Two-leaflet heart valve

A heart valve prosthesis has an annular valve body with a central circular passageway and a pair of valve leaflets supported for pivotal movement between closed and open positions. Guides formed with spheroidal surfaces project in opposite directions along the pivotal axis of each leaflet and are received in spheroidal depressions in a pair of upstanding, diametrically opposite supports. The supports are formed with stops outside of the depressions which contact the distal surface of the leaflets at a region apart from the spheroidal guides and determine the open position.

BACKGROUND OF THE INVENTION 
This invention is related to heart valve prostheses for replacement of 
defective natural valves and more particularly to heart valve prostheses 
using pivoting valve members. 
Various types of heart valve prostheses have been developed which operate 
hemodynamically as a result of the pumping action of the heart. Some of 
these valves which have been used employ a ball-and-cage arrangement, 
whereas others have used a disc-type arrangement for the valve member. 
Exemplary of a disc of the free floating type is U.S. Pat. No. 3,534,411, 
issued Oct. 20, 1970. Various disc-type valves having a pivotal 
arrangement have been developed, such as that shown in U.S. Pat. No. 
3,546,711 to Bokros, issued Dec. 15, 1970, and that shown in U.S. Pat. No. 
3,859,668, issued Jan. 14, 1975. 
Disc-type heart valves have also been developed which use two members or 
leaflets, instead of a single disc, which leaflets rotate about parallel 
axes as a part of the opening and closing of the valve. It is the latter 
type of heart valve prostheses to which the present invention is directed. 
SUMMARY OF THE INVENTION 
The invention provides an improved version of a heart valve prosthesis 
which uses a pair of pivotal leaflets that have their pivotal axes defined 
by a pair of generally spherical edge surfaces extending in opposite 
directions. These spherical guides or ears are received in mating 
depressions formed in a pair of supports which extend upward from the 
annular valve body. Adjacent straight edges of the leaflets engage each 
other in the closed position, and stops which determine the open position 
of the leaflets are provided on the upstanding supports in a region 
outside of the depressions. As a result, the most important wear areas, 
namely the bearing surfaces which determine the rotational movement that 
occurs between the spherical ears and the mating depressions, can be 
designed solely to withstand the rotational movement and need not be 
concerned with providing the stops.

IN THE DRAWINGS 
FIG. 1 is a perspective view of a heart valve embodying various features of 
the invention and having a pair of leaflet members which are shown in the 
open position; 
FIG. 2 is a section view taken generally along the line 2--2 of FIG. 1; 
FIG. 3 is a section view similar to FIG. 2, but showing the leaflets in the 
closed position; 
FIG. 4 is a section view taken generally along the line 4--4 of FIG. 1; 
FIG. 5 is a plan view of a leaflet from the heart valve of FIG. 1; 
FIG. 6 is an enlarged sectional view taken along line 6--6 of FIG. 5 
showing the bearing surface in phantom outline; 
FIG. 7 is a fragmentary plan view of the valve body depicted in FIG. 3; 
FIG. 8 is an enlarged fragmentary view illustrating the upstanding supports 
with the leaflets in a mid-way location between their open and closed 
positions; 
FIG. 9 is a section view taken along line 9--9 of FIG. 8; 
FIG. 10 is a vertical section view of a modified version of a valve body, 
which is very similar to that illustrated in FIGS. 1 through 4, shown with 
only one leaflet installed and depicted in the open position; 
FIG. 11 is a fragmentary plan view of the valve body shown in FIG. 10; and 
FIG. 12 is an enlarged, fragmentary, section view generally similar to FIG. 
3 showing the modified heart valve of FIGS. 10 and 11 in the closed 
position. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Illustrated in FIG. 1 is a heart valve 11 which has an annular valve body 
or housing 13 which carries a pair of pivoting leaflets or valve members 
15 which open and close to control the flow of blood through a central 
passageway 17 in direction of the arrow 19 (FIG. 2). The leaflets 15 are 
supported about eccentric axes by a pair of diametrically opposed supports 
21 which extend upwardly from the annular valve body 13 as depicted in 
FIG. 1. It should of course be understood that the valve 11 can operate in 
any orientation and is not significantly affected by gravity; however, for 
ease of explanation, the valve 11 is shown and described with the supports 
21 upstanding from the annular valve body 13. 
The valve body 13 is formed with a peripheral groove 23 about its exterior 
surface that accommodates a suturing ring (not shown) which may be any of 
the various type already well known in the art. The suturing ring, of 
course, facilitates the sewing or suturing of the heart valve 11 to the 
heart tissue. 
