U.S. patent number 3,689,942 [Application Number 05/072,449] was granted by the patent office on 1972-09-12 for prosthetic heart valve.
Invention is credited to Richard K. Rapp, 1251 Imperial Dr..
United States Patent |
3,689,942 |
|
September 12, 1972 |
PROSTHETIC HEART VALVE
Abstract
A prosthetic heart valve consisting of a cylindrical housing
having a substantially rectangular opening therein and a plurality
of triangular flaps pivotally secured to the housing within the
opening. The flaps are adapted to pivot open in response to the
flow of blood from the heart and pivot to a sealing position, in
abutment to a sealing ball which controls the position of the
flaps, in response to the back flow of the blood, thereby providing
uni-directional flow.
Inventors: |
Richard K. Rapp, 1251 Imperial
Dr. (Glendale, CA 91207) |
Family
ID: |
26753386 |
Appl.
No.: |
05/072,449 |
Filed: |
September 15, 1970 |
Current U.S.
Class: |
623/2.21;
137/527; 623/2.33; 137/512.1; 137/527.8 |
Current CPC
Class: |
A61F
2/2403 (20130101); A61F 2/246 (20130101); Y10T
137/7903 (20150401); Y10T 137/7839 (20150401); Y10T
137/7898 (20150401) |
Current International
Class: |
A61F
2/24 (20060101); A61f 001/22 () |
Field of
Search: |
;3/1,DIG.3
;137/527,527.4,527.8,512.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
452298 |
|
May 1, 1968 |
|
CH |
|
1500461 |
|
Sep 1, 1967 |
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FR |
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Other References
"A Hinged Prosthetic Cardiac Valve Fabricated of Rigid Components"
by W. .
S. Pierce et al., The Journal of Thoracic & Cardiovascular
Surgery, .
Vol. 56, No. 2, Aug. 1968, pp. 229-235..
|
Primary Examiner: Richard A. Gaudet
Assistant Examiner: Ronald L. Frinks
Attorney, Agent or Firm: Matthew P. Lynch
Parent Case Text
RELATED APPLICATIONS
This application is a continuation-in-part of application Ser. No.
880,674, filed Nov. 28, 1969, entitled "Prosthetic Heart Valve" and
now abandoned.
Claims
What is claimed is:
1. A prosthetic heart valve comprising: an elongated housing having
top and bottom end surfaces and being provided with a rectangular
opening therein intermediate said end surfaces; a sealing means
secured within said housing and located generally axially of said
opening; and a plurality of substantially triangular flaps,
pivotally secured to the inner surface of said housing within said
rectangular opening, said flaps being substantially rigid and sized
to at least substantially seal said opening and adapted to open in
response to the flow of blood from the heart and close in response
to the back flow of blood towards the heart, an apex of said flaps
abutting said sealing means when said flaps are in their closed
position.
2. A prosthetic heart valve in accordance with claim 1, wherein
said housing has an impervious inner surface.
3. A prosthetic heart valve in accordance with claim 2, wherein
said housing has a porous outer surface.
4. A prosthetic heart valve in accordance with claim 1, wherein
said flaps have a depression along one of their apexes, said
depression being complementary to the sealing means for abutment
therewith when said flaps are in their closed position.
5. A prosthetic heart valve in accordance with claim 1, wherein
said sealing means comprises: a ball disposed centrally of the
opening within said housing; and support members secured between
said ball and said housing for rigidly retaining said ball in
position.
6. A prosthetic heart valve in accordance with claim 5, wherein
said ball has a substantially eliptical configuration.
7. A prosthetic heart valve in accordance with claim 1, wherein
said flaps have a compound curvature.
8. A prosthetic heart valve in accordance with claim 7, wherein
said flaps have a sinusoidal configuration.
9. A prosthetic heart valve in accordance with claim 1, wherein
said flaps have a convex upper and lower surface tapering towards
their free apexes.
10. A prosthetic heart valve in accordance with claim 9, wherein
said flaps are tapered towards their free apex and towards the two
sides forming said apex.
