U.S. patent application number 10/143810 was filed with the patent office on 2002-12-05 for mechanical heart valve.
This patent application is currently assigned to Triflo Medical, Inc.. Invention is credited to Lapeyre, Didier, Steinseifer, Ulrich.
Application Number | 20020183840 10/143810 |
Document ID | / |
Family ID | 22209859 |
Filed Date | 2002-12-05 |
United States Patent
Application |
20020183840 |
Kind Code |
A1 |
Lapeyre, Didier ; et
al. |
December 5, 2002 |
Mechanical heart valve
Abstract
The present invention relates to an improved trileaflet
mechanical heart valve 100 and an improved leaflet 110 for use with
such valve. The valve 100 and leaflet 110 of the present invention
provide improved flow characteristics, minimize blood clotting
behind the leaflets, and provide more natural opening and closing
times. The valve includes a valve housing 105 which contains
pivot/hinge mechanism (130, 200, and 300) for allowing rotation of
and retention of the leaflets 110. The valve housing 105 also
includes windows or openings 125 which allows for complete washing
of the pivot/hinge mechanism (130, 200, and 300) as well as the
leaflets 110. The novel leaflets 110 are airfoil-like having a
complex S-shaped curvature on their outer surface. This novel
geometry, when combined with the location of the leaflet's pivot
axis, causes a tendency for the leaflet 110 to rotate towards the
closed position. Thus, the leaflet 110 begins to close much earlier
than a conventional leaflet and is substantially closed before the
flow reverses, similar to the function of a natural valve.
Inventors: |
Lapeyre, Didier; (Pacy Sur
Eure, FR) ; Steinseifer, Ulrich; (Aachen,
DE) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Assignee: |
Triflo Medical, Inc.
|
Family ID: |
22209859 |
Appl. No.: |
10/143810 |
Filed: |
May 14, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10143810 |
May 14, 2002 |
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09323402 |
Jun 1, 1999 |
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6395024 |
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60088184 |
Jun 5, 1998 |
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Current U.S.
Class: |
623/2.22 |
Current CPC
Class: |
A61F 2250/0036 20130101;
A61F 2/2403 20130101 |
Class at
Publication: |
623/2.22 |
International
Class: |
A61F 002/24 |
Claims
We claim:
1. A rotatable leaflet for a prosthetic heart valve comprising: a
main portion including leading and trailing edge surfaces, and
inner and outer surfaces connecting the leading and trailing edge
surfaces, wherein the inner surface generally defines a convex
curvature from the leading edge surface to the trailing edge
surface and the outer surface generally defines a convex curvature
proximate the leading edge surface and a concave curvature
proximate the trailing edge surface; and first and second winglet
portions situated on opposite ends of the leaflet to facilitate
rotation of the leaflet.
2. The rotatable leaflet of claim 1, wherein the inner surface has
a convex curvature from the first winglet portion to the second
winglet portion.
3. The rotatable leaflet of claim 1, wherein the outer surface has
a concave curvature from the first winglet portion to the second
winglet portion.
4. The rotatable leaflet of claim 1, 2, or 3, wherein the distance
between the inner and outer surfaces is greater proximate the
leading edge surface than the distance between the inner and outer
surfaces proximate the trailing edge surface such that the leaflet
has an airfoil-like cross section.
5. The rotatable leaflet of claim 1, wherein the leaflet is formed
from pyrolytic carbon.
6. The rotatable leaflet of claim 4, wherein the leaflet is formed
from pyrolytic carbon.
7. The rotatable leaflet of claim 1, wherein each winglet portion
is attached to the inner and outer surfaces and the leading and
trailing edge surfaces.
8. A rotatable leaflet for an early-closing prosthetic heart valve
comprising: a main portion including leading and trailing edge
surfaces, and inner and outer surfaces connecting the leading and
trailing edge surfaces; first and second winglet portions situated
on opposite ends of the leaflet to facilitate rotation of the
leaflet; and closure means for causing the leaflet to rotate toward
a closed position prior to substantial backwards flow of blood
through the heart valve.
9. The rotatable leaflet of claim 8, wherein the closure means
causes the leaflet to begin to rotate toward a closed position
about when the maximum flow rate has been achieved through the
valve.
10. The rotatable leaflet of claim 8, wherein the closure means
comprises a configuration wherein the inner surface has a convex
curvature from the leading edge surface to the trailing edge
surface and the outer surface has a convex curvature proximate the
leading edge surface and a concave curvature proximate the trailing
edge surface.
11. The rotatable leaflet of claim 10, wherein the closure means
further comprises a configuration wherein the distance between the
inner and outer surfaces is greater proximate the leading edge
surface than the distance between the inner and outer surfaces
proximate the trailing edge surface such that the leaflet has an
airfoil-like cross section.
12. The rotatable leaflet of claim 10, wherein the inner surface
has a convex curvature from the first winglet portion to the second
winglet portion.
13. The rotatable leaflet of claim 12, wherein the outer surface
has a concave curvature from the first winglet portion to the
second winglet portion.
14. The rotatable leaflet of claim 8 or 11, wherein the leaflet is
formed from pyrolytic carbon.
15. A mechanical prosthetic heart valve, the valve comprising: an
annular housing having an inner circumferential surface: and at
least one leaflet disposed adjacent to the inner circumferential
surface and capable of rotation between an open position in which
blood can flow through the heart valve and a closed position in
which blood is prevented from flowing through the heart valve, the
leaflet comprising: a main portion including leading and trailing
edge surfaces, and inner and outer surfaces connecting the leading
and trailing edge surfaces, wherein the inner surface generally
defines a convex curvature from the leading edge surface to the
trailing edge surface and the outer surface generally defines a
convex curvature proximate the leading edge surface and a concave
curvature proximate the trailing edge surface; and first and second
winglet portions situated on opposite ends of the leaflet to
facilitate rotation of the leaflet.
16. The mechanical prosthetic heart valve of claim 15, wherein the
annular housing comprises a nozzle shape along the inner
circumferential surface.
17. The mechanical prosthetic heart valve of claim 15, wherein the
inner circumferential surface includes inflow projections to
receive the leaflet.
18. The mechanical prosthetic heart valve of claim 15, wherein the
inner surface of the at least one leaflet has a convex curvature
from the first winglet portion to the second winglet portion.
19. The mechanical prosthetic heart valve of claim 18, wherein the
outer surface of the at least one leaflet has a concave curvature
from the first winglet portion to the second winglet portion.
20. The mechanical prosthetic heart valve of claim 15, 18 or 19,
wherein the distance between the inner and outer surfaces of the at
least one leaflet is greater proximate the leading edge surface
than the distance between the inner and outer surfaces proximate
the trailing edge surface such that the at least one leaflet has an
airfoil-like cross section.
21. The mechanical prosthetic heart valve of claim 15, further
comprising at least two leaflets.
22. The mechanical prosthetic heart valve of claim 21, further
comprising at least three leaflets.
23. The mechanical prosthetic heart valve of claim 15, wherein the
valve housing is formed from a metallic material.