The passageway 17 through the valve body 13 is preferably circular, and 
accordingly the internal wall surface 25 of the valve body which defines 
the passageway 17 preferably has the shape of a right circular cylinder. 
As best seen in FIG. 7, this cylindrical interior shape is carried out 
totally through the valve so that the facing surfaces of the supports 21 
are also generally cylindrical and do not extend into the flow path of 
blood through the valve. 
The valve body 13 and the leaflets 15 may be made of any suitable material 
that is biocompatible and nonthrombogenic and that will take the wear to 
which it will be subjected during countless openings and closings of the 
leaflets. Preferably, the components are made from isotropic graphite, 
such as that sold under the tradename POCO, which has been suitably coated 
with pyrolytic carbon, such as that sold under the trademark PYROLITE, 
which gives excellent compatibility and wear-resistance. 
The leaflets 15 are generally flat and may have a uniform thickness 
throughout, as best seen in FIG. 2. The pivotal axis for each of the 
leaflets is of course eccentric to the leaflet and is defined by the 
location of a pair of oppositely extending ears or guides 27 which are 
machined or ground so that the outer edge 28 of each is that of the 
surface of a spheroid and preferably that of the surface of a perfect 
sphere. One edge 29 of the leaflet 15 is straight, and the major edge 31 
is curved in a manner to match the inner surface of the passageway 17. 
Accordingly, the outline of the arcuate edge 31 is generally defined by a 
plane cutting the right cylindrical interior wall surface 25 of the valve 
body. 
As best seen in FIG. 3, the flat surface of the leaflet, in the closed 
position, is at an angle A to the axis of the passageway 17. This angle 
should preferably be between about 60.degree. and about 70.degree.. The 
edge surface portion 33 of this arcutate portion of the leaflet 15 is 
machined so as to be a section of the surface of a right circular cylinder 
having a diameter just slightly less than the diameter of the passageway 
17 so as to provide a close fit along the arcuate boundary when the 
leaflets 15 are in the closed position illustrated in FIG. 3. The 
straight-line portion 29 of the leaflet boundary has a planar edge surface 
35 which is disposed at angle A to the flat upper or distal surface of the 
leaflet (FIG. 3). 
As best seen in FIGS. 4 and 7, the length of the straight edge portion 29 
of the boundary is slightly longer than the diameter of the pasageway 17, 
and there is a short transitional edge portion 37 (FIG. 5) which is 
perpendicular to the straight edge boundary 29 and extends for a short 
distance therefrom until it intersects the spherical surface portion 28 of 
the ears 27. The surface of the transitional edge portion 37 is 
perpendicular to the upper and lower surfaces of the leaflet. The corners 
at intersections of the edge 29 and the edges 37 are rounded slightly to 
prevent chipping. 
The upstanding supports 21 contain a pair of spherical depressions 41 of a 
diameter slightly larger than the diameter of the spherical surface 
portions 28 of the ears. The material from which the valve body 13 is made 
has sufficient resiliency to allow the leaflets 15 to be snapped into 
position with the ears being received in the depressions 41. In addition, 
a central portion 43 of the upstanding supports 21 is machined to provide 
a flat vertical surface which provides clearance for the pivoting movement 
of the transitional edges 37 of the leaflets. Accordingly, the distance 
between the diametrically opposite vertical surfaces 43 is just slightly 
greater than the length of the straight edge boundary 29 of the leaflets. 
The machining or milling to form the vertical surfaces 43 provides a 
vertical groove 45 within which the transitional edges of the leaflets 15 
are free to move. As best seen in FIGS. 8 and 9, the side surfaces 47 of 
these vertical grooves are used to determine the open position of the 
leaflets 15. Preferably, the leaflets 15 are allowed to pivot through 
about 55.degree. to about 65.degree. of angular movement, and the side 
surfaces 47 of the groove are cut at angle B (FIG. 3) to the vertical 
plane, which angle is the difference between angle A and the amount of 
movement desired. Preferably, angle B, which determines the orientation of 
the leaflets in the open position, is between about 5.degree. and 
10.degree.. The side surfaces 47 of the groove are planar and 
perpendicular to the vertical surface 43 of the groove. 
