50
20130101; A61B 2017/0496 20130101; A61F 2/2457 20130101; A61F
2250/0039 20130101; A61L 27/3625 20130101; A61F 2/2454
20130101 |
Class at
Publication: |
623/2.19 |
International
Class: |
A61F 2/24 20060101
A61F002/24 |
Claims
1. A prosthetic mitral valve assembly, comprising: a
radially-expandable stent including a lower portion sized to held
between leaflets of a native mitral valve and an upper portion
having a flared end, the upper portion sized for deployment within
the annulus of the mitral valve with a pressure fit, the flared end
configured to extend above the annulus, wherein the stent tapers
from the upper portion to the lower portion, the stent having a
substantially D-shape cross-section for conforming to the native
mitral valve, the D-shape cross-section providing a substantially
straight portion configured to extend along an anterior side of the
native mitral valve and a substantially curved portion configured
to extend along a posterior side of the native mitral valve; and a
valve portion formed of pericardial tissue and mounted within an
interior portion of the stent, the valve portion having leaflets
for occluding blood flow in one direction and replacing the
function of the native mitral valve.
2. The prosthetic mitral valve assembly of claim 1, wherein the
stent is made of nitinol.
3. The prosthetic mitral valve assembly of claim 1, wherein the
valve portion comprises three leaflets.
4. The prosthetic mitral valve assembly of claim 1, wherein the
valve portion is a bicuspid valve having only two leaflets.
5. The prosthetic mitral valve assembly of claim 4, wherein the two
leaflets differ in size.
6. The prosthetic mitral valve assembly of claim 1, wherein the
stent is formed with intercrossing bars.
7. The prosthetic mitral valve assembly of claim 1, further
including tension members extending between the leaflets and the
stent.
8. The prosthetic mitral valve assembly of claim 7, wherein the
tension members are coupled at different heights, relative to one
another, along a length of the stent.
9. The prosthetic mitral valve assembly of claim 1, wherein the
stent has a truncated conical shape.
10. The prosthetic mitral valve assembly of claim 1, wherein the
flared end is scalloped.
11. The prosthetic mitral valve assembly of claim 1, wherein the
prosthetic mitral valve assembly is held in place without clamping
onto tissue.
12. The prosthetic mitral valve assembly of claim 1, wherein the
stent includes external prongs to assist in holding the prosthetic
mitral valve assembly in place.
13. The prosthetic mitral valve assembly of claim 1, wherein the
stent and the valve portion are collapsible to a reduced diameter
for insertion into the heart on a delivery catheter for
implantation.
14. The prosthetic mitral valve assembly of claim 1, further
including a tether coupled to the stent on one end thereof, the
tether being configured to couple the stent to a portion of the
heart remote from the stent.
15. The prosthetic mitral valve assembly of claim 1, wherein the
valve portion further includes tension members coupled to the
prosthetic leaflets for preventing the prosthetic leaflets from
everting and reducing stresses induced by ventricular
contraction.
16. The prosthetic mitral valve assembly of claim 15, wherein the
tension members are coupled to the prosthetic leaflets at a first
end of the tension members and coupled at an opposite end to the
stent or to a patient's heart.
17. The prosthetic mitral valve assembly of claim 15, wherein the
tension members are coupled to the stent at a first end of the
tension members and coupled at an opposite end to a portion of the
patient's heart.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/113,418, filed May 1, 2008, the disclosure of which is
incorporated by reference.
FIELD
[0002] The present disclosure concerns a prosthetic mitral heart
valve and a method for implanting such a heart valve.
BACKGROUND
[0003] Prosthetic cardiac valves have been used for many years to
treat cardiac valvular disorders. The native heart valves (such as
the aortic, pulmonary and mitral valves) serve critical functions
in assuring the forward flow of an adequate supply of blood through
the cardiovascular system. These heart valves can be rendered less
effective by congenital, inflammatory or infectious conditions.
Such damage to the valves can result in serious cardiovascular
compromise or death. For many years the definitive treatment for
such disorders was the surgical repair or replacement of the valve
during open heart surgery, but such surgeries are prone to many
complications. More recently a transvascular technique has been
developed for introducing and implanting a prosthetic heart valve
using a flexible catheter in a manner that is less invasive than
open heart surgery.
[0004] In this technique, a prosthetic valve is mounted in a
crimped state on the end portion of a flexible catheter and
advanced through a blood vessel of the patient until the valve
reaches the implantation site. The valve at the catheter tip is
then expanded to its functional size at the site of the defective
native valve such as by inflating a balloon on which the valve is
mounted.
