U.S. patent application number 12/614878 was filed with the patent office on 2010-05-27 for artificial valve prosthesis with improved flow dynamics.
This patent application is currently assigned to COOK INCORPORATED. Invention is credited to Brian C. Case, Jacob A. Flagle, Michael L. Garrison, Andrew Hoffa, Darin G. Schaeffer.
Application Number | 20100131055 12/614878 |
Document ID | / |
Family ID | 33423545 |
Filed Date | 2010-05-27 |
United States Patent
Application |
20100131055 |
Kind Code |
A1 |
Case; Brian C. ; et
al. |
May 27, 2010 |
ARTIFICIAL VALVE PROSTHESIS WITH IMPROVED FLOW DYNAMICS
Abstract
An expandable venous valve having a support structure configured
to enlarge the area adjacent the valve structure. The enlarged
pocket areas can be created by forming an artificial sinus adjacent
the valve structure in an unsupported section of vessel wall
between two support frame sections.
Inventors: |
Case; Brian C.;
(Bloomington, IN) ; Garrison; Michael L.;
(Indianapolis, IN) ; Hoffa; Andrew; (Bloomington,
IN) ; Schaeffer; Darin G.; (Bloomington, IN) ;
Flagle; Jacob A.; (Indianapolis, IN) |
Correspondence
Address: |
BUCHANAN INTELLECTUAL PROPERTY OFFICE LLC
P.O. BOX 700
PERRYSBURG
OH
43552-0700
US
|
Assignee: |
COOK INCORPORATED
Bloomington
IN
|
Family ID: |
33423545 |
Appl. No.: |
12/614878 |
Filed: |
November 9, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10554494 |
Mar 13, 2007 |
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PCT/US04/12430 |
Apr 21, 2004 |
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12614878 |
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60465141 |
Apr 24, 2003 |
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60530781 |
Dec 18, 2003 |
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Current U.S.
Class: |
623/2.17 |
Current CPC
Class: |
A61F 2220/0016 20130101;
A61F 2250/0039 20130101; A61F 2002/068 20130101; A61F 2/2418
20130101; A61F 2230/0076 20130101; A61F 2250/0037 20130101; A61F
2230/008 20130101; A61F 2230/0078 20130101; A61F 2/2475 20130101;
A61F 2220/0008 20130101; A61F 2230/0054 20130101 |
Class at
Publication: |
623/2.17 |
International
Class: |
A61F 2/24 20060101
A61F002/24 |
Claims
1-29. (canceled)
30. A radially expandable artificial valve prosthesis for
implantation in a vessel having a vessel wall, comprising: a
support structure, comprising: a proximal section comprising a
first radially expandable anchoring portion having a plurality of
struts interconnected by bends; a distal section comprising a
second radially expandable anchoring portion having a plurality of
struts interconnected by bends; the proximal and distal sections
spaced apart from one another to define an intermediate section
disposed between the proximal and distal sections, the intermediate
section comprising a substantially open section of the support
structure; a first connection strut connected with the proximal and
distal sections and spanning the intermediate section; and a second
connection strut connected with the proximal and distal sections
and spanning the intermediate section; and a valve structure
attached to the support structure and configured to selectively
restrict fluid flow through the support structure by closing with
changes in the fluid pressure differential across said valve
prosthesis.
31. The radially expandable valve prosthesis of claim 30, wherein
the valve structure is situated in the intermediate section of the
support structure.
32. The radially expandable valve prosthesis of claim 31, wherein
the intermediate section has a first length the extends along a
lengthwise axis of said valve prosthesis; wherein the valve
structure has a second length that extends along the lengthwise
axis of said valve prosthesis; and wherein the first length is
greater than the second length.
33. The radially expandable artificial valve prosthesis of claim
30, wherein the proximal section defines a first circumference and
the first connection strut is connected with a first attachment
point on the first circumference; and wherein the distal section
defines a second circumference and the first connection strut is
connected with a second attachment point on the second
circumference; and wherein the first and second attachment points
lie on a first longitudinal axis of said artificial valve
prosthesis.
34. The radially expandable artificial valve prosthesis of claim
33, wherein the second connection strut is connected with a third
attachment point on the first circumference; and wherein the second
connection strut is connected with a fourth attachment point on the
second circumference; and wherein the third and fourth attachment
points lie on a second longitudinal axis of said artificial valve
prosthesis that is different than the first longitudinal axis.
35. The radially expandable artificial valve prosthesis of claim
34, wherein the first and second longitudinal axes are disposed
substantially opposite each other with respect to a
centrally-disposed longitudinal axis of said valve prosthesis.
36. The radially expandable artificial valve prosthesis of claim
30, wherein the proximal section defines a first circumference and
the first connection strut is connected with a first attachment
point on the first circumference; and wherein the distal section
defines a second circumference and the first connection strut is
connected with a second attachment point on the second
circumference; and wherein the first attachment point lies on a
first longitudinal axis of said artificial valve prosthesis and the
second attachment point lies on a second, different longitudinal
axis of said valve prosthesis.
37. The radially expandable valve prosthesis of claim 36, wherein
the first and second attachment points are approximately 90.degree.
out of phase with each other relative to a centrally-disposed
longitudinal axis of said valve prosthesis.
38. The radially expandable valve prosthesis of claim 36, wherein
the second connection strut is connected with the first attachment
point on the first circumference and a third attachment point on
the second circumference; wherein the third attachment point lies
on a third, different longitudinal axis of said artificial valve
prosthesis.
39. The radially expandable valve prosthesis of claim 30, wherein
the first and second connection struts comprise linear struts
disposed substantially opposite each other with respect to a
centrally-disposed longitudinal axis of said valve prosthesis.
40. The radially expandable valve prosthesis of claim 30, wherein
the intermediate section includes interconnecting structure
consisting of the first and second connection struts.
41. The radially expandable valve prosthesis of claim 30, wherein
the valve structure is attached to the first and second connection
struts.
42. The radially expandable valve prosthesis of claim 30, wherein
the valve structure comprises a single leaflet.
43. The radially expandable valve prosthesis of claim 30, wherein
the valve structure comprises two leaflets.
44. The radially expandable valve prosthesis of claim 30, wherein
the valve structure comprises a synthetic material.
45. The radially expandable valve prosthesis of claim 44, wherein
the valve structure comprises DACRON.
46. The radially expandable valve prosthesis of claim 44, wherein
the valve structure comprises ePTFE.
47. The radially expandable valve prosthesis of claim 30, wherein
the valve structure comprises a biologically-derived material.
48. The radially expandable valve prosthesis of claim 47, wherein
the valve structure comprises a bioremodellable material.
49. The radially expandable valve prosthesis of claim 48, wherein
the valve structure comprises an extracellular matrix material.
50. The radially expandable valve prosthesis of claim 49, wherein
the valve structure comprises small intestine submucosa.
51. The radially expandable valve prosthesis of claim 30, wherein
the support structure comprises a metal.