24. The mechanical prosthetic heart valve of claim 15, wherein the
at least one leaflet is formed from pyrolytic carbon.
25. A mechanical early-closing prosthetic heart valve, the valve
comprising: an annular housing having an inner circumferential
surface: and at least one leaflet disposed adjacent to the inner
circumferential surface and capable of rotation between an open
position in which blood can flow through the heart valve and a
closed position in which blood is prevented from flowing through
the heart valve, the leaflet comprising closure means for causing
the leaflet to rotate toward a closed position prior to substantial
back flow of blood through the heart valve.
26. The mechanical early-closing prosthetic heart valve of claim
25, wherein the closure means causes the leaflet to begin to rotate
toward a closed position about when a maximum flow rate has been
achieved through the valve.
27. The mechanical early-closing prosthetic heart valve of claim
25, wherein the at least one leaflet comprises: a main portion
including leading and trailing edge surfaces, and inner and outer
surfaces connecting the leading and trailing edge surfaces; and
first and second winglet portions situated on opposite ends of the
at least one leaflet to facilitate rotation of the leaflet.
28. The mechanical early-closing prosthetic heart valve of claim
27, wherein the closure means comprises a configuration wherein the
inner surface generally defines a convex curvature from the leading
edge surface to the trailing edge surface and the outer surface
generally defines a convex curvature proximate the leading edge
surface and a concave curvature proximate the trailing edge
surface.
29. The mechanical early-closing prosthetic heart valve of claim
28, wherein the closure means further comprises a configuration
wherein the distance between the inner and outer surfaces of the at
least one leaflet is greater proximate the leading edge surface
than the distance between the inner and outer surfaces proximate
the trailing edge surface such that the leaflet has an airfoil-like
cross section.
30. A mechanical prosthetic heart valve comprising: an annular
housing having an inner circumferential surface; and at least one
leaflet disposed adjacent to the inner circumferential surface and
capable of rotation between an open position in which blood can
flow through the heart valve and a closed position in which blood
is prevented from flowing through the heart valve, the at least one
leaflet comprising a main portion including leading and trailing
edge surfaces, and inner and outer surfaces connecting the leading
and trailing edge surfaces, and first and second winglet portions
situated on opposite ends of the at least one leaflet to facilitate
rotation of the at least one leaflet; and first and second leaflet
pivot structures adapted to cooperate with the first and second
winglets, respectively, to facilitate rotation of the at least one
leaflet between the open and closed positions, each of the first
and second leaflet pivot structures comprising: an inflow
projection extending from the inner circumferential surface of the
housing and adapted to contact one of the winglet portions in one
of the open and closed positions; and a closing projection
extending from the inner circumferential surface of the housing and
adapted to contact one of the winglet portions in the closed
position, wherein the closing projection and the inflow projection
are configured and spaced from one another to increase flow
velocity proximate the one of the winglet portions.
31. The mechanical prosthetic heart valve of claim 30, wherein each
inflow projection has a first width proximate the inner surface of
the annular housing, and a second width distal from the inner
surface of the valve housing less than the first width.
32. The mechanical prosthetic heart valve of claim 30, wherein each
closing projection has a first width proximate the inner surface of
the annular housing, and a second width distal from the inner
surface of the valve housing less than the first width.
33. The mechanical prosthetic heart valve of claim 30, wherein the
annular housing defines at least one opening therethrough proximate
the inflow and closing projections.
34. The mechanical prosthetic heart valve of claim 33, wherein the
distance between the inflow projection and the closing projection
decreases in the blood flow direction to direct at least a portion
of the blood flow through the at least one opening when the at
least one leaflet is in the open position.
35. The mechanical prosthetic heart valve of claim 30, wherein the
inner surface of the at least one leaflet generally defines a
convex curvature from the leading edge surface to the trailing edge
surface and the outer surface of the at least one leaflet generally
defines a convex curvature proximate the leading edge surface and a
concave curvature proximate the trailing edge surface.
36. The mechanical prosthetic heart valve of claim 35, wherein the
distance between the inner and outer surfaces is greater proximate
the leading edge surface than the distance between the inner and
outer surfaces proximate the trailing edge surface such that the at
least one leaflet has an airfoil-like cross section.
37. A mechanical prosthetic heart valve comprising: an annular
housing having an inner circumferential surface and defining at
least one opening through the circumferential surface; and at least
one leaflet disposed adjacent to the inner circumferential surface
and capable of rotation between an open position in which blood can
flow through the heart valve and a closed position in which blood
is prevented from flowing through the heart valve, the at least one
leaflet comprising a main portion and first and second winglet
portions situated on opposite ends of the leaflet to facilitate
rotation of the leaflet, wherein no portion of the at least one
leaflet is received within the at least one opening during rotation
between the open and the closed position to provide for increased
blood flow proximate to one of the winglet portions.
38. The mechanical prosthetic heart valve of claim 37, wherein the
annular valve housing includes first and second leaflet pivot
structures adapted to cooperate with the first and second winglet
portions, respectively, to facilitate rotation of the at least one
leaflet between the open and closed positions, each of the first
and second leaflet pivot structures comprising: an inflow
projection extending from the inner circumferential surface of the
housing and adapted to contact one of the winglet portions in one
of the open and closed positions; and a closing projection
extending from the inner circumferential surface of the housing and
adapted to contact one of the winglet portions in the closed
position, wherein the closing projection and the inflow projection
are configured and spaced from one another to direct flow through
the at least one opening through the circumferential surface.
39. The mechanical prosthetic heart valve of claim 37, wherein the
main portion of the at least one leaflet includes leading and
trailing edge surfaces, and inner and outer surfaces connecting the
leading and trailing edge surfaces, and wherein the inner surface
generally defines a convex curvature from the leading edge surface
to the trailing edge surface and the outer surface generally
defines a convex curvature proximate the leading edge surface and a
concave curvature proximate the trailing edge surface.
40. The mechanical prosthetic heart valve of claim 39, wherein the
distance between the inner and outer surfaces is greater proximate
the leading edge surface than the distance between the inner and
outer surfaces proximate the trailing edge surface such that the at
least one leaflet has an airfoil cross section.
41. The mechanical prosthetic heart valve of claim 38, wherein the
at least one opening through the circumferential surface is
proximate the opening and closing projections.
42. The mechanical prosthetic heart valve of claim 37, wherein the
annular valve housing is formed from a metallic material.
43. The mechanical prosthetic heart valve of claim 37, wherein the
at least one leaflet is formed from pyrolytic carbon.
44. A mechanical early-closing prosthetic heart valve, the valve
comprising: an annular housing having an inner circumferential
surface; and at least one leaflet disposed adjacent to the inner
circumferential surface and capable of rotation between an open
position in which blood can flow through the heart valve and a
closed position in which blood is prevented from flowing through
the heart valve, the at least one leaflet comprising an
early-closure means for creating a tendency for the leaflet to
rotate toward the closed position such that the leaflet is
substantially closed prior to the initiation of back flow of blood
through the heart valve.