[0005] Another known technique for implanting a prosthetic aortic
valve is a transapical approach where a small incision is made in
the chest wall of a patient and the catheter is advanced through
the apex (i.e., bottom tip) of the heart. Transapical techniques
are disclosed in U.S. Patent Application Publication No.
2007/0112422, which is hereby incorporated by reference Like the
transvascular approach, the transapical approach includes a balloon
catheter having a steering mechanism for delivering a
balloon-expandable prosthetic heart valve through an introducer to
the aortic annulus. The balloon catheter includes a deflecting
segment just proximal to the distal balloon to facilitate
positioning of the prosthetic heart valve in the proper orientation
within the aortic annulus.
[0006] The above techniques and others have provided numerous
options for high-risk patients with aortic valve stenosis to avoid
the consequences of open heart surgery and cardiopulmonary bypass.
While procedures for the aortic valve are well-developed, such
procedures are not necessarily applicable to the mitral valve.
[0007] Mitral valve repair has increased in popularity due to its
high success rates, and clinical improvements noted after repair.
However, a significant percentage (i.e., about 33%) of patients
still receive open-heart surgical mitral valve replacements due to
calcium, stenosis, or anatomical limitations. There are a number of
technologies aimed at making mitral repair a less invasive
procedure. These technologies range from iterations of the Alfieri
stitch procedure to coronary sinus-based modifications of mitral
anatomy to subvalvular placations or ventricular remodeling
devices, which would incidently correct mitral regurgitation.
[0008] However, for mitral valve replacement, few less-invasive
options are available. There are approximately 60,000 mitral valve
replacements (MVR) each year and it is estimated that another
60,000 patients should receive MVR, but are denied the surgical
procedure due to risks associated with the patient's age or other
factors. One potential option for a less invasive mitral valve
replacement is disclosed in U.S. Patent Application 2007/0016286 to
Herrmann. However, the stent disclosed in that application has a
claw structure for attaching the prosthetic valve to the heart.
Such a claw structure could have stability issues and limit
consistent placement of a transcatheter mitral replacement
valve.
[0009] Accordingly, further options are needed for less-invasive
mitral valve replacement.
SUMMARY
[0010] A prosthetic mitral valve assembly and method of inserting
the same is disclosed.
[0011] In certain disclosed embodiments, the prosthetic mitral
valve assembly has a flared upper end and a tapered portion to fit
the contours of the native mitral valve. The prosthetic mitral
valve assembly can include a stent or outer support frame with a
valve mounted therein. The assembly is adapted to expand radially
outwardly and into contact with the native tissue to create a
pressure fit. With the mitral valve assembly properly positioned,
it will replace the function of the native valve.
[0012] In other embodiments, the mitral valve assembly can be
inserted above or below an annulus of the native mitral valve. When
positioned below the annulus, the mitral valve assembly is sized to
press into the native tissue such that the annulus itself can
restrict the assembly from moving in an upward direction towards
the left atrium. The mitral valve assembly is also positioned so
that the native leaflets of the mitral valve are held in the open
position.
[0013] In still other embodiments, when positioned above the
annulus, prongs or other attachment mechanisms on an outer surface
of the stent may be used to resist upward movement of the mitral
valve assembly. Alternatively (or in addition), a tether or other
anchoring member can be attached to the stent at one end and
secured to a portion of the heart at another end in order to
prevent movement of the mitral valve assembly after implantation. A
tether may also be used to decrease the stress on the leaflets of
the replacement valve and/or to re-shape the left ventricle.
[0014] In still other embodiments, the prosthetic mitral valve
assembly can be inserted using a transapical procedure wherein an
incision is made in the chest of a patient and in the apex of the
heart. The mitral valve assembly is mounted in a compressed state
on the distal end of a delivery catheter, which is inserted through
the apex and into the heart. Once inside the heart, the valve
assembly can be expanded to its functional size and positioned at
the desired location within the native valve. In certain
embodiments, the valve assembly can be self-expanding so that it
can expand to its functional size inside the heart when advanced
from the distal end of a delivery sheath. In other embodiments, the
valve assembly can be mounted in a compressed state on a balloon of
the delivery catheter and is expandable by inflation of the
balloon.
[0015] These features and others of the described embodiments will
be more readily apparent from the following detailed description,
which proceeds with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a perspective view of a stent used in certain
embodiments of a mitral valve assembly.
[0017] FIGS. 2A and 2B are a perspective views an embodiment of a
mitral valve assembly using the stent of FIG. 1, as viewed from the
top and bottom, respectively, of the assembly.