11. A prosthetic heart valve in accordance with claim 1, further
comprising: a plurality of support pins, said pins having a
substantially Y-configuration, one end pivotally secured to a
corner of one flap, another end pivotally secured to a corner of an
adjacent flap and the leg fixedly secured to the housing, whereby
said flaps are pivotally secured to said housing by said support
pins.
12. A prosthetic heart valve in accordance with claim 2, wherein
said impervious inner surface slopes inwardly to form the
rectangular opening.
13. A prosthetic heart valve in accordance with claim 1, wherein
said housing is annular and has a substantially C-shaped exterior
configuration.
14. A prosthetic heart valve in accordance with claim 13, further
comprising: a layer of polyethylene terephthalate disposed within
the concave portions of said housing forming said C-shaped exterior
configuration.
15. A prosthetic heart valve in accordance with claim 1, further
comprising: a flap guide disposed upon said flap and adapted to
coact with said sealing means, whereby said flaps are guided into
complementary juxtaposition to each other and in abutment to each
other and in abutment to said sealing means.
16. A uni-directional prosthetic valve comprising: an elongated
housing having top and bottom end surfaces and being provided with
a rectangular opening therein intermediate said end surfaces; a
sealing means secured within said housing adjacent to and centrally
of the rectangular opening; a plurality of triangular flaps
pivotally secured to the inner surface of said housing and within
said rectangular opening, said flaps being substantially rigid and
sized to at least substantially seal said opening and adapted to
open away from said sealing means in response to a flow of fluid in
one direction and to close in abutment to said sealing means
thereby sealing the rectangular opening in response to flow in a
contra direction.
17. A uni-directional prosthetic valve in accordance with claim 16,
wherein said flaps have a depression along an apex, each depression
complementary conforming to the shape of said sealing means,
whereby said sealing means rests partially within said
complementary depression when said flaps are in abutment thereto.
Description
In the human body, blood enters the right auricle from the superior
and inferior vena cavae which drain most of the body. It passes
through the tricuspid valve to the right ventricle and is pumped to
the lungs during systole or contraction of the heart. Blood returns
from the lungs by way of the pulmonary veins to the left auricle
passes into the left ventricle through the mitral valve and during
contraction is pumped out into the aorta, which is a large elastic
vessel whose endothelial lining is continuous with that of the
heart. Located within the heart where the aorta connects to same is
an aortic heart valve which is in essence a on-way valve. When
operating correctly, the aortic heart valve will allow blood to
pass from the left ventricle of the heart through the aortic heart
valve into the aorta and thence throughout the arterial branches
during heart contractions or systole and will prevent the blood
from flowing back into the heart; when the flow or pressure of the
blood is reversed due to the heart ceasing to contract and
proceeding to expand. Since the back pressure of the blood on the
aortic heart valve during the heart's resting cycle reaches a
magnitude of about 200 millimeters of mercury (200 mm Hg) or 3.87
pounds per square inch, it is imperative that the aortic valve be
capable of preventing the back-rushing blood from entering the
heart where it would cause irreparable damage and possibly
death.
In many instances the aortic valves become diseased or damaged in
some way, thereby preventing them from operating in a normal
manner, particularly with regard to preventing the back flow of
blood into the heart. During the last few years great strides have
been made in the area of heart surgery, particularly with regard to
the replacing of malfunctioning heart valves with artificial
prosthetic valves. The most commonly used of these artificial
prosthetic heart valves is the ball and cage type which is inserted
in place of an excised section of the descending aorta. The ball
and cage valve utilizes an elastomer ball which relies, for
extended use, upon the continuing elastomeric properties of the
ball. In addition, such ball valves require a "cage" or retaining
struts to maintain the ball in close proximity to its valve seat
and these retaining struts extend into and across the blood stream,
thus hindering the free flow of blood and causing undesirable
turbulance. Additionally, when such ball valves are open, the flow
of blood must pass around the ball which is a relatively bulky
object and which takes up a significant portion of the
cross-section of the normal blood flow channel. Further, when the
ball valve closes after each systole it does so with an audible
click, causing severe psychological neuroses in the transplant
patient and even more serious is that the ball, in closing, crushes
red blood corpuscles which is a known cause of disease.