52. The radially expandable valve prosthesis of claim 51, wherein
the support structure comprises stainless steel.
53. The radially expandable valve prosthesis of claim 51, wherein
the support structure comprises a superelastic material.
54. The radially expandable valve prosthesis of claim 53, wherein
the superelastic material comprises nitinol.
55. The radially expandable valve prosthesis of claim 30, wherein
the support structure comprises a polymeric material.
56. A radially expandable artificial valve prosthesis for
implantation in a vessel having a vessel wall, comprising: a
support structure, comprising: a proximal section comprising a
first radially expandable anchoring portion having a plurality of
struts interconnected by bends and defining a first circumference;
a distal section comprising a second radially expandable anchoring
portion having a plurality of struts interconnected by bends and
defining a second circumference; the proximal and distal sections
spaced apart from one another to define an intermediate section
disposed between the proximal and distal sections, the intermediate
section comprising a substantially open section of the support
structure; and first and second connection struts spanning the
intermediate section and connected with the proximal and distal
sections, each of the first and second connection struts connected
with a first attachment point on the first circumference; and a
valve structure attached to the support structure and configured to
selectively restrict fluid flow through the support structure by
closing with changes in the fluid pressure differential across said
valve prosthesis.
57. A radially expandable artificial valve prosthesis for
implantation in a vessel having a vessel wall, comprising: a
support structure, comprising: a proximal section comprising a
first radially expandable anchoring portion having a plurality of
struts interconnected by bends and defining a first circumference;
a distal section comprising a second radially expandable anchoring
portion having a plurality of struts interconnected by bends and
defining a second circumference; the proximal and distal sections
spaced apart from one another to define an intermediate section
disposed between the proximal and distal sections, the intermediate
section comprising a substantially open section of the support
structure; and first and second curvilinear connection struts
spanning the intermediate section and connected with the proximal
and distal sections, each of the first and second curvilinear
connection struts connected with a first attachment point on the
first circumference and a second attachment point on the second
circumference; and a valve structure attached to the support
structure and configured to selectively restrict fluid flow through
the support structure by closing with changes in the fluid pressure
differential across said valve prosthesis.
Description
TECHNICAL FIELD
[0001] This invention relates to medical devices, more particularly
to intravascular valve prostheses and the like.
BACKGROUND OF THE INVENTION
[0002] The venous system includes a series of valves that function
to assist the flow of blood returning to the heart. These natural
valves are particularly important in the lower extremities to
prevent blood from pooling in the lower legs and feet during
situations, such as standing or sitting, when the weight of the
column of blood in the vein can act to prevent positive blood flow
toward the heart. This condition, commonly known as `chronic venous
insufficiency`, is primarily found in individuals in which gradual
dilation of the veins, thrombotic events, or other conditions
prevent the leaflets of the native valves from closing properly.
This leads to significant leakage of retrograde flow such that the
valve is considered `incompetent`. Chronic venous insufficiency is
a potentially serious condition in which the symptoms can progress
from painful edema and unsightly spider or varicose veins to skin
ulcerations. Elevation of the feet and compression stocking can
relieve symptoms, but do not treat the underlying disease.
Untreated, the disease can impact the ability of individuals to
perform in the workplace or maintain their normal lifestyle.
[0003] To treat venous valve insufficiency, a number of surgical
procedures have been employed to improve or replace the native
valve, including placement of artificial valve prosthesis. These
efforts have met with limited success and have not been widely
adopted as a method of treating chronic venous insufficiency. More
recently, the search has been to find a suitable self-expanding or
radially-expandable artificial valve that can be placed using
minimally invasive techniques rather than requiring open surgery
and its obvious disadvantages. Thus far, use of prosthetic venous
valves has remained experimental only.
[0004] While attempts have been made to mimic the function of the
natural valve, there is no expandable valve for venous
transcatheter placement that includes a combination of the native
structural features that individually or collectively, may prove
highly advantageous or critical for a successful valve. One common
problem evident from early experiences with prosthetic valves is
the formation of thrombus around the base of the leaflets, probably
due at least in part to blood pooling in that region. In a natural
valve, the leaflets are typically located within a sinus or
enlargement in the vein. There is some evidence that the pockets
formed between the leaflets and the walls of the sinus create
vortices of flowing blood that help flush the pocket and prevent
blood from stagnating and causing thrombosis around the valve
leaflets, which can interfere with the function of the valve. It is
thought that the stagnating blood prevents oxygen from reaching the
endothelium covering the valve cusps, leading to hypoxia of the
tissues which may explain increased thrombus formation typical in
that location. Expandable-frame valve prostheses typically are of a
generally cylindrical in shape and lack an artificial sinus or
pocket space that is sufficient for simulating these natural blood
flow patterns. What is needed is an intravenously placed artificial
valve that is configured to create more effective flow patterns
around the valve structure to circulate the blood or bodily fluids
and reduce the likelihood of stagnation and the potential clinical
problems that may result.
SUMMARY OF THE INVENTION
[0005] The foregoing problems are solved and a technical advance is
achieved in an illustrative valve prosthesis, such as an artificial
venous valve, having a valve structure and a self-expanding or
otherwise expandable support structure that upon deployment within
the vein, helps create an artificial sinus or larger pocket in the
vessel surrounding the valve structure of sufficient size and shape
to stimulate flow patterns or vortices which facilitate clearing of
the blood or other bodily fluid that would otherwise pool therein.
The structural adaptations result in more turbulent flow, increased
velocity of flow, larger and/or more numerous vortices, other
factors, or a combination of the above that prevent stagnant,
hypoxic areas from occurring around the valve structure.
Furthermore, the modified flow may also contribute to helping close
the leaflets to form a seal and prevent leakage of fluid back
through the valve. The artificial sinus or enlarged pockets
simulate the function of the natural sinus that exists at the site
of most natural valves in the deep veins of the lower legs and
which may explain why the problem of thrombus forming around the
valve structure has been observed to be a common problem in
prosthetic venous valve designs lacking such a sinus area.
[0006] In one aspect of the invention, the collapsible support
structure of the valve prosthesis is expandable to a particular
diameter upon deployment, with the valve prosthesis being
configured such that the prosthesis includes an intermediate,
substantially `open` section such that the artificial sinus is
created by a portion of the duct or vessel that is substantially
unsupported by the support structure. The unsupported portion of
the vessel can advantageously assume a diameter that is larger than
the deployment diameter of the vessel-anchoring or `closed`
sections or portions of the collapsible support structure, thereby
creating an artificial sinus as blood (or bodily fluid) exerts
pressure on the unsupported portion of the vessel wall. In one
exemplary embodiment, the expandable support structure comprises a
first, proximal portion and a second, distal portion that are
interconnected by one or more thin members or struts, such that the
largely unsupported region between the first and second (proximal
and distal) sections of the support structure forms an artificial
sinus (proximal being defined herein as have the same positional
orientation as the orifice or opening of the valve structure, which
is typically toward the heart in a venous valve). The valve
structure is attached about the support structure such that it is
largely situated within the unsupported region forming the
artificial sinus. For example, the valve structure (defined herein
as one or more cooperating leaflets, tubular members, or any
flexible structure adapted to seal a passageway in response to
changing fluid pressure differentials thereacross) may be attached
to the interconnecting members, which can comprise oppositely
placed struts having attachment points, (e.g., suture or any
suitable structure or method) to facilitate attachment of the valve
material.