45. The mechanical early-closing prosthetic heart valve of claim
44, whereby the at least one leaflet is more than 50% closed prior
to the initiation of back flow of blood through the heart
valve.
46. The mechanical early-closing prosthetic heart valve of claim
45, whereby the at least one leaflet is more than 60% closed prior
to the initiation of back flow of blood through the heart
valve.
47. The mechanical early-closing prosthetic heart valve of claim
46, whereby the at least one leaflet is more than 70% closed prior
to the initiation of back flow of blood through the heart
valve.
48. The mechanical early-closing prosthetic heart valve of claim
47, whereby the at least one leaflet is more than 80% closed prior
to the initiation of back flow of blood through the heart
valve.
49. The mechanical early-closing prosthetic heart valve of claim
48, whereby the at least one leaflet is more than 90% closed prior
to the initiation of back flow of blood through the heart
valve.
50. The mechanical early-closing prosthetic heart valve of claim
46, wherein the at least one leaflet further comprises: a main
portion including leading and trailing edge surfaces, and inner and
outer surfaces connecting the leading and trailing edge surfaces;
and . first and second winglet portions situated on opposite ends
of the at least one leaflet to facilitate rotation of the at least
one leaflet, each of the winglet portions having a first side
proximate the annular valve housing and a second side opposite
thereto.
51. The mechanical early-closing prosthetic heart valve of claim
50, wherein the early-closure means comprises a configuration
wherein the inner surface of the at least one leaflet has a convex
curvature from the leading edge surface to the trailing edge
surface and the outer surface has a convex curvature proximate the
leading edge surface and a concave curvature proximate the trailing
edge surface.
52. The mechanical early-closing prosthetic heart valve of claim
51, wherein the early-closure means comprises a configuration
wherein the distance between the inner and outer surfaces of the at
least one leaflet is greater proximate the leading edge surface
than the distance between the inner and outer surfaces proximate
the trailing edge surface such that the at least one leaflet has an
airfoil cross section.
53. The mechanical early-closing prosthetic heart valve of claim
50, wherein at least one opening through the annular housing is
provided to allow blood flow across the first side of at least one
of the winglet portions when the at least one leaflet is in the
open position.
54. A mechanical early-closing prosthetic heart valve, the valve
comprising: an annular housing having an inner circumferential
surface; and at least one leaflet disposed adjacent to the inner
circumferential surface and capable of rotation between an open
position in which blood can flow through the heart valve and a
closed position in which blood is prevented from flowing through
the heart valve, the at least one leaflet comprising surfaces with
complex curvatures for creating a tendency for the at least one
leaflet to rotate toward the closed position such that the at least
one leaflet is substantially closed prior to the initiation of back
flow of blood through the heart valve.
55. The mechanical early-closing prosthetic heart valve of claim
54, wherein the surfaces with complex curvatures causes the at
least one leaflet to begin to rotate toward a closed position about
when a maximum flow rate has been achieved through the valve.
56. The mechanical early-closing prosthetic heart valve of claim
54, wherein the at least one leaflet further comprises: a main
portion including leading and trailing edge surfaces, and inner and
outer surfaces connecting the leading and trailing edge surfaces;
and. first and second winglet portions situated on opposite ends of
the at least one leaflet to facilitate rotation of the at least one
leaflet, each of the winglet portions having a first side proximate
the annular valve housing and a second side opposite thereto.
57. The mechanical early-closing prosthetic heart valve of claim
56, wherein the complex curvatures comprise a configuration wherein
the inner surface of the at least one leaflet has a convex
curvature from the leading edge surface to the trailing edge
surface and the outer surface has a convex curvature proximate the
leading edge surface and a concave curvature proximate the trailing
edge surface.
58. The mechanical early-closing prosthetic heart valve of claim
57, wherein the complex curvatures comprise a configuration wherein
the distance between the inner and outer surfaces of the at least
one leaflet is greater proximate the leading edge surface than the
distance between the inner and outer surfaces proximate the
trailing edge surface such that the at least one leaflet has an
airfoil cross section.
59. The mechanical early-closing prosthetic heart valve of claim
56, wherein at least one opening through the inner circumferential
surface is provided to allow blood flow across the first side of at
least one of the winglet portions when the at least one leaflet is
in the open position.
Description
BACKGROUND OF THE INVENTION
[0001] Continuing Data
[0002] This application claims priority under 35 U.S.C. .sctn.
19(e) to U.S. Provisional Application No. 60/088,184, filed Jun. 5,
1998, and under 35 U.S.C. .sctn.120 to U.S. Ser. No. 09/035,981
entitled MECHANICAL VALVE PROSTHESIS WITH OPTIMIZED CLOSING MODE,
filed Mar. 6, 1998, whose disclosure is expressly incorporated by
reference herein, and to its parent application, U.S. Ser. No.
08/859,530, filed May 20, 1997, now abandoned.
FIELD OF INVENTION
[0003] The present invention relates to an improved trileaflet
mechanical heart valve. More specifically, the present invention
relates to a trileaflet mechanical heart valve with improved flow
characteristics. Such a mechanical heart valve is useful for
surgical implantation into a patient as a replacement for a damaged
or diseased heart valve.
BACKGROUND CONSIDERATIONS
[0004] There are numerous considerations in the design and
manufacture of a mechanical prosthetic heart valve. An important
consideration is the biocompatibility of the materials used in the
prosthesis. The materials used must be compatible with the body and
the blood. Furthermore, the materials must be inert with respect to
natural coagulation processes of the blood, i.e., they must not
induce thrombosis (an aggregation of blood factors, primarily
platelets and fibrin with entrapment of cellular elements,
frequently causing vascular obstruction at the point of its
formation) when contacted by the blood flow. A local thrombus can
give rise to an embolism (the sudden blocking of a blood carrying
vessel) and can even under certain circumstances hinder proper
valve operation. Numerous materials have been tested for such
desirable biocompatibility. Several materials are commonly used for
making commercially available prosthetic heart valves (materials
such as stainless steel, chromium alloys, titanium and its alloys,
and pyrolytic carbon).
[0005] Another consideration in the design and manufacture of a
mechanical prosthetic heart valve is the valve's ability to provide
optimum fluid flow performance. Mechanical prosthetic heart valves
often create zones of turbulent flow, eddies, and zones of
stagnation. All of these phenomena can also give rise to thrombosis
and thrombo-embolisms. Biological valves (or bioprostheses) emulate
the form and the flow pattern of the natural heart valve and thus
have better fluid flow performance over conventional mechanical
prostheses. Such bioprosthetic valves do not require long-term
anti-coagulant medication to be taken by the patient after
implantation at least in the aortic position. These two
thrombus-generating factors (materials used and flow
characteristics) are problematic in conventional mechanical heart
valve prostheses. Thus, patients who currently receive a mechanical
heart valve prosthesis require a continuous regime of
anti-coagulant drugs which can result in bleeding problems. The use
of anti-coagulant drugs therefore constitutes a major drawback of
mechanical heart valve prostheses when compared with
bioprostheses.