One example of a heart valve 11 designed for aortic location may have an 
outer diameter of about 24 mm. and a central passageway 17 about 21 mm. in 
diameter. The length of the straight edge portion 29 of the leaflets may 
be about 23 mm. The radius of the spherical surface portions 28 of the 
ears may be about 2.4 mm., and the radius of curvature of the depressions 
41 is nearly equal to that of the ears--within about 6%. In the open 
position, as depicted in FIG. 2, the main portions of the leaflets 15 
swing downward until the transitional edge regions 37 of the distal 
surface contact the stops which are provided by the side surfaces 47 of 
the groove. During the opening movement, blood flows through the valve 11 
in the direction of the arrow 19. This flow of course occurs on the 
pumping stroke of the heart as the respective ventricle contracts. 
At the end of the stroke, the respective ventrical relaxes to draw more 
blood into the chamber from the atrium, and the back pressure within the 
left aorta causes the leaflets to swing or pivot to the closed location 
depicted in FIG. 3. The proportioning of the leaflets 15 is such that they 
pivot about the axis which is defined by the radii of the spherical 
surface sections of the ears 27 until the cylindrical edge surface 33 of 
the arcuate portion of each leaflet contacts the interior side wall 25 of 
the passageway, thus sealing the outer region of the passageway. As 
indicated above, the radius of curvature of the ears may be either 
slightly longer, equal to or slightly smaller than that of the depressions 
41. Moreover, some slight amount of additional clearance can be provided 
by reducing the longitudinal distance between the ears 27. If, as is 
preferred, the radius of curvature of the depressions is slightly larger, 
the ears will move slightly within the depressions 41 until the 
straight-edge surface portions 35 of the two leaves contact each other, 
closing the central portion of the passageway to blood flow. 
The heart valve is felt to contain certain improvements which provide not 
only good flow characteristics and ease of machinability, but also long 
lifetime. As best seen in FIG. 7, the central passageway 17 through the 
valve 11 has the shape of a right circular cylinder with no protrusions 
thereinto. Accordingly, this surface can be formed by a single boring or 
milling operation. The arrangement also provides for smooth flow of blood 
along the cylindrical interior surface of the wall 25. 
The main wear occurs at the region where the spherical ear surfaces 28 
pivot in relative movement within the spherical depressions 41 and this 
can be controlled by the proportioning of the radii of curvature and/or 
the clearance. By making the radius of the ears slightly larger, the wear 
region will be located near the widest part or base of the ears, as best 
seen in FIG. 5. Because these spherical surfaces need only define the axis 
of swinging or pivoting movement and because the regions of engagement in 
order to stop the leaflets in their precise open and closed position are 
separated therefrom and defined exterior of the depressions superior 
results are obtained relative to an arrangement where the ears 27 
themselves were relied upon to determine the open and/or closed position 
of the leaflets. 
As earlier indicated, it is the engagement of the transitional boundary 
portions with the side surfaces 47 of the groove that stop the leaflets in 
the desired open position, and the engagement of the arcuate edge surfaces 
33 of the leaflets that define the closed position. By proportioning the 
radii of curvature within the limits of about 6% and/or adjusting the 
clearance, the wear can be spread over a fairly large total surface area 
without unduly increasing the effect of friction, and both excellent 
sealing of the blood passageway and wear resistance are found to result. 
Although the invention has been described with regard to a particular 
preferred embodiment which constitutes the best mode presently known to 
the inventor, it should be understood that various changes and 
modifications as would be obvious to one having the ordinary skill in this 
art may be made without departing from the scope of the invention which is 
defined solely by the appended claims. 
In this respect, should it be desired to achieve an even greater seal in 
the closed position along the arcuate boundary of the leaflets and to 
relieve somewhat the holding of narrow tolerances to achieve precise 
interengagement of the abutting straight edge surfaces, a ledge 51 as 
depicted in FIGS. 10-12, can be provided. The ledge 51 is created by 
machining a valve body 13' so that a central passageway 17' is provided 
with a slightly smaller diameter above the region wherein the arcuate 
boundary portion 31' of the leaflets 15' will reside. As best seen in 
FIGS. 10 and 11, the ledge 51 preferably terminates at the region of the 
depressions 41', and when such full length ledge 51 is used, the upper 
surface of the arcuate region of the leaflet 15' will both stop and seal 
tightly against the undersurface of the ledge, as depicted in FIG. 12. 
However, such a ledge 51 could be terminated sooner if it were primarily 
used as a stop instead of as a seal, by blending the ledge into the 
cylindrical wall, and the ledge 51 would function as an effective stop 
even if it only extended for a distance of about 10-15 degrees of the 
arcuate edge 31 of the leaflet. The relative dimensions of the radii of 
curvature remain the same as before mentioned. 
Various of the features of the invention are set forth in the claims which 
follow.