[0007] In another aspect of the invention, the expandable support
structure of the valve prosthesis comprises a framework or
anchoring portion having an intermediate region that includes an
enlarged diameter configured to create an artificial sinus about
the valve structure, which is attached inside the intermediate
region. In one embodiment, the support structure is made of a
superelastic material, such as nitinol, and the intermediate region
comprises an expanded or bulging portion that is formed by heat
setting the nitinol tubular frame around a mandril or other fixture
of the desired configuration using a method well known in the
medical arts. The intermediate portion expands to a diameter larger
than the proximal and distal portions when the prosthesis is
deployed from the delivery system, thereby producing larger pockets
around the valve structure which create more effective flow
patterns to reduce pooling. In another embodiment, the proximal,
distal, and intermediate sections are separate, interconnected
sections, such as zig-zag frame or other expandable or
self-expanding support or anchoring frames. The intermediate
section comprising the artificial sinus includes a first and a
second radially expandable or self-expanding portions in which the
adjoining ends of each are larger in diameter than the ends which
adjoin the proximal and distal sections, respectively. The
frustoconical shape of the respective intermediate sections can be
accomplished by either forming the section into that shape (i.e.,
plastic deformation of a tubular prosthesis, heat setting nitinol,
laser cutting a frustoconical section of tubing, etc.) or a
constraining means, such as a suture or thin wire, can be used to
manipulate the relative diameters by feeding the constraining means
through the apices of the bend or apertures therein and applying
the appropriate amount of tension to create the desired shape.
Optionally, a tubular or band-like section can be positioned
between opposing frustoconical sections to create a longer
artificial sinus.
[0008] In yet another aspect of the invention, the proximal end of
the collapsible support at which the valve structure is located is
expanded (e.g flared outward) such that the expanded end or a
combination of the expanded end and adjacent area of the vein forms
the artificial sinus.
[0009] In still yet another aspect of the invention, the proximal
and distal sections are configured to include a substantially open
area between them with the valve structure being attached to the
distal section such that it is positioned just below the artificial
sinus. Optionally, a sleeve of a biomaterial (e.g a bioremodelable
material such as small intestinal submucosa (SIS) or another
collagenous extracellular matrix) or fabric can be attached over
the proximal and distal sections such that it forms a seal between
the prosthesis and the vessel wall, including the artificial
sinus.
[0010] In still yet another aspect of the present invention, the
support structure of the prosthesis is configured such that the
attachment pathway (defined herein as the interface between the
lateral, outer edges of the leaflets and the struts and/or vessel
walls to which they are attached to establish and define the shape
and configuration of the plurality of leaflets comprising the valve
structure as deployed) has a first, proximal portion in which the
one or more longitudinal attachment struts extending from the
proximal bends or commissures that carry and support the proximal
outer edges of the leaflets (and span the orifice) have a strongly
longitudinal orientation with respect to the longitudinal axis of
the prosthesis and valve structure, and a distal portion of the
attachment pathway that extends circumferentially (laterally) and
distally from the longitudinal axis to form the bottom or distal
edge of the outer leaflet edge or perimeter. When viewed from the
side, the support frame and attached leaflet is configured such
that the angle (angle .alpha.) formed between the opposing
leaflets, as carried along the proximal attachment pathway, is
substantially less than the angle (angle .beta.) formed between
distal attachment pathways and the vessel walls. This configuration
results in leaflets having large coaptable area relative to the
overall surface area, which improves sealing (including reducing
the effects of retraction by the valve material) and allows for
larger pockets surrounding the leaflets which, like the sinus,
facilitate the creation of larger, stronger vortices of retrograde
flow that help close the leaflets and clear away blood or fluid
that could otherwise stagnate under conditions where the
surrounding pockets are smaller in size. As used herein, the term
`retrograde flow` is defined as bodily fluid traveling in a distal
direction (toward the feet), whether due to gravitational forces,
redirection due to contact with the prosthesis or bodily lumen
walls, or by some other means.
[0011] A first embodiment of this aspect of the invention includes
a frame comprising a pair of longitudinal attachment struts
originating from each commissure bend. The struts extend in
generally longitudinal direction, diverging relatively or not at
all toward the distal end of the prosthesis before more acutely
diverging as they curve laterally and circumferentially away from
the proximal strut portions such that the transition between the
proximal and distal portions of attachment pathway comprises a bend
having a radius that is distinctly smaller than that of the
adjacent strut portions (the proximal portions being straight some
embodiments). The distal attachment pathways converge to define the
bottom outer edge of each leaflet. In a second embodiment of this
aspect of the invention, the support frame of the prosthesis
includes a pair of substantially parallel longitudinal attachment
struts to which the leaflets are attached to form the proximal
portion of the attachment pathway, and distal attachment struts
extending circumferentially and laterally outward from the
substantially parallel struts to form the distal portion of the
attachment pathway. The support frame carrying the valve structure
may be advantageously comprised of radial sections (e.g., quadrants
in a bicuspid valve) that are of an identical pattern but with
alternating orientation such as to provide for radial stability and
better expandability characteristics. The radial section not
carrying the leaflet proximal outer edges serves as lateral support
structure for adding longitudinal stability and help protecting the
leaflets from adhering to the vessel walls. The parallel struts
provide for advantageous bending and torsional characteristics such
that the frame has utility as a stent. In an alternate embodiment
of the support structure, the lateral outer edges of the opposing
leaflets can be attached to single longitudinal attachment strut
having a pair of distal struts extending laterally outward and
circumferentially to carry the bottom half of the leaflet and
define the overall shape thereof. The strut may be thicker than
adjacent struts and include aperture therealong for facilitating
attachment of the valve structure.
[0012] In still yet another aspect of the present invention, the
proximal section of the valve is wider in diameter at its proximal
end, which anchors the prosthesis in the vessel, and narrower at
the interface between the proximal and intermediate sections. This,
in combination with a leaflet structure that maximizes pocket size,
results in retrograde flow being subject to a Venturi effect which
increases flow and the strength of the vortices to close the valve
and clear the pockets of potentially stagnating fluids.
[0013] The configuration of the basic units of the support
structure and valve structure is not particularly critical for an
understanding of the invention. Numerous examples are well known in
the prior art and may be found in the disclosure of Applicant's
provisional application Ser. No. 60/403,783 entitled, `Implantable
Vascular Device,` filed Aug. 15, 2002 which is expressly
incorporated by reference herein.