[0006] However, biological replacement valves suffer from problems
too. As clinical experience has indicated, unlike mechanical
valves, their life-span of is often too short. Because of the
progressive deterioration of bioprostheses, they often need to be
replaced via costly additional major surgery.
[0007] Yet another consideration in the design and manufacture of a
mechanical prosthetic heart valve concerns the head loss (pressure
drop) associated with the valve. This head loss occurs during the
systolic ejection or diastolic filling of a ventricle. In
conventional designs, some head loss is inevitable since it is
inherent to the reduction in the effective orifice area of the
mechanical prosthetic heart valve as compared to natural valves.
The reduction in effective orifice is caused by the sewing ring
which is conventionally required for surgical installation of the
prosthetic valve, by the thickness of the valve housing, and by the
hinges which enable the valve's flaps (leaflets) to move between an
open and closed position. Another portion of the head loss is due
to the geometric disposition of the valve's flaps with respect to
the flow of blood.
[0008] As mentioned above with respect to the progressive
deterioration of bioprostheses, durability is another consideration
in the design and manufacture of a mechanical prosthetic heart
valve. A mechanical prosthetic heart valve should demonstrate a
mechanical lifetime equivalent to approximately 380-600 million
cycles (i.e., the equivalent of about 15 years). Obviously, the
mechanical lifetime is related to the geometrical design of the
valve as well as the mechanical characteristics of the materials
used.
[0009] Of course, the valve's ability to minimize leakage is also
important. Leakage generally comprises regurgitation (backward flow
of blood through the valve during operation, and otherwise known as
dynamic leakage) and static leakage (any flow through the valve in
the fully closed position). In the conventional valves, the amount
of regurgitation is at least 5% of the volume of blood flow during
each cycle, and is often more. When a patient has two prosthetic
valves on the same ventricle, regurgitation (dynamic leakage) thus
comprises at least about 10% (leakage on the order of several
hundred L per day). Thus, dynamic leakage clearly puts undesirable
stress on the heart muscle. Static leakage, on the other hand, is
typically caused by the imperfect mechanical sealing of the
prosthetic valve when its flaps are closed. Because static leakage
also causes the heart muscle to work harder, it must be taken into
consideration in the design and manufacture of a mechanical
prosthetic heart valve.
[0010] The closing mechanism of natural cardiac valves has not been
taken into account in the design of conventional mechanical valve
prostheses. When the flow rate across the valve becomes zero, the
natural aortic valve is already more than 90% closed. In contrast,
conventional mechanical valve prostheses at that same time remain
almost fully open. From this almost fully open position,
conventional mechanical valve leaflets abruptly close with the
large amount of regurgitation. In an aortic position, this occurs
at the very beginning of the diastole, and in the mitral position,
this occurs even more abruptly at the very beginning of the
systole. In conventional mechanical leaflets, the mean closing
velocity of some portions of the leaflets (at 70 beats per minute)
is on the order of 1.2-1.5 m/sec, whereas the highest closing
velocity in a natural valve is 0.60 m/sec. Rapid angular closing
speeds create cavitation in mechanical prosthetic heart valves.
This high closure speed increases the intensity of the impact of
the leaflets upon closure and thus, generates sufficiently large
acoustical vibrations to cause discomfort in the patient, damage
the blood (embolisms), and generates micro-bubble formations in the
blood which may be detected by a transcranial doppler (HITS--High
Intensity Transcranial Signals).
[0011] Thus, conventional mechanical heart valves suffer from
several disadvantages. First, conventional mechanical heart valves
fail to provide optimal blood flow characteristics. Next,
conventional mechanical heart valves allow blood to stagnate behind
the valve leaflets, thus creating the possibility of blood clotting
in those locations. Also, conventional mechanical heart valves may
not provide optimum opening and closing times (e.g., times which
properly emulate a natural human valve). It has not been possible,
in the past, to reproduce the flow characteristics of a natural
valve when using a mechanical prosthesis. Thus, with the use of
conventional mechanical heart valves, embolic incidents and
subsequent mortality may be directly or indirectly linked to the
valve prosthesis.
[0012] Accordingly, there is a need for an improved mechanical
heart valve for implantation into a patient which provides improved
flow characteristics, minimizes blood clotting behind the leaflets,
and provides more natural opening and closing behavior.
SUMMARY OF THE INVENTION
[0013] Accordingly, the present invention is directed to an
improved mechanical heart valve for surgical implantation into a
patient which substantially eliminates one or more of the problems
or disadvantages found in the prior art.
[0014] An object of the present invention is to provide for an
improved mechanical heart valve for surgical implantation into a
patient which provides improved flow characteristics.
[0015] Another object of the present invention is to provide for an
improved mechanical heart valve for surgical implantation into a
patient which minimizes the potential for blood clotting behind the
leaflets.
[0016] Another object of the present invention is to provide for an
improved mechanical heart valve for implantation into a patient
which provides improved (e.g., more natural) opening and closing
behavior.
[0017] Another object of the present invention is to provide for an
improved mechanical heart valve for implantation into a patient
which provides reduced regurgitation and closure volume to thereby
reduce the workload on the heart.
[0018] Additional features and advantages of the invention will be
set forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
[0019] To achieve these and other advantages and in accordance with
the purpose of the invention, as embodied and broadly described, an
exemplary embodiment relates to a rotatable leaflet for a
prosthetic heart valve which includes a main portion having leading
and trailing edge surfaces, and inner and outer surfaces connecting
the leading and trailing edge surfaces, wherein the inner surface
generally defines a convex curvature from the leading edge surface
to the trailing edge surface and the outer surface generally
defines a convex curvature proximate the leading edge surface and a
concave curvature proximate the trailing edge surface, and first
and second winglet portions situated on opposite ends of the
leaflet to facilitate pivoting or rotation of the leaflet as it
opens and closes.
[0020] Another exemplary embodiment relates to a rotatable leaflet
for an early-closing prosthetic heart valve including a main
portion having leading and trailing edge surfaces, and inner and
outer surfaces connecting the leading and trailing edge surfaces,
wherein the inner surface generally defmes a convex curvature from
the leading edge surface to the trailing edge surface and the outer
surface generally defines a convex curvature proximate the leading
edge surface and a concave curvature proximate the trailing edge
surface. First and second winglet portions are situated on opposite
ends of the leaflet to facilitate rotation of the leaflet, and
closure means is included for causing the leaflet to rotate toward
a closed position prior to substantial back flow of blood through
the heart valve.
[0021] Yet a further exemplary embodiment relates to mechanical
prosthetic heart valve, the valve including an annular housing
having an inner circumferential surface and at least one leaflet
disposed adjacent to the inner circumferential surface and capable
of rotation between an open position in which blood can flow
through the heart valve and a closed position in which blood is
prevented from flowing through the heart valve. The leaflet
includes a main portion having leading and trailing edge surfaces
and inner and outer surfaces connecting the leading and trailing
edge surfaces, wherein the inner surface generally defines a convex
curvature from the leading edge surface to the trailing edge
surface and the outer surface generally defines a convex curvature
proximate the leading edge surface and a concave curvature
proximate the trailing edge surface. First and second winglet
portions are situated on opposite ends of the leaflet to facilitate
rotation of the leaflet.