In order to solve the aforementioned problems, attempts have been
made to design uni-directional flap valves. Flap valves, however,
while solving some of the problems associated with the ball and
cage valve, have other inherent disadvantages and defects. A
particular problem is in the area of providing areas or pockets
which are not constantly subjected to the washing or flushing
action of the flow of blood therethrough, such pockets provide
prime blood clot forming areas and are highly undesirable and
dangerous to the well being of the patient. Another major problem
with such flap valves is the fact that in all known flap valves a
portion of the flap, when in its open position, extends into the
oncoming flow of blood, causing the blood to flow in a swirling
turbulent pattern which precludes the desirable laminar flow and
additionally causes a fluttering of the valve flaps and a further
eddying of the blood flow, all of which causes severe pressure
differentials about the valve and a resulting insufficiency of
blood flow, particularly in the extremities.
The present invention overcomes the aforementioned problems by
providing a prosthetic heart valve having an annular housing with a
substantially rectangular opening therein. A plurality of
triangular flaps are pivotally secured to the inner walls of the
housing forming the opening, the apexes of the flaps meeting in
complementary sealing relationship in the center of the opening.
The flaps are contoured and pivotally affixed in a manner such as
to be completely responsive to the flow of blood without causing
turbulence or restricting the flow of said blood while allowing a
complete washing or flushing of the valve and only permitting
uni-directional flow. Disposed in the center of the valve is a
sealing ball which is adapted to complementarily receive the apexes
of the flaps to hold them in sealing orientation to prevent the
back flow of blood. The flaps and inner surface of the valve
housing are constructed from an inert, impervious material and the
outer surface of the valve housing is constructed from an inert,
porous material in order to allow the living tissue of the aorta
and heart to grow into the outer surface of the housing while
precluding it from clogging the opening within the housing or
interfering with the functioning of the flaps.
FIG. 1 is a perspective view, partially cut-away, of the prosthetic
heart valve in its open position.
FIG. 2 is a perspective view, partially cut-away, of the prosthetic
heart valve in its closed position.
FIG. 3 is a perspective view of one of the flaps.
FIG. 4 is a view along line 4--4 of FIG. 2.
FIG. 5 is a perspective view, partially cut-away, of an alternate
embodiment of the prosthetic heart valve.
FIG. 6 is a transverse cross-sectional view of FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, wherein like reference numbers
designate like or corresponding parts throughout the several views,
there is shown in FIGS. 1 and 2 a prosthetic heart valve 10.
The valve 10 is adapted to be inserted into the heart as a
replacement for the aortic heart valve or the mitral valve;
therefore, it is preferred that the valve have a housing 11 which
conforms to the shape of its receiving member. However, since both
the heart and the aorta are of an elastic nature, the shape of the
valve housing is not critical. As a preferred embodiment, the
housing 11 has been illustrated as having a substantially
cylindrical exterior configuration. The diameter of the housing 11
will be determined by the diameter of the heart and aorta of its
ultimate recipient; however, since the valve 10 has an expected
unlimited useful life it is within the realm of feasibility that a
larger valve will be utilized in young recipients by stretching the
diameters of the receiving members in order to allow the recipients
organs to grow without requiring that the transplanted valve be
replaced with a larger valve. It will be noted that the housing 11
has a varying outer diameter in that the outer diameter tapers
inwardly as it approaches either end of the cylinder and that the
ends of the cylinder have a radius 12. The tapered and radiused
ends of the housing 11 facilitate the insertion of the valve 10
into the heart and aorta and additionally assist in providing a
relatively obstruction-free smooth vessel for the blood to flow
through.