[0018] FIG. 3 is a cross-sectional view of a heart with the mitral
valve assembly of FIG. 2 implanted within the native mitral
valve.
[0019] FIG. 4 is an enlarged cross-sectional view of a heart with
an embodiment of the mitral valve assembly implanted below an
annulus of the native mitral valve.
[0020] FIG. 5 is an enlarged cross-sectional view of a heart with
an embodiment of the mitral valve assembly implanted within the
native mitral valve wherein a tether is attached to the stent for
preventing migration of the mitral valve assembly.
[0021] FIG. 6 is a perspective view of a mitral valve assembly
having external anchoring members to assist in securing the mitral
valve assembly to the surrounding tissue.
[0022] FIG. 7 is a perspective view of an embodiment of a stent
having a scalloped end portion.
[0023] FIGS. 8A-8D are cross-sectional views showing an embodiment
of the mitral valve assembly inserted using a transapical
procedure.
[0024] FIG. 9 is a perspective view of an embodiment of a
prosthetic valve assembly having tensioning members coupled to
prosthetic leaflets of the valve to simulate chordae tendinae.
[0025] FIG. 10 is a perspective view of a prosthetic valve assembly
having tensioning members, according to another embodiment.
[0026] FIG. 11 is a perspective view of a prosthetic valve assembly
having tensioning members, according to another embodiment.
[0027] FIG. 12 is a perspective view of a prosthetic valve assembly
having a bicuspid valve, according to another embodiment.
[0028] FIG. 13 is a top view of the prosthetic valve assembly of
FIG. 12 with the bicuspid valve in a closed or at-rest
position.
[0029] FIG. 14 is a top view of the prosthetic valve assembly of
FIG. 12 with the bicuspid valve in an open position.
[0030] FIG. 15 is a perspective view of a prosthetic valve assembly
having tensioning members coupled to a bicuspid valve in a closed
position, according to another embodiment.
[0031] FIG. 16 is a perspective view of the prosthetic valve
assembly of FIG. 15 with the bicuspid valve in an open
position.
[0032] FIG. 17 is a cross-sectional view of a prosthetic valve
assembly having a non-uniform cross-sectional shape.
DETAILED DESCRIPTION
[0033] As used herein, the singular forms "a," "an," and "the"
refer to one or more than one, unless the context clearly dictates
otherwise.
[0034] As used herein, the term "includes" means "comprises." For
example, a device that includes or comprises A and B contains A and
B but can optionally contain C or other components other than A and
B. A device that includes or comprises A or B may contain A or B or
A and B, and optionally one or more other components such as C.
[0035] FIG. 1 is a perspective view of a stent 10 configured for
placement in a native mitral valve. The stent in this embodiment
includes an upper portion 12 having an enlarged or flared end 14
that tapers to a lower portion 16 having a reduced diameter. The
stent generally has a bell shape or a truncated conical shape, but
other shapes can be used. The stent 10 can have a continuous taper
from the flared end 14 to the lower end 15. As described below, at
least the upper portion desirably tapers in a direction from the
upper end to the lower end 15 so as to generally conform to the
contours of the native leaflets to assist in securing the stent
within the native valve. In some embodiments, the portion of the
stent extending below the native leaflets can have a generally
cylindrical shape or could further taper. Additionally, the length
of the stent 10 can vary. In some embodiments the stent can be
between 15-50 mm in length. For example, specific testing has been
performed on stents having lengths of 24 mm and 46 mm in length. A
circumference of the stent 10 varies along a length thereof, but is
generally sized for receiving a bicuspid or tricuspid valve. An
example circumference of the stent at a point in the upper portion
is 30 mm, but other sizes can be used depending on the desired
valve. The stent can be a self-expanding stent formed from a shape
memory material, such as, for example, Nitinol. In the illustrated
embodiment, the stent is formed from multiple somewhat
arcuate-shaped fibers extending along the length of the stent with
approximately half of the fibers bent in a first direction and half
of the fibers bent in a second direction to create a criss-cross
pattern. As explained further below, the stent can be delivered in
a radially-compressed state using an introducer, such that after
reaching the treatment site, it is advanced out of the distal end
of the introducer and expands to its functional size in a relaxed
state in contact with the surrounding tissue. A specific example of
such a technique is shown and described below in relation to FIGS.
8A-8D.
[0036] In other embodiments, the stent 10 can be a
balloon-expandable stent. In such a case, the stent can be formed
from stainless steel or any other suitable materials. The
balloon-expandable stent can be configured to be crimped to a
reduced diameter and placed over a deflated balloon on the distal
end portion of an elongate balloon catheter, as is well-understood
in the art.