[0022] Another exemplary embodiment relates to a mechanical
early-closing prosthetic heart valve, the valve including an
annular housing having an inner circumferential surface and at
least one leaflet disposed adjacent to the inner circumferential
surface and capable of rotation between an open position in which
blood can flow through the heart valve and a closed position in
which blood is prevented from flowing through the heart valve. The
leaflet has closure means for causing the leaflet to rotate toward
a closed position prior to substantial back flow of blood through
the heart valve.
[0023] A further exemplary embodiment relates to a mechanical
prosthetic heart valve including an annular housing having an inner
circumferential surface and at least one leaflet disposed adjacent
to the inner circumferential surface and capable of rotation
between an open position in which blood can flow through the heart
valve and a closed position in which blood is prevented from
flowing through the heart valve. The leaflet includes a main
portion having leading and trailing edge surfaces and inner and
outer surfaces connecting the leading and trailing edge surfaces,
and first and second winglet portions situated on opposite ends of
the leaflet to facilitate rotation of the leaflet, and first and
second leaflet pivot structures adapted to cooperate with the first
and second winglets, respectively, to facilitate rotation of the at
least one leaflet between the open and closed positions. Each of
the first and second leaflet pivot structures includes an inflow
projection extending from the inner circumferential surface of the
housing and adapted to contact one of the winglet portions in the
open and closed positions, and a closing projection extending from
the inner circumferential surface of the housing and adapted to
contact one of the winglet portions in the closed position, wherein
the closing projection and the inflow projection are configured and
spaced from one another to increase flow velocity proximate the one
of the winglet portions.
[0024] Still another exemplary embodiment relates to a mechanical
prosthetic heart valve including an annular housing having an inner
circumferential surface and defining at least one opening through
the annular housing, and at least one leaflet disposed adjacent to
the inner circumferential surface and capable of rotation between
an open position in which blood can flow through the heart valve
and a closed position in which blood is prevented from flowing
through the heart valve. The leaflet includes a main portion and
first and second winglet portions situated on opposite ends of the
leaflet to facilitate rotation of the leaflet, wherein no portion
of the at least one leaflet is received within the at least one
opening during rotation between the open and the closed position to
provide for increased blood flow proximate to one of the winglet
portions.
[0025] Still a further exemplary embodiment relates to a mechanical
early-closing prosthetic heart valve, the valve including an
annular housing having an inner circumferential surface, and at
least one leaflet disposed adjacent to the inner circumferential
surface and capable of rotation between an open position in which
blood can flow through the heart valve and a closed position in
which blood is prevented from flowing through the heart valve. The
leaflet includes an earlyclosure means for creating a tendency for
the leaflet to rotate toward the closed position such that the
leaflet is substantially closed prior to the initiation of back
flow of blood through the heart valve.
[0026] A final exemplary embodiment relates to a mechanical
early-closing prosthetic heart valve, the valve including an
annular housing having an inner circumferential surface, and at
least one leaflet disposed adjacent to the inner circumferential
surface and capable of rotation between an open position in which
blood can flow through the heart valve and a closed position in
which blood is prevented from flowing through the heart valve. The
leaflet includes surfaces with complex curvatures for creating a
tendency for the leaflet to rotate toward the closed position such
that the leaflet is substantially closed prior to the initiation of
back flow of blood through the heart valve.
[0027] It is to be understood that both the general description
above, and the following detailed description are exemplary and
explanatory and are intended to provide further explanation of the
invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The accompanying drawings which are included to provide a
further understanding of the invention and constitute a part of
this specification, illustrate embodiments of the invention and
together with the written description, serve to explain the
principles of the invention. In the drawings:
[0029] FIG. 1 is an elevated isometric view of a preferred
embodiment of a multi-leaflet mechanical heart valve according to
the present invention with the leaflets in the fully open
position;
[0030] FIG. 2 is another elevated isometric view of a preferred
embodiment of a multi-leaflet mechanical heart valve according to
the present invention with the leaflets in an open position;
[0031] FIG. 3 is the elevated isometric view of FIG. 2 in
accordance with the present invention with the leaflets in the
fully closed position;
[0032] FIG. 4 is the elevated isometric view of FIG. 2 in
accordance with the present invention with the leaflets in a
partially open position;
[0033] FIG. 5 is a top plan view of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets in the fully open position;
[0034] FIG. 6 is a top plan view of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets in the fully closed position;
[0035] FIG. 7 is a bottom plan view of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets in the fully closed position;
[0036] FIG. 8 is a bottom plan view of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets in the fully open position;
[0037] FIG. 9 is a bottom plan view of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets removed;
[0038] FIG. 10 is a top plan view of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets removed;
[0039] FIG. 11 is an isometric view of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets removed;
[0040] FIG. 12 is a partial cross-sectional isometric view taken
along line 12'-12' in FIG. 11 of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets removed;
[0041] FIG. 13 is a cross-sectional plan view of the housing of a
preferred embodiment of a multi-leaflet mechanical heart valve
according to the present invention;
[0042] FIG. 14 is a side view of a preferred embodiment of a
leaflet for a multi-leaflet mechanical heart valve according to the
present invention;
[0043] FIG. 15 is an isometric view of a preferred embodiment of a
leaflet for a multi-leaflet mechanical heart valve according to the
present invention;
[0044] FIG. 16 is a front view of a preferred embodiment of a
leaflet for a multi-leaflet mechanical heart valve according to the
present invention;
[0045] FIG. 17 is a top view of a preferred embodiment of a leaflet
for a multi-leaflet mechanical heart valve according to the present
invention;
[0046] FIG. 18 is a bottom view of a preferred embodiment of a
leaflet for a multi-leaflet mechanical heart valve according to the
present invention;
[0047] FIG. 19 is a top plan view of a preferred embodiment of a
leaflet for a multi-leaflet mechanical heart valve according to the
present invention with three differing cross sectional views
included;
[0048] FIG. 20 is a cross-sectional view taken along line 20'-20'
in FIG. 17 of the profile of a preferred embodiment of a leaflet
for a multi-leaflet mechanical heart valve according to the present
invention;
[0049] FIG. 21 is a cross-sectional view taken along line 21'-21'
in FIG. 5 of a preferred embodiment of a multi-leaflet mechanical
heart valve according to the present invention with the leaflets in
the fully open position;
[0050] FIG. 22 is a cross-sectional view taken along line 22'-22'
in FIG. 6 of a preferred embodiment of a multi-leaflet mechanical
heart valve according to the present invention with only one of the
leaflets which shown in the fully closed position;
[0051] FIG. 23 is an enlarged cross-sectional view taken along line
21'-21' in FIG. 5 of a preferred embodiment of a multi-leaflet
mechanical heart valve according to the present invention with the
leaflets removed;
[0052] FIG. 24 is a graphical representation of the performance of
a preferred embodiment of a multi-leaflet mechanical heart valve
according to the present invention in the aortic position at three
differing heart rates;
[0053] FIG. 25 is a graphical representation of the performance of
a preferred embodiment of a multi-leaflet mechanical heart valve
according to the present invention in the mitral position at three
differing heart rates; and
[0054] FIG. 26 is a a cross-sectional view similar to FIG. 21 which
illustrates a preferred embodiment of a sewing ring for a
multi-leaflet mechanical heart valve according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0055] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings. For example, FIG. 1 shows
an elevated isometric view of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets in the fully open position so that
blood can flow through the heart valve.