The housing 11 consists of an outer surface 13 which is of a porous
nature and an inner surface 14 which is impervious. The outer
surface 13 and the inner surface 14 can be bonded together directly
to form an integral structure or they can be bonded together by
means of a metalized layer 15 as illustrated. The utilization of an
outer porous surface 13 allows the living tissue of the heart and
aorta to grow into the housing 11 and permanently retain the valve
10 in its correct position. It is extremely undesirable, however,
for the tissue to extend through the entire housing into the valve
opening itself because then the tissue would tend to interfere with
the operation of the valve and disrupt the flow of blood
therethrough. Therefore, the inner surface should be impervious in
order to preclude this from happening.
The inner surface 14 of the housing 11 is configured to converge to
a radiused lip 16, which forms a substantially rectangular opening
17 at a point intermediate the ends of the housing 11. It will be
noted by referring to the drawings, that a square opening has been
illustrated. This is because, while any rectangular opening will
work, a square opening is preferred. The contour of the inner
surface 14 converging to form the opening 17 is designed to
preclude the blood flowing through the opening 17 from eddying
while still allowing the blood to flow over all parts of the valve
to provide a continuous washing or flushing action in order to
eliminate blood clotting pockets and areas of stagnation. In
addition to the angle and contour of the slope of the inner surface
14, the radiused edge 16 of the rectangular opening 17 assists in
the ensuring of laminar blood flow through the opening 17.
Disposed within the housing 11 substantially centrally of the
opening 17 and adjacent thereto is a sealing means 18. In the
preferred embodiment, as illustrated in FIGS. 1, 2 and 4, the
sealing means 18 comprises a ball 19 of a substantially spherical
configuration which is rigidly held in position by a plurality of
support members 20. While the sealing means 18 has been illustrated
in the preferred embodiment as a sphere, it will be obvious to
someone skilled in the art that the sealing means 18 can assume
other configurations such as an ellipse or a cone, among others.
The support members 20, which hold the ball 19 in position, should
have as small a cross section as possible in order not to hinder
the flow of blood while having sufficient strength and rigidity to
maintain the ball 19 in a constant position within the housing 11.
In the preferred embodiment, the support members 20 comprise small
diameter wires 21 which are embedded in the housing 11 on one end
and secured to the ball 19 on their opposite ends.
Pivotally secured to the inner surface 14 of the housing 11 are
four flaps 22. The flaps 22 are constructed to have a compound
curvature which resembles a sinusoidal curve in order to be
immediately responsive to the flow of the blood from the heart and
to assist in the complete flushing of all the components of the
valve 10 by the flowing blood. The flaps 22 are pivotally connected
to the housing 11 by substantially Y-shaped support pins 23. As
illustrated in FIGS. 1 and 3, one end of the support pin 23 is
pivotally affixed to a corner of a flap 22, another end of the pin
23 is pivotally affixed to a corner of an adjacent flap 22 and the
leg of the pin 23 is fixedly secured within the inner surface 14 of
the housing 11. In other words, the four flaps 22 are pivotally
secured to the housing 11 by four support pins 23, each of the
support pins pivotally connecting one end of two adjacent flaps to
the housing 11. The leg of each pin 23 is disposed within the
housing 11 at each corner of the rectangular opening 17 so that
when the flaps 22, which are of a substantially triangular
configuration, are pivotally supported by the pins 23, one side of
each flap lies in juxtaposition to one of the radiused lips 16
which form the rectangular opening 17. It is an important aspect of
the applicant's invention that the flaps 22 all be of a
complementary configuration and that their manufacturing tolerances
be such that when all four flaps are pivotally connected to the
housing and in juxtaposition to each other that they substantially
close and seal the rectangular opening 17. Research has shown,
however, that due to the viscosity of the blood that a clearance of
approximately 10 microns can be tolerated between the adjacent
flaps in order to allow non-binding action while still providing
complete sealing of the opening 17. In order to provide complete
closing and sealing of the opening 17 when the flaps 22 are in
juxtaposition, the apexes of the flaps are not radiused. FIG. 4
shows the compound curvature of the flaps 22 and their
complementary juxtaposition relationship to the radiused lip
16.