[0037] The flared end 14 of the stent 10 helps to secure the stent
above or below the annulus of the native mitral valve (depending on
the procedure used), while the tapered portion is shaped for being
held in place by the native leaflets of the mitral valve.
[0038] FIGS. 2A and 2B are perspective views of the stent 10 with a
valve 18 inserted therein to form a mitral valve assembly 20. The
valve 18 can have a leafed-valve configuration, such as a bicuspid
valve configuration or the tricuspid valve configuration shown in
the illustrated embodiment. As shown in FIG. 2B, the valve 18 can
be formed from three pieces of flexible, pliant material connected
to each other at seams 60 (also referred to as commissure tabs) to
form collapsible leaflets 62 and a base, or upper end, portion 64.
The valve 18 can be connected to the stent 10 at the seams 60
using, for example, sutures or other suitable connection techniques
well-known in the art. Alternatively, the valve 18 can be a
mechanical type valve, rather than a leafed type valve.
[0039] The valve 18 can be made from biological matter, such as
natural tissue, pericardial tissue (e.g., bovine, porcine or equine
pericadium), a harvested natural valve, or other biological tissue.
Alternatively, the valve can be made from biocompatible synthetic
materials (e.g., biocompatible polymers), which are well known in
the art. The valve can be shaped to fit the contours of the stent
so as to have a flared upper end portion having an upper
circumference larger than a lower circumference at the lower end of
the valve. Blood flow through the valve proceeds in a direction
from the upper portion 12 to the lower portion 16, as indicated by
arrow 22 (FIG. 2A).
[0040] FIG. 3 shows a cross-sectional view of a heart with the
prosthetic mitral-valve assembly inserted into the native mitral
valve. For purposes of background, the four-chambered heart is
explained further. On the left side of the heart, the native mitral
valve 24 is located between the left atrium 26 and left ventricle
28. The mitral valve generally comprises two leaflets, an anterior
leaflet 24a and a posterior leaflet 24b. The mitral valve leaflets
are attached to a mitral valve annulus 30, which is defined as the
portion of tissue surrounding the mitral valve orifice. The left
atrium 26 receives oxygenated blood from the pulmonary veins. The
oxygenated blood that is collected in the left atrium 26 enters the
left ventricle 28 through the mitral valve 24.
[0041] Contraction of the left ventricle 28 forces blood through
the left ventricular outflow tract and into the aorta 32. The
aortic valve 34 is located between the left ventricle 28 and the
aorta 32 for ensuring that blood flows in only one direction (i.e.,
from the left ventricle to the aorta). As used herein, the left
ventricular outflow tract (LVOT) is intended to generally include
the portion of the heart through which blood is channeled from the
left ventricle to the aorta.
[0042] On the right side of the heart, the tricuspid valve 40 is
located between the right atrium 42 and the right ventricle 44. The
right atrium 42 receives blood from the superior vena cava 46 and
the inferior vena cava 48. The superior vena cava 46 returns
de-oxygenated blood from the upper part of the body and the
inferior vena cava 48 returns de-oxygenated blood from the lower
part of the body. The right atrium 42 also receives blood from the
heart muscle itself via the coronary sinus. The blood in the right
atrium 42 enters into the right ventricle 44 through the tricuspid
valve 40. Contraction of the right ventricle forces blood through
the right ventricle outflow tract and into the pulmonary arteries.
The pulmonic valve 50 is located between the right ventricle 44 and
the pulmonary trunk for ensuring that blood flows in only one
direction from the right ventricle to the pulmonary trunk.
[0043] The left and right sides of the heart are separated by a
wall generally referred to as the septum 52. The portion of the
septum that separates the two upper chambers (the right and left
atria) of the heart is termed the artial (or interatrial) septum
while the portion of the septum that lies between the two lower
chambers (the right and left ventricles) of the heart is called the
ventricular (or interventricular) septum. A healthy heart has a
generally conical shape that tapers from a base to an apex 54.
[0044] As shown in FIG. 3, the mitral valve assembly 20 is
positioned such that the flared end 14 of the upper portion 12 is
adjacent the annulus 30 of the native mitral valve 24, while the
leaflets of the native valve bear against and hold the tapered
upper end portion 12 of the mitral valve assembly. The prosthetic
mitral valve assembly of FIG. 3 is preferably positioned with the
flared end 14 above or just below an annulus 30 of the native
mitral valve. The valve assembly is configured to form a "pressure
fit" with the surrounding native valve tissue; that is, the outward
radial pressure of the stent bears against the surrounding tissue
to assist in retaining the valve assembly in place.