[0056] As illustrated in FIG. 1, the multi-leaflet mechanical heart
valve 100 generally includes an annular housing 105 and rotatable
leaflets 110 (as used herein, the term annular is taken to
encompass any continuous surface). The housing 105 includes inner
and outer circumferential surfaces, as detailed below (as used
herein, the phrase circumferential surface is taken to mean the
boundary surface of any closed shape). The housing 105 has three
concave portions 115 and three convex portions 120 around its top
surface, as well as six openings therein (called windows herein)
125 and six inflow projections 130. Note that the inflow
projections 130 extend from the inner circumferential surface of
the housing 105 into the blood flow path F.
[0057] Housing 105 may be constructed of any rigid biocompatible
material. For example, housing 105 may be constructed from any
biocompatible metallic material, such as chromium, nickel-tungsten,
and titanium. Housing 105 may also be constructed of any rigid
biocompatible organic material such as, for example, pyrolytic
carbon. Furthermore, housing 105 may be constructed from any
biocompatible polymeric material, such as a biocompatible plastic
material. In the preferred embodiment, housing 105 is machined from
a solid metallic rod.
[0058] Like housing 105, the leaflets 110 may be constructed of any
rigid biocompatible material (metallic, organic, or polymeric). In
the preferred embodiment, leaflets 110 are preferably fabricated
from pyrolytic carbon. The leaflets 110 of the preferred embodiment
have two complex curved, non-parallel surfaces.
[0059] FIG. 2 shows an elevated isometric view of a preferred
embodiment of a multi-leaflet mechanical heart valve according to
the present invention with the leaflets 110 rotated to an open
position. FIG. 2 also more clearly illustrates the structure on
housing 105 which facilitates rotation of and retains leaflets 110.
Each leaflet 110 has two winglets 205 (angled portions at the ends
of each of the leaflets) with a main portion disposed therebetween.
Winglets 205 rest on inflow projections 130 (at least when the
leaflets are in the closed position). In addition to the six inflow
projections 130, housing 105 also has three closing projections
200, six winglet guide paths 210, and six winglet guide arcs 215.
The leaflet pivot structure of the heart valve of the preferred
embodiment which retains the leaflets 110 and its winglets 205
within the housing 105 may be informatively compared to the
structure described in U.S. Pat. No. 5,123,918 which is
incorporated by reference herein. As shown in FIG. 2, windows 125
communicate with the blood flow through the heart valve 100 at
regions denoted as 220. Thus, windows 125 allow blood to flow
across the back of the winglets 205 and substantially wash the
leaflet pivot region in both the open and closed positions. This
washing helps to greatly reduce blood stagnation behind the
winglets 205, and thus reduces the likelihood of formation of a
local blood clot or thrombus in this region.
[0060] Note that the windows 125 may be made any shape and size
which allows for appropriate structural rigidity in the housing 105
and optimum washing flow through the windows and into the leaflet
pivot region. In the preferred embodiment, windows 125 are
triangular in shape.
[0061] Although housing 105 may be made in any annular shape, the
housing of the preferred embodiment has three concave portions 115
and three convex portions 120 around the top surface of its
circumference, i.e., a scalloped arrangement. These concave
portions 115 and convex portions 120 play a special role during the
surgical implantation of valve prothesis 100. During implantation,
a sewing ring (see FIG. 26, for example) is attached to the outer
circumference of housing 105. The surgeon then stitches through the
tissue and through the sewing ring to attach the valve in its
desired location. If the surgeon inadvertently places one or more
of the stitches around the housing 105, when the stitches are
pulled tight, the geometry of housing 105 will move the misplaced
stitches towards concave portions 115 rather than convex portions
120. Thus, there is little opportunity for a suture to be looped
over the convex portions 120 of the housing 105 and thereby impede
the opening and closing of the leaflets 110.
[0062] FIG. 3 an elevated isometric view of a preferred embodiment
of a multi-leaflet mechanical heart valve according to the present
invention with the leaflets in the fully closed position to prevent
blood flow through the heart valve. As shown, housing 105 also
includes six leaflet capture projections 300 which help to prevent
the leaflets 110 from being easily removed from their pivot/hinge
structures. The effective closing angle of the complex curved
leaflet may be defined by the chord of the leaflet in its middle
section. Note that in the preferred embodiment, the chord of
leaflets 110 preferably close to an angle of about 30.degree. to
about 40.degree. with respect to the inflow plane of the housing
105.
[0063] With the leaflets 110 in the closed position, the angle or
pyramid shape of the closed leaflets 110 also channels the flow
through the windows 125 of the valve housing 105 which results in
improved washing by blood flow across the back of the winglets 205
and completely washes the leaflet pivot region. Again, this washing
helps to greatly reduce blood stagnation behind the winglets 205,
and thus reduces the likelihood of formation of a local blood clot
or thrombus in this region.
[0064] FIG. 4 shows an elevated isometric view of a preferred
embodiment of a multi-leaflet mechanical heart valve according to
the present invention with the leaflets rotated into a partially
open position (50% open--half way between the fully open position
and the fully closed position). In this position as well as any
position in which the leaflets 110 are at least partially open,
blood flows across the back surface of the leaflets 110 and through
the windows 125 to completely wash the leaflet pivot region. As
mentioned above, this washing helps to greatly reduce blood
stagnation behind the winglets 205, and thus reduces the likelihood
of formation of a local blood clot or thrombus in this region.
[0065] FIG. 5 is a top plan view and FIG. 8 is a bottom plan view
of a preferred embodiment of a multi-leaflet mechanical heart valve
according to the present invention with the leaflets in the fully
open position. As shown, the open leaflets 110 divide the blood
flow through the valve 100 into several distinct flow paths. Main
flow path 500 extends along the central axis of valve 100, while
outer flow paths 505 are delineated by the open leaflets 110. Note,
as shown in FIGS. 1 and 2, winglets 205 of leaflets 110 do not
completely cover windows 125 when leaflets 110 are in the open
position. Thus, in this position, as well as any open position,
blood flows through windows 125 to completely wash the leaflet
pivot region, reducing the possibility of stagnation or blood
coagulation in this region.
[0066] Although the opening angle of the leaflets 110 may be
optimized for differing requirements, the chord of the leaflets 110
of the preferred embodiment open to an effective angle of about
75.degree. to about 90.degree. with respect to the inflow plane of
the housing 105. The effective opening angle of the complex curved
leaflet may be defined by the chord of the leaflet in its middle
section. This opening angle, coupled with the unique contour of the
leaflets, provides for a central flow valve, similar to the natural
valves of the heart. This results in a reduced pressure gradient or
pressure drop across the valve in the open position when compared
with most conventional mechanical heart valves.