BRIEF DESCRIPTION OF THE DRAWING
[0014] Embodiments of the present invention will now be described
by way of example with reference to the accompanying drawings, in
which:
[0015] FIG. 1 depicts a cross-sectional view of a native venous
valve and retrograde blood flow pattern;
[0016] FIG. 2 depicts a schematic view of an illustrative
embodiment of the present invention in which the prosthesis
includes interconnecting proximal and distal sections defining an
intermediate, substantially open section for creating an artificial
sinus in the vessel;
[0017] FIG. 3 depicts a schematic view of a second illustrative
embodiment of the present invention in which the proximal and
distal sections are interconnected by a frame that is incorporated
into the valve structure of the prosthesis;
[0018] FIG. 4 depicts a schematic view of an illustrative
embodiment of the present invention in which the intermediate
section of the prosthesis comprises an expanded portion of the
support structure;
[0019] FIG. 5 depicts a schematic view of an illustrative
embodiment of the present invention in which the proximal end is
expanded to create an artificial sinus about the valve
structure;
[0020] FIGS. 6-7 depict side views of embodiments of the present
invention in which artificial sinus comprises a plurality of
separate support sections;
[0021] FIG. 8 depicts a partially sectioned side view of an
embodiment of the present invention that includes an external
sleeve of material;
[0022] FIG. 9 depicts a perspective view of a support structure of
the present invention adapted to increase coaptation of leaflets
and pocket size within the vessel;
[0023] FIGS. 10-11 depict side views comparing the flow patterns in
a standard valve leaflet configuration with those of the embodiment
of FIG. 9; and
[0024] FIG. 12 depicts an embodiment of the present invention
having a combination of a narrowed intermediate section and the
valve structure configuration of FIG. 9.
[0025] FIG. 13 depicts a side view of an embodiment of the present
invention in which the leaflets are attached to the parallel struts
to increase the area of coaptation;
[0026] FIG. 14 depicts a side view of the embodiment of FIG. 13
that is rotated 90.degree. therefrom.
[0027] FIG. 15 depicts a top view of the embodiment of FIG. 13.
[0028] FIG. 16 depicts an unrolled view of the support frame of the
embodiment FIG. 13;
[0029] FIGS. 17-18 depict unrolled views of additional embodiments
of the present invention for increasing the area of leaflet
coaptation;
[0030] FIGS. 19-20 depict plan views of adaptations in the support
structure for affixing the valve structure thereto; and
[0031] FIG. 21 depicts a partially sectioned perspective view of an
embodiment in which the support structure does not co-extend along
the entirety of the leaflet outer edges.
DETAILED DESCRIPTION
[0032] The present invention, selected examples of which are
illustrated in FIGS. 2-9, 11-20, comprises a collapsible, self
expanding or otherwise expandable artificial valve prosthesis 10
that is deployed within a bodily passageway 20, such as a vessel or
duct, of a patient typically delivered and implanted using
well-known transcatheter techniques for self-expanding prostheses,
the valve prosthesis having a first or proximal end 13 and a second
or distal end 14, with the normal, antegrade fluid flow typically
traveling from the distal end to proximal end of the prosthesis,
the latter being located closest to the heart in a venous valve
when placed within the lower extremities of a patent. The valve
prosthesis 10 comprises a support structure 11 and a valve
structure 12, such as the illustrative valve structure, attached
about the support structure and configured to selectively restrict
fluid flowing therethrough by closing with changes in the fluid
pressure differential, such as in the presence of retrograde flow.
The present invention includes structural features that modify the
flow dynamics within the prosthesis such that fluid collecting in
pockets 35 near the base of the leaflets 26 is more likely to be
flushed away or effectively mixed with fresher incoming bodily
fluid on a continual basis.
[0033] It should be understood that the materials used to comprise
the support structure 11 can be selected from a well-known list of
suitable metals and polymeric materials appropriate for the
particular application, depending on necessary characteristics that
are required (self-expansion, high radial force, collapsibility,
etc.). The materials used for the valve structure 12 can comprise a
synthetic material or biologically-derived material appropriate for
the clinical application; however, investigational studies have
demonstrated that a bioremodelable material (such as an collagenous
extracellular matrix (e.g., small intestinal submucosa),
pericardial, or a growth factor-enhanced material may have superior
anti-thrombogenic properties within the body as the native cells
and tissue gradually replace the original leaflet material. The
number of leaflets possible for embodiments of the present
invention can be two, three, four, or any practical number, but
bi-leaflet valves may prove advantageous in low-flow venous
situation as compared to tri-leaflet embodiments, such the type
used as heart valves which are subject to high-flow situations
where thrombus formation is far less of a problem.
[0034] In the embodiments of FIGS. 2-8, the support structure 11 is
configured such that when the device is deployed within the bodily
passage 20, such as a vein of the lower legs or feet, an artificial
sinus 34 is formed adjacent to and surrounding the valve structure
12 such that the blood or other bodily fluids collecting within the
pockets 35 formed around the bases of the valve leaflets 26 is more
likely to be flushed out on a continual basis due to the
advantageous geometry created by the artificial sinus 34. The
principle is illustrated in the example of FIG. 1 which shows a
natural venous valve 21 in which retrograde blood 22 flowing or
falling back down and closing the valve is thought to create a
series of vortices 23 as it contacts the leaflets. It is believed
that the rounded shape of the enlarged natural sinus 37 surrounding
the valve 21 facilitates creation of these vortices, thereby
preventing blood from pooling or stagnating within the pockets 35
at the base of the valve 21, which may lead to thrombus formation
or other problems. The present invention, by virtue of the
configuration of the support structure 11, creates an artificial
sinus 34 that attempts to reproduce the function served by the
natural sinus 37 in the vein.
[0035] FIG. 2 depicts a side view of an illustrative embodiment of
the present invention in which the prosthesis 10 includes a first
or proximal section 15 and a second or distal section 17 that are
spaced apart from one another, defining an intermediate,
substantially open section 16 for creating the artificial sinus 34
in the vessel 20. The term `substantially open` is used herein to
define a largely unsupported portion of the bodily passage in which
at least some minimal interconnecting structure (e.g., thin or
flexible elements aligned with the leaflet commissures) is present
that traverses the unsupported portion of the bodily passage, but
it comprises very limited surface area and typically supplies
minimal, if any, force against the walls of the passageway lateral
to the valve structure 12. The proximal and distal sections 15,17,
which preferably comprise a pair of radially expandable or
self-expanding anchoring portions 24, are joined by an
interconnecting means 36, such as the illustrative pair of
connection struts 18,19 that allows the intermediate section 16 to
be otherwise open and free of scaffolding so that the vein walls 38
along that section of the vessel 20 are able to expand due to
pressure exerted by the blood flowing within the vein.