[0045] FIG. 4 is enlarged view of the mitral valve assembly 20
positioned below the annulus 30 of the native mitral valve 24. In
particular, the flared end 14 of the stent is tucked under the
annulus 30 of the native mitral valve (under the insertion point of
the mitral leaflets to the left atrium), but on top of the mitral
valve leaflets 24a, 24b. When deployed in this position, the mitral
valve assembly exerts sufficient radial pressure outwardly to press
into the native tissue, as the shape-memory material exerts an
outward radial force to return the assembly to its expanded shape.
As a result of the positioning of the flared end 14, the annulus 30
protrudes slightly inwardly past the flared end of the stent and
acts as an annular mechanical stop preventing upward movement of
the mitral valve assembly 20. The amount of outward radial pressure
exerted by the mitral valve assembly 20 depends partly on the size
of the stent and the type of shape-memory material used. The stent
size can depend on the particular patient and the desired amount of
pressure needed to hold the prosthetic mitral valve in place. The
tapered upper portion 12 of the mitral valve assembly 20 desirably
is shaped to fit the contours of the native mitral valve leaflets
24a, 24b, which bear against the outer surface of the stent and
prevent downward motion of the assembly. Thus, due to the unique
shape of the mitral valve assembly 20, it can be held in place
solely by the pressure exerted by the stent radially outwardly
against the surrounding tissue without the use of hooks, prongs,
clamps or other grasping device.
[0046] When properly positioned, the valve assembly avoids or at
least minimizes paravalvular leakage. In tests performed on a
porcine heart, approximately two pounds of force or greater were
applied to stents in the left atrial direction with little or no
dislodgement, movement or disorientation.
[0047] FIG. 5 shows an alternative positioning of the mitral valve
assembly. In this position, the mitral valve assembly 20 can be
secured above the native mitral valve annulus 30. The mitral valve
leaflets 24a, 24b still prevent downward movement of the mitral
valve assembly. However, to assist in preventing upward movement,
the mitral valve assembly 20 can be anchored using a tether 80
coupled between a lower portion of the mitral valve assembly (such
as by being tied to the stent) and a portion of the heart (e.g., an
opposing wall). In the particular embodiment shown, the tether 80
extends through the apex 54 of the heart and is secured in place by
an enlarged head portion 84 connected to the lower end of the
tether outside of the apex. The tether and/or head portion can be
formed of a bioresorbable material so that it eventually dissolves
after the stent has grown into the wall of the native mitral
valve.
[0048] FIG. 6 shows another embodiment of a mitral valve assembly
100 that may be used with supra-annular positioning. In particular,
an outer surface of a stent 102 includes anchoring members, such
as, for example, prongs 104 in the form of upwardly bent hooks,
that can penetrate the surrounding tissue to prevent upward
migration of the assembly 100 when in place. The anchoring members
may be made from the same material as the stent, but alternative
materials may also be used.
[0049] FIG. 7 shows another embodiment of a stent 110 that can be
used. In this embodiment, an upper portion 112 of the stent is
scalloped (i.e., the upper edge has one or more indented or cut-out
portions 114). In some patients, the pressure exerted by the upper
rim of the stent on the anterior mitral leaflet can displace the
mitral curtain and anterior leaflet toward the left ventricular
outflow track. The stent can be deployed such that the anterior
leaflet is generally positioned within a cutout (scalloped) portion
of the stent. In this manner, the scalloped stent 110 reduces the
pressure on the leaflet to ensure there is no alteration of blood
flow in the left ventricle.
[0050] FIGS. 8A-8D depict an embodiment of a transapical procedure
for inserting the prosthetic mitral valve assembly into the native
mitral valve. The replacement procedure is typically accomplished
by implanting the prosthetic mitral valve assembly directly over
the native leaflets, which are typically calcified. In this manner,
the native leaflets 24a, 24b can assist in securing the mitral
valve assembly in place.
[0051] First, an incision is made in the chest of a patient and in
the apex 54 of the patient's heart. A guide wire 120 is inserted
through the apex 54 and into the left ventricle. The guide wire 120
is then directed up through the mitral valve 24 and into the left
atrium 26. An introducer 122 is advanced over the guide wire into
the left atrium (see FIGS. 8A and 8B). A delivery catheter 124 is
inserted through the introducer (see FIG. 8B). A prosthetic valve
assembly 20 is retained in a crimped state on the distal end
portion of the delivery catheter as the valve assembly and delivery
catheter are advanced through the introducer. In one variation, the
introducer 122 is formed with a tapered distal end portion 123 to
assist in navigating through the chordae tendinae. The delivery
catheter 124 likewise can have a tapered distal end portion
126.