[0067] FIG. 6 is a top plan view and FIG. 7 is a bottom plan view
of a preferred embodiment of a multi-leaflet mechanical heart valve
according to the present invention with the leaflets in the fully
closed position. As shown, in the preferred embodiment, the
leaflets 110 close the main and outer flow paths 500 and 505
respectively. However, in some instances, it may be desirable to
leave a small gap between the leaflets in the closed position. It
has been discovered that a small gap, while allowing for minor
static leakage, tends to improve some performance characteristics,
e.g., reduces the harmful effects of cavitation (by increasing the
cavitation threshold) at the trailing surfaces of the leaflets
during closing. This small gap need not be continuous or constant
along the intersection of the leaflets 110. It may be a gap which
is widest at the pointed tips of the leaflets 110 and get
progressively narrower radially towards the housing 105. It is
noted that a very small opening between the leaflets only near
their tips is shown in the figures (due to manufacturing).
[0068] FIG. 9 is a bottom plan view and FIG. 10 is a top plan view
of a preferred embodiment of a multi-leaflet mechanical heart valve
according to the present invention with the leaflets 110 removed.
This figure illustrates the structure on housing 105 which
facilitates rotation of and retains leaflets 110. As shown, this
structure includes six inflow projections 130, three closing
projections 200, six winglet guide paths 210, six leaflet capture
projections 300, and six winglet guide arcs 215.
[0069] FIG. 11 is an isometric view of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets removed. As shown, each window 125 is
placed just above a winglet guide path 210, the winglet guide path
210 being defined between an inflow projection 130 and a closing
projection 200. Also shown in this figure is the sewing ring
receiving portion 1100 of housing 105. Although in the preferred
embodiment sewing ring receiving portion 1100 is an extended part
of housing 105, other sewing ring attachment arrangements could be
considered.
[0070] FIG. 12 is a partial cross-sectional isometric view taken
along line 12'-12' in FIG. 11 of a preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention with the leaflets removed. As illustrated, inflow
projection 130 includes a non-uniform surface portion 1205. I has
been discovered through testing that additional wear resistance may
be achieved through the use of this non-uniform, asymmetrical
surface on one side of the inflow projection 130 as it mates with a
complementary seating surface on each leaflet 110 (provides for
surface interface contact rather than point interface contact).
[0071] FIG. 13 is a cross-sectional plan view of the housing 105 of
a preferred embodiment of a multi-leaflet mechanical heart valve
according to the present invention. Although differing
cross-sections could be considered, in the preferred embodiment, a
converging nozzle crosssection is utilized. As shown, housing 105
of the preferred embodiment includes converging section 1200 as
well as sewing ring receiving portion 1100. Thus, housing 105 of
the preferred embodiment converges in the flow direction F which
minimizes flow separation and turbulence on the inflow side of the
valve during forward flow through the open valve. The converging
nozzle also reduces the pressure drop or pressure gradient across
the valve during forward flow through the open valve when compared
to other heart valves which have a rather abrupt or blunt shape on
the inflow side of the housing. Thus, the housing of the preferred
embodiment has improved flow characteristics and minimizes pressure
or energy losses and flow separation through the open valve.
[0072] FIG. 14 is a side view of a preferred embodiment of a
leaflet 110 for a multi-leaflet mechanical heart valve according to
the present invention. The preferred embodiment of the leaflet 110
according to the present invention includes a winglet 205 at each
side of the main portion of the leaflet 110. FIG. 15 is an
isometric view of a preferred embodiment of a leaflet 110 for a
multi-leaflet mechanical heart valve according to the present
invention. The main portion comprises inner flow surface 1400,
outer flow surface 1405, leading edge surface 1410, and trailing
edge surface 1415. As mentioned above, leaflet 110 includes two
winglet seating portions 1500 which mate with inflow projections
130. As depicted in this figure, outer flow surface 1405 of leaflet
110 is concave along a line extending between the winglets 205.
[0073] Although the preferred embodiment of a leaflet 110 for a
multi-leaflet mechanical heart valve according to the present
invention is somewhat triangular in shape (because three leaflets
are utilized), other shapes and numbers of leaflets may be utilized
without departing from the scope or spirit of the present
invention.
[0074] FIG. 16 is a front view, FIG. 17 is a top view, and FIG. 18
is a bottom view of a preferred embodiment of a leaflet 110 for a
multi-leaflet mechanical heart valve according to the present
invention. As shown in these figures, winglets 205 include winglet
outer surface 1600 and winglet inner surface 1605. Winglet outer
surface 1600 is the surface that is washed by the blood flow
through windows 125. As depicted in FIG. 18, inner flow surface
1400 of leaflet 110 is convex along a line extending between
winglets 205.
[0075] FIG. 19 is a top plan view of a preferred embodiment of a
leaflet 110 for a multi-leaflet mechanical heart valve according to
the present invention with three differing cross sectional views
included. The section cuts (A, B, and C) show the changing cross
section of the preferred embodiment of a leaflet 110 for a
multi-leaflet mechanical heart valve according to the present
invention from centerline A-A to just short of winglet 205. As can
be seen, section A-A shows a cut of varying thicknesses and
contours, and section C-C near the winglet 205 shows a cut with a
lesser variation in thickness and less pronounced contours. Section
B-B shows an intermediate cut exemplifying the transition between
A-A and C-C. Preferably, the leaflet is symmetric about section
A-A.
[0076] FIG. 20 is a cross-sectional view taken along line 20'-20'
in FIG. 17 of the profile of a preferred embodiment of a leaflet
110 for a multi-leaflet mechanical heart valve according to the
present invention. As shown, inner flow surface 1400 has a convex
curvature from leading edge surface 1410 to trailing edge surface
1415. Outer flow surface 1405 has an S-shaped curvature from
leading edge surface 1410 to trailing edge surface 1415. Outer flow
surface 1405 has a convex curvature 2005 proximate the leading edge
surface 1410. Furthennore, outer flow surface 1405 has a concave
curvature 2010 proximate the trailing edge surface 1415.
[0077] The shape of the preferred embodiment of the leaflets 110
minimizes flow separation in the open position and enhances early
closure of the leaflets. As will be appreciated by one skilled in
the art of fluid mechanics, the shape of the leaflet 110 affects
the pressure distribution over its surface as the blood flows over
the around it. As shown in FIG. 20, leaflet 110 according to the
present invention has an approximate virtual pivot axis at a
location shown at 2000. Thus, during operation the pressure
distribution over the leaflet will affect the rotational tendency
of leaflet about the virtual pivot axis 2000.