Referring now to FIG. 3, it will be noted that the flap 22 has a
concave depression 24 along its free apex. As illustrated, the
depression represents a segment of a sphere and is specifically
configured to mate in complementary abutment with the underside of
the ball 19 when the flaps 22 are in juxtaposition in their closed
position, as best shown in FIG. 4. Disposed on the upper surface of
the flap 22 along a plane coinciding with the wire 21 is a flap
guide 25. The flap guide 25 comprises a raised surface having a
groove therein, the groove having a concavity sufficient to accept
and partially surround the wire 21.
Referring now to FIGS. 5 and 6, there is shown an alternate
embodiment of the prosthetic heart valve 10 indicated generally by
the numeral 110. The valve 110 comprises a housing 111 which is
annular and has a substantially C-shaped exterior configuration.
The concave exterior surface of the housing 111 is roughened or
knurled to allow the attachment thereto of a polyethylene
terephthalate (Dacron) or Teflon cloth layer 115 to which the
living tissue of the aorta can be secured when the valve is placed
within the body of its user. If a Teflon or Dacron cloth layer is
utilized then it is not necessary to provide that the exterior
surface of the housing 111 be porous since the living tissue of
both the heart and aorta will be securely connected to the inert
cloth layers and it is not necessary that they be able to grow into
the outer surface of the housing. It will be noted by referring to
the drawing that all the edges of the housing 111 are rounded or
radiused in order to facilitate laminar flow of the blood
therethrough. The housing 111 may be constructed from any type of
material which is inert and capable of safe acceptance by the human
body; however, the internal surface 114 should be impervious to
preclude the growth of living tissue therethrough. The inner
surface 114 of the housing 111 is of a modified hour glass
configuration, wherein the upper inner portion 112 has a conical
configuration which progressively decreases in diameter to
terminate in a substantially rectangular opening 117, which is
located intermediate the ends of the housing 111. The opening 117
extends downwardly for a distance less than one-half of its
shortest side and then terminates to form the lower inner surface
113 which has a conical configuration, the diameter of which
increases as it extends away from the opening 117.
Disposed within the housing 111 substantially centrally of the
opening 117 is a sealing means 118. The sealing means 118 comprises
a ball 119 having a substantially eliptical configuration which is
rigidly held in the center of the housing by a plurality of support
members 120, which also have a substantially eliptical
configuration. The support members 120 are secured to both the ball
119 and the inner surface 114 of the housing 111 and have as small
a lateral cross section as possible in order not to impede the flow
of blood while still supporting the ball. In order to preclude the
possibility of turbulent flow about the support members 120 at the
points where they are secured to the ball 119 or the inner surface
114 of the housing 111, the support members 120 are flared at their
attachment points, thereby facilitating laminar flow by such
points.
Pivotally secured to the inner surface 114 of the housing 111 are
four flaps 122. The flaps 122 have a substantially triangular
configuration and are pivotally connected to the housing 111 by
support pins 123 in a manner similar to flaps 22. The flaps 122 are
disposed in complementary relationship to each other and to the
housing walls forming the opening 117 in a manner such that when
they are in the position illustrated in FIGS. 5 and 6 they
completely seal the opening 117 in the same manner as hereinbefore
described. Each of the flaps has a surface contour designed to
provide the least resistance to the flow of blood through the valve
110 when the flaps 122 are in their open position. The most
efficient contour can be determined by tests conducted under a
varying range of parameters including blood viscosity, opening
dimensions, rate of flow, amount of flow, response time required
both for opening and closing and flow pressure. Tests conducted by
applicant have shown that under most conditions the most efficient
flap surface configuration is as illustrated, wherein the upper and
lower surfaces are convex and symmetrical about a center line
through the support pin 123. The cross sectional configuration of
the flaps 122 is effectively an airfoil which tapers to an edge not
only along their free apex but also along the complementary
juxtaposed sides. The flaps 122, in a manner similar to the flaps
22 of FIG. 3, have a concave depression 124 at their free apex. The
configuration of the depression 124 is designed to allow the apex
of the flap 122 to mate with the lower surface of the ball 119 in
complementary sealing abutment when the flaps are in their sealing
position, as shown in FIGS. 5 and 6.