[0052] In FIG. 8C, the introducer 122 is retracted relative to the
mitral valve assembly 20 for deploying the mitral valve assembly
from the distal end of the introducer. To pull the valve assembly
20 into position at the intended implantation site, the valve
assembly desirably is partially advanced out of the introducer to
expose the flared upper end portion 12, while the remainder of the
valve assembly remains compressed within the introducer (as shown
in FIG. 8C). As shown, the flared end portion expands when advanced
from the distal end of the introducer. The delivery catheter 124
and the introducer 122 can then be retracted together to pull the
flared end into the desired position (e.g., just below the annulus
of the native valve). Thereafter, the introducer can be further
retracted relative to the delivery catheter to advance the
remaining portion of the valve assembly 20 from the introducer,
thereby allowing the entire assembly to expand to its functional
size, as shown in FIG. 8D. The introducer and catheter can then be
withdrawn from the patient.
[0053] Alternatively, the mitral valve assembly can be fully
expanded directly in place at the implantation site by first
aligning the valve assembly at the implantation site and then
retracting the introducer relative to the delivery catheter to
allow the entire valve assembly to expand to its functional size.
In this case, there is no need to pull the mitral valve assembly
down into the implantation site. Additional details of the
transapical approach are disclosed in U.S. Patent Application
Publication No. 2007/0112422 (mentioned above).
[0054] In another embodiment, the valve assembly 20 can be mounted
on an expandable balloon of a delivery catheter and expanded to its
functional size by inflation of the balloon. When using a balloon
catheter, the valve assembly can be advanced from the introducer to
initially position the valve assembly in the left atrium 26. The
balloon can be inflated to fully expand the valve assembly. The
delivery catheter can then be retracted to pull the expanded valve
assembly into the desired implantation site (e.g., just below the
annulus of the native valve). In another embodiment, the balloon
initially can be partially inflated to partially expand the valve
assembly in the left atrium. The delivery catheter can then be
retracted to pull the partially expanded valve into the
implantation site, after which the valve assembly can be fully
expanded to its functional size.
[0055] Mitral regurgitation can occur over time due to the lack of
coaptation of the leaflets in the prosthetic mitral valve assembly.
The lack of coaptation in turn can lead to blood being regurgitated
into the left atrium, causing pulmonary congestion and shortness of
breath. To minimize regurgitation, the leaflets of the valve
assembly can be connected to one or more tension members that
function as prosthetic chordae tendinae.
[0056] FIG. 9, for example, shows an embodiment comprising a
prosthetic mitral valve assembly 152 having leaflets 154. Each
leaflet 154 can be connected to a respective tension member 160,
the lower ends of which can be connected at a suitable location on
the heart. For example, the lower end portions of tension members
160 can extend through the apex 54 and can be secured at a common
location outside the heart. Tension members may be attached to or
through the papillary muscles. The lower ends of tension members
can be connected to an enlarged head portion, or anchor, 164, which
secures the tension members to the apex. Tension members 160 can
extend through a tensioning block 166. The tensioning block 166 can
be configured to slide upwardly and downwardly relative to tension
members 160 to adjust the tension in the tensioning members. For
example, sliding the tensioning block 166 upwardly is effective to
draw the upper portions of the tension members closer together,
thereby increasing the tension in the tension members. The
tensioning block 166 desirably is configured to be retained in
place along the length of the tension members, such as by crimping
the tensioning block against the tension members, once the desired
tension is achieved. The tension members can be made of any
suitable biocompatible material, such as traditional suture
material, GORE-TEX.RTM., or an elastomeric material, such as
polyurethane. The tension members 160 further assist in securing
the valve assembly in place by resisting upward movement of the
valve assembly and prevent the leaflets 154 from everting so as to
minimize or prevent regurgitation through the valve assembly. As
such, the tethering de-stresses the moveable leaflets, particularly
during ventricular systole (i.e., when the mitral valve is closed).
Alternatively or in addition, the stent 10 can be connected to one
or more tension members 160 for stabilizing the mitral valve
assembly during the cyclic loading caused by the beating heart.
[0057] FIG. 10 shows another embodiment of a mitral valve assembly
152 having prosthetic chordae tendinae. The prosthetic chordae
tendinae comprise first and second tension members 170 connected to
a respective leaflet 154 of the valve assembly. As shown, the lower
end portions 172 of each tension member 170 can be connected at
spaced apart locations to the inner walls of the left ventricle,
using, for example, anchor members 174. A slidable tensioning block
176 can be placed over each tension member 170 for adjusting the
tension in the corresponding tension member. In certain
embodiments, each tension member 170 can comprise a suture line
that extends through a corresponding leaflet 154 and has its
opposite ends secured to the ventricle walls using anchor members
174.