[0036] In the embodiments of the present invention, the anchoring
portions 24 may function as stents to help the bodily passage
remain patent, but their primary function is limited to engaging
the bodily passage to anchor the prosthesis thereagainst. The
support structure 11 and anchoring portions 24 also may be
configured to be readily collapsible as with a normal vein. Since
the diameters of the proximal and distal sections 15,17 generally
assume a fixed diameter after deployment, the intermediate section,
which is mostly unsupported or covered by structure, expands to
form a bulging region of the vessel that functions as an artificial
sinus 34. Although the interconnecting means 36 advantageously
permit the proximal and distal sections 15,17 to be deployed
together at a fixed distance from one another, it is within the
scope of the invention to have the valve prosthesis 10 comprise
separate unconnected sections that are deployed sequentially at an
effective distance from one another to create an artificial sinus
34 therebetween. Additionally, the interconnecting means 36 can
comprise suture, fabric, or some other non-rigid material to join
the proximal and distal sections 15,17 and define the optimal
length of the intermediate section 16, without interfering with the
creation of the artificial sinus 34. To deploy a prosthesis 10
having a flexible interconnecting means 36, one of either the
proximal or the distal sections 15,17 can be deployed first with
the delivery system then being slowly withdrawn until the
interconnecting means 36 becomes taut, whereby the opposite section
is then deployed.
[0037] In the illustrative embodiment, the valve structure 12
comprises a pair of leaflets 26 that are situated in the
intermediate section and attached to the proximal section 15 at two
commissural points 27,28, each located at the proximal ends of the
interconnecting struts 18,19, using an appropriate attachment means
30, such as suture, adhesive, fasteners, tissue welding using heat
and/or pressure, etc. The leaflets 26 are attached about their
distal ends 29 to the distal section 17 of the support structure 11
using the same or an other suitable attachment means 30. The valve
structure 12 is configured so that it advantageously expands with
the deployment of the proximal and distal sections 15,17 such that
the outer edges 39 thereof contact the vessel wall sufficiently to
at least substantially prevent leakage of bodily fluid around the
valve structure 12. Optionally, the wall-engaging outer edges of
the leaflets 26 can be reinforced with a separate frame 32 that is
attached to or incorporated into the outer edges 37 to improve
sealing with the vessel wall 38. An example of such a frame 32 is
depicted in embodiment shown in FIG. 3 in which the frame 32 also
serves as the interconnecting means 36 between the proximal and
distal section 15,17 of the support structure 11, with the struts
18,19 being laser cut from the same tube used to form the remainder
of the support structure 11. The valve frame 32 (that portion of
the support structure 11 that reinforces the valve structure 12)
can either be configured to exert relatively little radial force
beyond what might be required to ensure adequate contact with the
vessel wall 38, or it may be configured such that the frame 32
exerts sufficient radial force such that it assists in creating an
artificial sinus 34 in the portion of the vein along the
intermediate section 16 of the valve prosthesis 10.
[0038] Another method of creating the artificial sinus 34 is
depicted in FIGS. 4-5, whereby the support structure 11 includes an
expanded portion 31, larger in diameter than the remainder of the
support structure 11, that upon deployment, creates an artificial
sinus 34 surrounding the valve structure 12. The diameter of the
artificial sinus 34 caused extending the vessel wall 38 is, at its
widest point, preferably about 10-120% larger than the diameters of
the proximal and distal sections 15,17 when fully deployed
(unrestrained from within the delivery sheath), with a more
preferred differential of about 30-80% and a most preferred
difference of 50-70% larger, depending on the diameter of the vein,
the valve structure geometry, fluid column pressures at that
location, and other factors. In the illustrative embodiments, the
transition between the proximal and distal section 15,17 and the
expanded intermediate section 16 is curvilinear, creating a
bulge-like or flared configuration (FIGS. 4 and 5, respectively).
In the examples depicted, the support structure comprises a single
tubular anchoring portion 24 that is plastically, resiliently, or
otherwise deformed into a second configuration that includes the
expanded portion 31. For example, the anchoring portion 24 can be
laser cut from a tube of nitinol, placed around a mandril having
the desired shape, and heat set to produce the final desired shape.
In the embodiment of FIG. 4, the expanded portion 31 comprises the
intermediate section 16 of the prosthesis 10, such that the
artificial sinus 34 is created between the proximal and distal
sections 15,17 and the valve structure 12 is located therein. In
FIG. 5, the expanded portion 31, which comprises the proximal
section 15 of the support structure 11, includes a flared
configuration that extends outward from the distal section 17 (no
separately functional intermediate section 16 is present). The
valve structure 12 is attached about the proximal end 13, while the
flared, expanded portion 31 thereabout causes the vessel 20 to
bulge outward, thus creating an artificial sinus 34 about the
proximal end of the prosthesis 10. The artificial sinus 34
comprises a combination of a supported and an unsupported portion
in the embodiment of FIG. 5. In both illustrative embodiments the
valve structure 12 is sewn to the struts 33 of the support
structure within the passageway of the anchoring portion 24. Other
alternative methods of attachment include adhesives, staples or
other fasteners, wire, engagement barbs on the frame, tissue
welding, etc.
[0039] FIGS. 6-7 depict embodiments similar to that of FIG. 5,
except that the proximal, intermediate, and distal sections
15,16,17 comprise separate anchoring portions 24 (having a
serpentine or `zig-zag` configuration in the illustrative
embodiment) that are attached to one another in well-known manner,
such as by feeding the illustrative thread material 42 or suture
through the apices 45 of adjoining bends and securing it
therearound. In the embodiment of FIG. 6, the intermediate section
16 comprises a first and a second intermediate subsection 40,41 of
opposing frustoconical-shaped anchoring portion 24 that are coupled
to form the artificial sinus 34. The first and second subsections
40,41 can be manipulated into a frustoconical shape by plastically
deforming the anchoring portion 24 into that shape, or by
increasing constraint of the frame about the distal end of a
cylindrical-shaped proximal portion 15 and the proximal end of a
cylindrical-shaped distal portion 17 with a constraining means 42,
such as thread, suture, wire, band, covering, etc., so that the
respective sections 15,17 assume a frustoconical shape. Additional
constraining means 42 may be included at the first and second ends
13,14, as depicted, to maintain the cylindrical shape of the
proximal and distal 15,17 sections. The thread or suture 30
(constraining means) at the interface 46 interconnecting the first
and second intermediate subsections 40,41 may or may not function
to tension the apices 45 of those respective subsections. The
illustrative embodiment of FIG. 7 is similar to that of FIG. 6
except that the intermediate section 16 also comprises a third
intermediate subsection 43, located between intermediate subsection
40 and 41, that extends the length of the artificial sinus. The
illustrative third intermediate section 43 comprises a short
cylindrical or band-shaped portion whose width can be adjusted to
create the desired geometry of the artificial sinus 34. Additional
subsections can be added as well, if so desired.
[0040] FIG. 8 depicts an embodiment in which the support structure
11 comprises a proximal portion 15 joined to a distal portion 17 by
a interconnecting strut 36, the entire support structure being cut
from a single piece of cannula, such as stainless steel or nitinol.