Since the subject valve of applicant's invention is primarily
intended to be used in a human body, all parts of the prosthetic
heart valve must be constructed of materials which are inert,
non-toxic, non-irritating, capable of sterilization and not subject
to corrosion or other attack by body fluids. In addition to the
aforementioned requirements, the materials must be compatable with
each other and possess sufficient rigidity and strength to function
indefinitely without damage. There are all too few materials that
possess all of the required attributes; however, some known
suitable materials are high chromium stainless steel, titanium,
etc., and plastics, such as reinforced inert thermosetting
plastics, including glass reinforced polyesters and epoxys, acrylic
resins, polycarbonate resin, formaldehyde polymers and polyamides;
while all of the above materials will work, the preferred materials
for applicant's device are vitrified carbon or aluminum oxide for
the entire housing and the flaps and "Vitallium", the composition
of which is specifically described in Aeronautical Material
Specification No. 5385c as promulgated by the Society of Automotive
Engineers, for the sealing means and support pins. Vitrified carbon
and aluminum oxide are ideally suited for constructing the housing
11 because they can be made in both a porous manner for the outer
surface 13 and in an impervious manner for the inner surface
14.
In operation during systole, blood is forced from the heart, in the
direction of the arrow, impinging upon the flaps and forcing them
downward about the support pins, as shown in FIG. 1. When the flaps
are in their downward position the entire rectangular opening is
open to allow the flow of blood therethrough and since the sealing
means occupies a minute area, as compared to the opening, the blood
is not restricted thereby in its flow. Due to the curvature of the
flaps they are very responsive to the blood flow and present
negligible resistance; additionally, when the flaps are in their
open position they provide a gap between the wall of the
rectangular opening and the side of the flap in juxtaposition
thereto, thereby allowing blood to flow through the gap and wash
the undersurface of the flap. When the heart comes to rest and
proceeds to expand, the blood starts to back-flow towards the
heart, at which time the blood applies a force against the
underside of the flaps and, due to the curvature of the flaps, they
are forced upwardly into contact with the ball. The configuration
of the flaps is designed so that their reaction time to the
back-flowing blood is almost instantaneous or in the order of
four-tenths of a second for the flaps to move from a fully open
position to a fully closed position. In one embodiment, when the
flaps approach a fully closed position in abutting relationship to
the underside of the ball, the flap guide 25 engages the wire 21,
thereby correcting any misalignment of the flaps relative to the
sealing means 18. When the flaps are all in their upward closed
position the concave depressions at the apexes of the flaps
encircle and abut the lower surface of the ball in a complementary
manner, thereby serving a dual purpose, namely sealing and
alignment. It will be apparent that there is no area of the valve
over which flow does not take place either during normal forward
flow or back flow and this concept is important in assuring that
all interior surface areas are washed to prevent stagnation and
clot formation. After the prosthetic heart valve is inserted into
the recipient's heart there will be a period of time during which
the valve must be artificially secured to the heart and the aorta
in order to give the living tissue sufficient time to grow into the
porous outer surface of the housing when it is utilized. For this
reason, at the time of insertion of the valve which utilizes a
porous outer surface, it is wrapped with a cloth sewing ring made
of polyethylene terephthalate (Dacron) fabric or other synthetic
plastic fabric such as polytetrafluoroethylene and the receiving
member is sutured to the cloth sewing ring to temporarily hold the
valve in place.
For the purposes of exemplification, particular embodiments of the
invention have been shown and described according to the best
present understanding thereof. However, it will be apparent that
changes and modifications in the arrangement and construction of
the parts thereof may be resorted to without departing from the
spirit and scope of the invention.
* * * * *