[0058] In particular embodiments, the anchor member 174 can have a
plurality of prongs that can grab, penetrate, and/or engage
surrounding tissue to secure the device in place. The prongs of the
anchor member 174 can be formed from a shape memory material to
allow the anchor member to be inserted into the heart in a radially
compressed state (e.g., via an introducer) and expanded when
deployed inside the heart. The anchor member can be formed to have
an expanded configuration that conforms to the contours of the
particular surface area of the heart where the anchor member is to
be deployed, such as described in co-pending Application No.
11/750,272, published as US 2007/0270943 A1, which is incorporated
herein by reference. Further details of the structure and use of
the anchor member are also disclosed in co-pending application Ser.
No. 11/695,583 to Rowe, filed Apr. 2, 2007, which is incorporated
herein by reference.
[0059] Alternative attachment locations in the heart are possible,
such as attachment to the papillary muscle (not shown). In
addition, various attachment mechanisms can be used to attach
tension members to the heart, such as a barbed or screw-type anchor
member. Moreover, any desired number of tension members can be
attached to each leaflet (e.g., 1, 2, 3 . . . etc.). Further, it
should be understood that tension members (e.g., tension members
160 or 170) can be used on any of the embodiments disclosed
herein.
[0060] As discussed above, FIGS. 9-10 show the use of tension
members that can mimic the function of chordae. The tethers can
have several functions including preventing the valve from
migrating into the left atrium, de-stressing the leaflets by
preventing eversion, and preserving ventricular function by
maintaining the shape of the left ventricle. In particular, the
left ventricle can lose its shape over time as the natural chordae
become stretched or break. The artificial chordae can help to
maintain the shape. Although FIGS. 9 and 10 show a tricuspid valve,
a bicuspid valve can be used instead. Particular bicuspid valves
are shown in FIGS. 12-16.
[0061] FIG. 11 shows another embodiment of a mitral valve assembly
190 including a valve 192 and a stent 194 (shown partially cut-away
to expose a portion of the valve). Tension members, shown generally
at 196, can be connected between leaflets 198, 200 of the valve 192
and the stent itself. Only two leaflets are shown, but additional
tension members can be used for a third leaflet in a tricuspid
valve. In the illustrated embodiment, the tension members 196 can
include groups 202, 204 of three tension members each. The three
tension members 196 of group 202 can be attached, at one end, to
leaflet 198 at spaced intervals and converge to attach at an
opposite end to a bottom 206 of the stent 194. Group 204 can be
similarly connected between leaflet 200 and the bottom 206 of the
stent 194. The tension members 196 can be made of any suitable
biocompatible material, such as traditional suture material,
GORE-TEX.RTM., or an elastomeric material, such as polyurethane.
The tension members can prevent the leaflets 198, 200 from everting
so as to minimize or prevent regurgitation through the valve
assembly. As such, the tension members de-stress the moveable
portions of the leaflets when the leaflets close during systole
without the need to connect the tension members to the inner or
outer wall of the heart.
[0062] Although groups of three tension members are illustrated,
other connection schemes can be used. For example, each group can
include any desired number of tension members (e.g., 1, 2, 3, . . .
etc.). Additionally, the tension members can connect to any portion
of the stent 194 and at spaced intervals, if desired. Likewise, the
tension members can connect to the leaflets at a point of
convergence, rather than at spaced intervals. Further, the tension
members can be used on bicuspid or tricuspid valves. Still further,
it should be understood that tension members extending between the
stent and the leaflets can be used on any of the embodiments
disclosed herein.
[0063] FIGS. 12-14 show another embodiment of a mitral valve
assembly 220 including a bicuspid valve 222 mounted within a stent
224. The bicuspid valve 222 can include two unequally-sized
leaflets, 226, 228. FIG. 12 shows a perspective view of the mitral
valve assembly 220 with the bicuspid valve 222 in an open position
with blood flow shown by directional arrow 230. FIG. 14 shows a top
view of the mitral valve assembly 220 with the valve 222 in the
open position. FIG. 13 shows a top view of the mitral valve
assembly 220 with the bicuspid valve 222 in a closed position. The
leaflet 226 is shown as a larger leaflet than leaflet 228 with the
leaflets overlapping in a closed or at-rest position. The
overlapping configuration can provide sufficient closure of the
valve to prevent central or coaptation leakage and can enhance
valve durability by eliminating or minimizing impacts on the
leaflet touching or coaptation. The bicuspid valve 222 can be used
with any of the stent configurations described herein.