The valve structure 12, comprising a plurality of leaflets 26, is
attached to the distal portion 17 such that the artificial sinus 34
is formed in the largely open, unsupported region between the
proximal and distal sections 15,17 by virtue of the vessel 20
bulging outward, as in the embodiment of FIG. 2. The valve
prosthesis 10 further includes an optional covering 44, such as an
outer sleeve of SIS (or other suitable biological or synthetic
material), that is attached to both the proximal and distal
sections 15,17 of the support structure 11, which helps seal the
prosthesis to prevent leakage of retrograde fluid therearound. The
covering 44 is preferably of a constitution and configuration such
that it does not interfere with the creation of the artificial
sinus 34.
[0041] FIGS. 9,11, and 13-20 comprise embodiments of an artificial
valve prosthesis 10 in which support structure 11 carrying the
leaflets 26 is configured to increase the leaflet contact
(coaptable) area 57 about the proximal portion of the valve
structure 12 without relying on built-in slack within the material
to bring the leaflets in closer proximity and provide for a
extensive sealing area, longitudinally. As defined in this
application, the leaflet contact area 57 comprises a longitudinal
portion along the valve structure 12 in which the facing surfaces
of opposing leaflets 26 (two or more) coapt or lie in close
proximity to one other while in a dry or resting, neutral state
(i.e., the pressure differentials across the valve orifice are
essentially equalized such that the leaflets are not being forced
together or apart due to external forces, such as fluid flow), when
the prosthesis is an expanded or deployed configuration. The
support frame 11 may be configured for maximizing the extent of the
leaflet contact area 57 by including one or more longitudinal
attachment struts 49,50 that define at least the proximal portion
75 of the attachment pathway 74 of each leaflet lateral outer edge
87,88 (the terms outer edge 39 and lateral outer edges 87,88 being
defined herein as the area or zone along the leaflet that comprises
the sealing interface). The longitudinal attachment struts
49,50/proximal attachment pathways 75 have a substantially
longitudinal orientation (e.g., substantially parallel) with
respect to the longitudinal axis 64 of the prosthesis (and valve
structure 12). At a point generally proximate the distal end 89 of
the leaflet contact area 57 (the proximal portion 96 of the
leaflet), the distal portions 76 of the adjacent attachment
pathways 74 (which are joined proximally about a commissural point)
diverge from one another (forming a generally Y-shaped pathway
configuration) and assume a much more circumferential orientation
than that of the proximal portion 75 of the pathway such that the
outer leaflet lateral edges 87,88 of each leaflet converge at a
point lateral to the free inner edge 84 thereof to seal the
passageway and form the distal portion 96 of the leaflet that
defines the bottom 96 or `floor` of the pocket 55 or intravascular
space adjacent the outer surfaces of each of the leaflets, which
generally assumes a strongly cupped or curved shape such that the
leaflet assumes a generally `folded` appearance due to the acutely
angled attachment pathway 74 with the proximal portion of the
leaflet having a strong longitudinal orientation with respect to
the prosthesis and vessel and the bottom portion 96 having a
strongly perpendicular orientation relative to the longitudinal
axis of the vessel and prosthesis. It should be noted that the
commissures 27,28, while located about the proximal end 13 of the
illustrative prosthesis 10, may be located proximal thereto such
that additional support structure 10 extends proximally, such as in
the embodiments of FIGS. 2-8,12.
[0042] By extending or maximizing the leaflet contact area and
decreasing the radius of the curvature of the leaflet (increasing
curvature) about the distal portion thereof, the basal or distal
portion of the pocket 35 adjacent each leaflet is enlarged to
facilitate and maximize the size and/or velocity of the flow
vortices 55,56 formed therein during retrograde flow. During
pre-clinical investigations, these broader pockets have been shown
to be especially advantageous in bi-leaflet artificial valve
designs implanted in the venous system, these valves exhibiting a
marked reduction in thrombus formation as compared to earlier
designs. The improvement in flow dynamics for the purpose of
clearing the pocket 35 of stagnant blood that can thrombose and
compromise valve function or lead to other complications is
depicted in a comparison of FIGS. 10 and 11. Laboratory analysis of
the patterns of retrograde flow within a valve has shown that
multiple vortices are typically created. In the embodiment of FIG.
10, which has a generally (inverted) V-shaped attachment pathway
74, a first vortex 55 is created below which a second, smaller
vortex 56 is usually present, usually having opposite flow, which
may be at least partially inadequate for clearing away blood
pooling about the base of the leaflets 60,61 in a venous valve. In
the embodiment of the present invention depicted in FIG. 11, which
has a generally (inverted) Y-shaped attachment pathway 74, the
larger pocket (at least at the basal portion) allows for a larger
and stronger second vortex 56 of fluid created by retrograde flow
that is more optimal for clearing away any pooling blood that would
otherwise collect there and potentially provide for greater
downforce on the leaflets 60,61 to improve closure of the
valve.
[0043] FIGS. 9 and 11 depict an artificial venous valve prosthesis
10 in which the frame 32 of the support structure 11 is configured
such that the pair of longitudinal attachment struts 49,50
extending from each of the commissures 27,28 that represent the
proximal attachment points for the valve structure (not shown) form
a first angle 47 (.alpha.) with respect to one another that is less
than the second angle 48 (.beta.) that is formed between the distal
attachment struts 51,52, which comprise continuations of the
longitudinal attachment struts 49,50 (together comprising the legs
58 of the frame 32), and the inside 63 of the vessel wall 38. The
first angle 47 is preferably between -10 and 30.degree. (a negative
angle being possible with a sufficiently large-radius bend about
the commissure) with a more preferred angle being 0-25.degree. and
a most preferred angle of 0-10.degree. The longitudinal attachment
struts 49,50 may both diverge and converge at various points
therealong (i.e., bow inward or outward), which in case, the first
angle may be relevant for only the proximal portion 75 or is
measurable between vectors representing the best straight line
longitudinally traversing each strut 49,50. The illustrative
embodiment also includes a pair of optional stabilizing arms 53,54
that extend laterally from the legs 58,59 to help center the
prosthesis 10 within the vessel 20. Ideally, the angles depicted in
the frame 32 configuration of FIG. 11 results in the opposing
leaflets 60,61 being much more in alignment (e.g., parallel) with
one another than in a prosthesis where the angles 47,48 are
relatively the same, such as the prior art valve shown in FIG. 10,
particularly over the proximal half of the leaflets 60,61. The
result is the creation of a larger pocket around the base of the
leaflets 60,61 that helps create larger and/or stronger vortices of
retrograde blood flow. A second clinical benefit is that there is a
larger area of coaptation between the leaflets 60,61, which helps
provide a better seal against possible reflux through the valve
orifice.