[0078] Given the shape of the inner and outer flow surfaces, the
differences between the static surface pressure along the inner
flow surface P.sub.I and the outer flow surface P.sub.O and in view
of the location of virtual pivot axis at a location shown
approximately at 2000, the leaflet 110 is caused to tend towards
rotation to a closed position. These pressure differentials are
created by the airfoil-like shape of the leaflet 110 in the flow
direction F. The fluid mechanics (including pressure gradients
thereof during flow) of an airfoil are well known to those skilled
in the fluid mechanics art. The early closure of the mechanical
heart valve according to a preferred embodiment of the present
invention starts as flow F through the valve 100 decelerates and
the pressure field reverses. In the aortic position the leaflets
110 are substantially closed before the flow reverses, similar to
the function of a natural aortic valve.
[0079] In another aspect, the inner and outer flow surfaces, 1400
and 1405, respectively, are advantageously designed such that in
fully opened position of the leaflets the surface tangents of both
flow surfaces at the trailing edge surface 1415 and the outer flow
surface 1405 at the leading edge surface 1410 are substantially
aligned in the direction of flow F to limit flow separation and
eddy formation (turbulence) as blood flow leaves the trailing edge
surface 1415 of the open leaflets 110. In accordance with a
preferred embodiment of the present invention, the surface tangent
of the inner flow surface 1400 proximate the leading edge surface
1410 of the leaflet 110 forms an angle of preferably about
0.degree. to about 30.degree. with respect to the flow direction.
Thus, flow separation on both the inner and outer surfaces, 1400
and 1405, respectively, of the leaflet 110 is minimized.
Accordingly the leaflets 110 of the mechanical heart valve 100
according to the present invention reduce turbulence, flow
separation, and energy losses associated with flow through the open
valve.
[0080] FIG. 21 is a cross-sectional view taken along line 21'-21'
in FIG. 5 of a preferred embodiment of a multi-leaflet mechanical
heart valve according to the present invention with the leaflets
110 in the fully open position. FIG. 21 clearly illustrates the
interaction of winglets 205 with the winglet guide paths 210 and
winglet guide arcs 215. Also, this figure shows that the distance
between inflow projections 130 and the closing projection 200
decreases in the blood flow direction. Thus, winglet guide paths
210 create a nozzle effect to direct blood flow through windows 125
to substantially wash the rear surface of winglets 205 to minimize
stagnation.
[0081] FIG. 22 is a cross-sectional view taken along line 22'-22'
in FIG. 6 of a preferred embodiment of a multi-leaflet mechanical
heart valve according to the present invention with only one of the
leaflets 110 shown in the fully closed position. As shown, when in
the closed position, leaflet 110 rests upon inflow projections 130
and the closing projection 200. As also illustrated in this figure,
leaflet capture projections 300 help to retain leaflet 110 in
housing 105.
[0082] FIG. 23 is an enlarged cross-sectional view taken along line
21'-21' in FIG. 5 of a preferred embodiment of a multi-leaflet
mechanical heart valve according to the present invention with the
leaflets 110 removed. Like FIG. 21, this figure shows that the
distance between inflow projections 130 and the closing projection
200 decreases in the blood flow direction due to the widening shape
of the projections 130, 200. Thus, winglet guide paths 210 act as
nozzles to direct blood flow through windows 125. This nozzle
creates increased flow velocity into and around the windows 125 and
winglet guide arcs 215. This figure also shows the aerodynamic and
smoothed sculpting of inflow projections 130 and the closing
projection 200 in the blood flow direction. These aerodynamic
profiles help to limit flow separation and eddy formation
(turbulence) as blood flows across these elements.
[0083] FIGS. 24 and 25 are graphical representations of the
performance of a preferred embodiment of a multi-leaflet mechanical
heart valve according to the present invention in the aortic and
mitral positions respectively at three differing heart rates (50,
70, and 120 beats per minute). As shown in FIG. 24 in the aortic
position, the preferred embodiment of a multileaflet mechanical
heart valve according to the present invention begin to close very
early. In fact, as illustrated, closure begins just after the flow
peak (as flow decelerates and the pressure field reverses) and the
valve the leaflets are substantially closed before the flow
reverses (at V=0), similar to the function of a natural aortic
valve. This early closure time is made possible by the flow
characteristics of the preferred valve housing 105 as well as the
preferred leaflets 110 which tend towards closure because of their
novel geometry.
[0084] This closing behavior differs dramatically from that of
conventional mechanical valve prostheses. As mentioned above, in
conventional mechanical valve prostheses at the time when the flow
rate becomes zero through the valve, conventional mechanical valve
prostheses remain 90% open. Thus, with conventional mechanical
valve prostheses, a significant portion of the closure (more than
90%) occurs during regurgitation (backward flow) of blood through
the valve, and thus the closure is very rapid and entails a large
amount of dynamic leakage (regurgitation). Thus, this very rapid
closing under high pressure backward flow can lead to numerous
undesirable results (cavitation, HITS, and unnecessary stress on
the heart muscle). In contrast, the preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention begins to close just after the flow peak (as flow
decelerates and the pressure field reverses) and the valve's
leaflets are substantially closed (approximately 90%) before the
flow reverses (at V=0). Thus, the preferred embodiment of a
multi-leaflet mechanical heart valve according to the present
invention begins to close early and begins to close very slowly.
Because the leaflets are almost completely closed prior to the
initiation of the high pressure backward flow, the preferred
embodiment of a multi-leaflet mechanical heart valve according to
the present invention reduces the likelihood of cavitation, HITS,
blood trauma, and regurgitation.
[0085] Of course, it should be understood that the closure
performance of the present invention could be adjusted to meet
desired criteria, such as a desired closing percentage at zero flow
velocity (initiation of backwards flow), or timing of the
initiation of closure rotation with respect to the maximum flow
velocity. Preferable adjustments to the design could comprise
modification of the airfoil-like geometry of the leaflets 110 to
affect the pressure distributions along the inner and outer flow
surfaces 1400 and 1405, respectively, a structural modification to
the pivot structure to relocate the virtual pivot point of the
leaflet, a reshaping of the leaflet to alter its center of mass or
its neutral point, etc. The present invention conceives that
optimal valve closure performance occurs between 50% to >90%
closed before the flow reverses.
[0086] Finally, FIG. 26 is a a cross-sectional view similar to FIG.
21 which illustrates a preferred embodiment of a sewing ring for a
multi-leaflet mechanical heart valve (in the aortic position)
according to the present invention. As shown, this preferred sewing
ring is attached to the outer circumference of housing 105 at
sewing ring receiving portion 1100.
[0087] As illustrated in the detailed description, the improved
mechanical heart valve for implantation into a patient in
accordance with the present invention substantially eliminates one
or more of the problems or disadvantages found in the prior art.
The novel structure, as particularly pointed out in the written
description and the appended drawings hereof, provides a improved
mechanical heart valve for implantation into a patient which
provides improved flow characteristics, minimizes blood clotting
behind the leaflets, and provides more natural opening and closing
behavior.
[0088] It will be apparent to those skilled in the art that various
modifications and variations can be made in the mechanical heart
valve for implantation into a patient of the present invention
without departing from the spirit or scope of the invention. Thus,
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the disclosure hereof and any equivalents of the
structures disclosed herein.
* * * * *