[0064] FIGS. 15 and 16 show another embodiment of a mitral valve
assembly 240 including a bicuspid valve 242 mounted within a stent
243. Tension members, shown generally at 244, can be connected
between leaflets 246, 248 of the valve and the stent itself.
Leaflet 246 is shown as a larger leaflet that overlaps leaflet 248.
FIG. 15 shows the mitral valve assembly 240 in a closed position
with the tension members 244 at full extension. FIG. 16 shows the
bicuspid valve 242 in the open position with the tension members
244 in a relaxed or slack state. Although the tension members 244
are shown attached at the same relative vertical position or height
on the stent 243, the tension members 244 can be attached
asymmetrically relative to each other. In other words, the tension
members 244 can be attached at different heights along the length
of the stent. Additionally, the tension members 244 can differ in
length in order to achieve the asymmetrical coupling between the
leaflets 246, 248 and the stent 243. The tensioning members 244 can
be used on any of the mitral valve assembly embodiments described
herein.
[0065] FIG. 17 shows a top view of a mitral valve assembly 260
having a non-uniform cross-sectional shape. The mitral valve
assembly 260 can have a shape configured to conform to the natural
opening of the native mitral valve. For example, the mitral valve
assembly 260 can have a substantially "D" shape, with a
substantially straight portion 262 and a substantially curved
portion 264. When implanted, the substantially straight portion 262
can extend along the anterior side of the native mitral valve and
the substantially curved portion 264 of the stent can extend along
the posterior side of the native mitral valve. Other shapes may
also be used.
[0066] Having illustrated and described the principles of the
illustrated embodiments, it will be apparent to those skilled in
the art that the embodiments can be modified in arrangement and
detail without departing from such principles.
[0067] Although the transapical procedure shown in FIGS. 8A-8D
illustrates positioning and deployment of mitral valve assembly 20,
other embodiments of the mitral valve assembly disclosed herein can
be implanted using the same procedure, such as the mitral valve
assembly 100 of FIG. 6, or a mitral valve assembly using the stent
of FIG. 7.
[0068] Further, although the mitral valve assembly 20 is shown
generally circular in cross section, as noted above, it can have a
D-shape, an oval shape or any other shape suitable for fitting the
contours of the native mitral valve. Furthermore, although the
mitral valve assembly is shown as having a flared upper end, other
embodiments are contemplated, such as, for example, wherein the
stent is flared at both ends or has a substantially cylindrical
shape. Furthermore, the stent may be coated to reduce the
likelihood of thrombi formation and/or to encourage tissue ingrowth
using coatings known in the art. Still further, it is contemplated
that the stent may be replaced with an alternative structure, such
as an expandable tubular structure, which is suitable for anchoring
the prosthetic valve member in the heart.
[0069] Still further, although a transapical procedure is described
in detail in FIGS. 8A-8D, other procedures can be used in
conjunction with the above-described embodiments. For example, U.S.
Patent Publication 2004/0181238, to Zarbatany et al., entitled
"Mitral Valve Repair System and Method for Use", which is hereby
incorporated by reference, discloses a percutaneous delivery
approach. A guidewire capable of traversing the circulatory system
and entering the heart of the patient can be introduced into the
patient through an endoluminal entry point, such as the femoral
vein or the right jugular vein. The guidewire can then be directed
into the right atrium where it traverses the right atrium and
punctures the atrial septum using a tran-septal needle. The
guidewire can then be advanced through the atrial septum, through
the left atrium and through the mitral valve. Once the guidewire is
properly positioned, a guide catheter can be attached to the
guidewire and advanced proximate the native mitral valve. A
delivery catheter for delivery of the prosthetic mitral valve can
then be advanced through the guide catheter to deploy the
prosthetic valve within the native mitral valve. Various delivery
catheters can be used, such as those described in Zarbatany, as
well as those described U.S. Patent Publication 2007/0088431, to
Bourang et al., entitled "Heart Valve Delivery System With Valve
Catheter" and U.S. Patent Publication U.S. 2007/0005131, to Taylor,
entitled "Heart Valve Delivery System", both of which are hereby
incorporated by reference.
[0070] In view of the many possible embodiments, it will be
recognized that the illustrated embodiments include only examples
of the invention and should not be taken as a limitation on the
scope of the invention. Rather, the invention is defined by the
following claims. We therefore claim as the invention all such
embodiments that come within the scope of these claims.
* * * * *