[0044] FIGS. 13-18 depict another group of embodiments configured
for maximizing the coaptation distance or region between the
leaflets in which the attachment pathway 74 comprises a proximal
portion 75 that generally extends along one or more longitudinal
attachment struts 49,50 that are generally aligned with the
longitudinal axis 64 of the prosthesis and a distal portion 76 that
is angled laterally from the longitudinal attachment struts and
generally follows the distal attachment struts 51,52 which unlike
the embodiment of FIG. 9, extend laterally outward from the
longitudinal struts 49,50 as separate struts. As with the
embodiment of FIG. 9, the distal attachment struts/portions
converge at a point oppositely facing each leaflet 60,61 where they
attach to the lateral support structure 53,54, which helps center
the prosthesis in the vessel and protects the leaflets from
adhering to the vessel wall. In the embodiments of FIGS. 13-17, the
support frame 11 further includes proximal support arms 77,78 that
attach to and extend from the longitudinal attachment struts 49,50
about the commissure points 27,28 and provide an interconnection
with the lateral support structure 53,54 (also shown in FIG.
15).
[0045] The embodiment depicted in FIGS. 13-14 comprises a pair of
longitudinal attachment struts 49,50, generally parallel to one
another, which are adapted for attaching the respective leaflets 26
therealong, thus creating a large leaflet contact or coaptable area
57 that extends over half of the length of the prosthesis. As
depicted in FIG. 16, The lateral support structure 53,54 shares or
mirrors the configuration of the longitudinal attachment strut
regions which they interconnect, except that they are located
90.degree. therefrom and oriented oppositely thereto, such that the
support structure 11 generally forms a serpentine configuration
adapted to be readily collapsible and expandable. In the
illustrative embodiment, the support structure 11 or frame can be
divided into four sections or quadrants 70,71,72,73 that are
identical except for their orientation, sections 70 and 72 being
oriented with the commissures 27,28 and longitudinal attachment
struts 49,50 carrying the valve structure 12 being oriented
proximally toward the first end 13 of the prosthesis 10. The
repeating, uniform design of the support structure 11 of the
illustrative embodiment advantageously provides better structural
stability, compressibility/expandability, and overall integrity
than a support structure that does that comprise a non-uniform,
non-repeating frame pattern.
[0046] The lateral arms 77,78 of the lateral support structure
53,54, that connect to the longitudinal attachment struts 49,50
each include a strut 68 that carries a proximal radiopaque marker
67 used to facilitate orientation of the device 10 and provide
additional support. An identical distal strut 90 and an optional
radiopaque marker 91 is located distal to the longitudinal
attachment struts 49,50 and attached to the distal attachment
struts 51,52 to serve a similar orientation and stabilization
function. An integral barb 25 is located about the commissural
bends 27,28 that interconnect the longitudinal attachment struts
49,50. The parallel longitudinal attachment struts 49,50 are also
interconnected about their distal ends by a short interconnecting
strut 81 such that an elongate closed cell 92 is formed. The width
of cell 92 is not critical, although it may be made sufficiently
narrow such that it serves to further pin or anchor the leaflets
60,61 to the struts 49,50, which could be especially advantageous
in fixation if the leaflet material retracts during the remodeling
process. A preferred width between the two struts 49,50 would be
between 0-5 mm, with 0-3 mm being more preferred and 0-1 mm being
most preferred. If the spacing is too wide, gaps may be created
between the opposing leaflets which could allow for an unacceptable
amount of reflux through the valve.
[0047] A similar frame design is shown in FIG. 17 which includes a
single longitudinal attachment strut 49 to which both leaflets
60,61 are sewn or otherwise attached allowing for similar extended
coaptation between leaflets. The leaflets 60,61 can be attached
such that each abuts the strut 49 (and sewn or attached without
being wrapped over the strut) or the first lateral leaflet edge
(not shown) is wrapped around the strut 49 while the second leaflet
lateral edge of the opposite leaflet is sewn over the first lateral
leaflet edge and strut 49. The single attachment strut can be of a
width that is generally uniform with respect to the other support
structure or it may be made substantially thicker, such as shown in
FIG. 19. Furthermore, a thicker strut 49 could include apertures 93
or slots of any shape or length distributed therealong for
receiving sutures or other attachment elements 30, such as clips,
rings, etc., for affixing or anchoring the leaf outer edges
thereto. FIG. 20 depicts an embodiment having a pair of
longitudinal attachment struts 49,50 with anchoring structure 95,
such as the illustrative scalloped edge that is strategically
configured therealong to help prevent or limit the attachment
element 97 and the valve structure itself, from sliding down the
longitudinal attachment struts 49,50, especially during any
retraction that may occur with a bioremodelable material. The
anchoring structure can comprise any projections or other structure
that provides a shoulder or irregularities along the edges of the
struts that helps limit sliding of the leaflets along the
longitudinal attachment struts 49,50. Further examples of
adaptations for limiting movement or migration of attachment
elements (e.g., sutures) and covering material are disclosed in an
application to Case et al. (U.S. Ser. No. 10/820,918), entitled
`Intraluminal Support Device with Graft` and filed Apr. 8, 2004,
which is expressly incorporated by reference herein.
[0048] FIG. 18 depicts an embodiment having generally, but not
absolutely parallel longitudinal attachment struts 49,50 which
slightly converge toward the distal end 14 of the prosthesis 10
(and are spaced more distant from each other than the embodiment of
FIGS. 13-14. The commissural bends 27,28 and distal bends 82
interconnect the longitudinal attachment struts and form a closed
cell 92 as in the embodiment of FIGS. 13-16. The distal attachment
struts 51,52 provide the interconnection between the opposite
closed cells 92 as well as the distal portion 76 of the attachment
pathway 74. They also carry a lateral arm 93 and together comprise
the lateral support structure 83,84 that provide longitudinal
support/stabilization and leaflet protection. The embodiment of
FIG. 18 lacks proximal support arms 77,78 of the embodiment of
FIGS. 13-16.
[0049] The illustrative support structure 11 in FIGS. 9, 11, 13-18
is not critical to achieve the optimal leaflet angles in the valve
structure 12 for creating larger pockets, as depicted. For example,
the attachment pathway 74 of the valve structure 12 can comprise an
attachment to an outside support frame to form the illustrative
configuration with the frame 32 that is not necessarily extending
along the outer edges 39 of the leaflets 60,61, but rather attached
to selected strut that cross the attachment pathway 74, especially
along the distal portion 76 of the pathway. Furthermore, at least a
portion of the outer edges 39 can be directly affixed to the vessel
wall (such as being sutured, heat welded, or anchored with barbs,
adhesives, etc.) with the frame 11 being absent or reinforcing or
shaping only a limited portion of the leaflet outer edges 39, thus
allowing for the vein to naturally collapse (at least partially)
when not filled with blood. In the example depicted in FIG. 21, the
frame 11 comprises a partial support 98 of a hair-pin configuration
that includes a proximal bend about each commissure 27,28 with
free-ended longitudinal attachment struts 49,50 extending therefrom
which help form the leaflet angle 47, while the distal portion 76
of the attachment pathway 74 comprises an alternative attachment
that does not result in the leaflet material being urged
thereagainst by a radially expandable frame. Methods include
surgical attachment, tissue welding, adhesives, barbs and other
well-known methods, teachings of which is included in a co-pending
U.S. patent application entitled, `Percutaneously Deployed Vascular
Valves with Wall-Adherent Adaptations (Case et al.) filed Apr. 1,
2004 (Ser. No. to be added by amendment), the disclosure of which
is expressly incorporated by reference herein. The angle of the
leaflets 60,61 relative to the longitudinal axis 64 of the
prosthesis and vessel (half of the first angle 47 or .alpha./2) is
preferably -5-15.degree. with a more preferred angle of
0-10.degree. and a most preferred angle of 0-5.degree. The
relatively small or shallow angles of the longitudinal attachment
struts 49,50 about the commissures 27,28 allows for a larger space
adjacent the leaflets 60,61 and broader pockets 35 at the base of
the leaflets. The longitudinal attachment struts 49,50 of the
support structure can be formed generally parallel to one another
along the proximal portions of the longitudinal attachment struts
49,50 to create the maximum pocket size and greater coaptation of
the leaflets. For example, the pocket 35 areas would be maximized
in an attachment pathway 74 where angle 47 is zero (or a negative
angle) and angle 48 is at least 90.degree., such that the
attachment pathway along each leaflet lateral outer edge 87,88 is
generally L-shaped such that the distal portion 76 of the
attachment pathway angles abruptly from the proximal portion rather
than assuming a dog-leg configuration as shown in the illustrative
embodiments.
[0050] The amount of contactable or coaptable area 57 can be
expressed in different ways. In the present invention, the length
of the leaflet contact area 57 (or proximal portion 75 of the
attachment pathway) in a typical venous valve prosthesis is
preferably at least 2 mm and as much as 50 mm (depending on the
configuration of the valve prosthesis), with a more preferred
length of 5-30 mm and a most preferred range of 5-15 mm. In an
average sized venous valve having a length of 25 mm, the preferred
range of the leaflet contact area 57 or proximal attachment pathway
75 would be 10-80% of the prosthesis length (2.5-20 mm), assuming
the valve structure 12 is generally as long as the support frame
11. A more preferred leaflet contact area 57 would comprise 30-60%
with 35-55% being most preferred in a prosthesis of the same
general type as depicted. The relationship between leaf contact
area and the diameter of the vessel may be a factor in optimizing
the functionality of the valve prosthesis 10. Preferably, the
length of the longitudinal attachment struts 49,50 and/or leaflet
contact area 57 is 25 to 250% of the nominal vessel diameter with a
more preferred range of 25-150%.
[0051] The amount of slack in the leaflet material also helps
determine how well the leaflets coapt during retrograde flow and
how large of an opening they permit during antegrade flow.
Preferably, but not essentially, the prosthesis is configured such
that the distance formed between the leaflets in their fully open
position and the vessel diameter remains preferably between 0-100%
of the vessel diameter, with a more preferred range of 20-80% of
the vessel diameter and a most preferred range of 50-70%. By
substantially orienting the longitudinal attachment struts 49,50
with the longitudinal axis 64 of the prosthesis, less slack is
necessary for optimal or extended coaptation. Not having the
leaflets regularly contact the outer walls of the vessel can be
especially important when using a bioremodelable material, such as
an ECM, which can partially or completely adhere to the wall over
time as tissue grows into the leaflets, thus compromising the
functionality of the valve.
[0052] FIG. 12 depicts an embodiment having different structural
configuration to after retrograde fluid flow patterns within the
pocket to prevent pooling of blood or bodily fluid. The support
structure 11 includes proximal and distal sections 15,17 which are
sized and configured to expand and engage the walls 38 when the
valve prosthesis 10 is deployed within the bodily passage 20. The
intermediate section 16, which includes the valve structure 12, is
narrower than each of the adjoining proximal and distal sections
15,17. A covering of biologically-derived or synthetic
biocompatible or bioremodelable material 44, such as a collagenous
extracellular matrix (ECM) (e.g., SIS), pericardial tissue, or
fabric, such as DACRON, ePTFE, etc., is attached over or inside the
support structure to enclose passageway 62 and to help seal the
prosthesis with the vessel. The proximal and distal sections 15,17
are generally frustoconical or bowl-shaped with the interface 46
with the proximal or distal end of the intermediate section 16
being smaller in diameter than the proximal or distal ends 13,14 of
the prosthesis. By narrowing the passageway 62 of the prosthesis 10
at the point where it transitions between the proximal section 15
and the intermediate section 17, a Venturi effect is created in
which the retrograde flow is accelerate, which advantageously
produces enhanced flushing action (e.g., stronger vortices) within
the pockets 35 surrounding the leaflets 60,61. The ability of the
valve prosthesis 10 to prevent pooling of blood or fluid around the
pockets 35 is further enhanced in the illustrative embodiment by
configuring the leaflets 61,62 as in the example shown in FIG. 11.
It is not necessary to the invention that the proximal and distal
sections share the same configuration. The respective sections
15,16,17 may be separate, attached units, as shown, or represent
subsections of a single anchoring portion 24, similar to the
embodiment of FIG. 4.
[0053] It should be noted that the support structure and valve
structure shown in each of the figures in the application are
merely exemplary of the numerous well-known possibilities, many
others of which are disclosed in U.S. patent application Ser. No.
10/642,372 entitled, `Implantable Vascular Device,` filed Aug. 15,
2003 and whose disclosure is expressly incorporated by reference
herein. For example, the valve structure may comprise more than the
illustrative two leaflets or comprise leaflets of other shapes and
configuration. The valve structure may also comprise a non-leaflet
valve such as one or more tubular sleeves or other configurations
adapted to restrict fluid flow. With regard to the support
structure, it may be formed from wire, cut from a section of
cannula, molded or fabricated from a polymer, biomaterial, or
composite material, or a combination thereof. The pattern (i.e.,
configuration of struts and cells) of the anchoring portion(s) that
is selected to provide radial expandability to the prosthesis is
also not critical for an understanding of the invention. Any other
undisclosed or incidental details of the construction or
composition of the various elements of the disclosed embodiment of
the present invention are not believed to be critical to the
achievement of the advantages of the present invention, so long as
the elements possess the attributes needed for them to perform as
disclosed. The selection of these and other details of construction
are believed to be well within the ability of one of even
rudimentary skills in this area, in view of the present disclosure.
Illustrative embodiments of the present invention have been
described in considerable detail for the purpose of disclosing a
practical, operative structure whereby the invention may be
practiced advantageously. The designs described herein are intended
to be exemplary only. The novel characteristics of the invention
may be incorporated in other structural forms without departing
from the spirit and scope of the invention. The invention
encompasses embodiments both comprising and consisting of the
elements described with reference to the illustrative embodiments.
Unless otherwise indicated, all ordinary words and terms used
herein shall take their customary meaning as defined in The New
Shorter Oxford English Dictionary, 1993 edition. All technical
terms shall take on their customary meaning as established by the
appropriate technical discipline utilized by those normally skilled
in that particular art area. All medical terms shall take their
meaning as defined by Stedman's Medical Dictionary, 27.sup.th
edition.
* * * * *