Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Flexible leaflet
Patent
1998-11-17
2000-07-11
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Flexible leaflet
623 218, A61F 224
Patent
active
060866128
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a prosthetic mitral heart valve comprised of a support housing (stent) with a base ring carrying two posts extending substantially in the axial direction of the ring via arcuate walls which serve to affix two flexible cusps [leaflets] and whose free ends form an inward abutment for the cusps [leaflets].
Such mitral heart valves are sutured by means of a suture ring fastened on the base ring in the body tissue.
The first mitral heart valves known from the state of the art had a circular tubular valve housing in which the two cusps [leaflets] were arranged and which had configurations corresponding to shapes cut from a cylindrical surface and which in the closed state braced against one another and in the open state lay against the cylinder wall of the valve housing. As has already been indicated in DE 27 42 681 B2, the closing characteristics of such heart valves were not optimal. Furthermore, a relatively long valve housing was required. To provide assistance as to this point, it was proposed in the aforementioned publication, instead of two cusps [leaflets] to utilize only a single membrane which corresponded to a part of the surface of an elliptical cylinder and which was cut from a circular cylinder. The valve housing was then an elliptical cylinder formed form a circular tube cut at an angle of 90.degree., whereby the membrane was affixed along half the periphery of this cut edge between its two extremal points which corresponded to the posts mentioned at the outset. In this embodiment which eliminated the need for two cusps [leaflets], a folding of cusps [leaflets] in their closed condition as they lay against one another was eliminated but one could not prevent an unsatisfactory valve closure.
In prosthetic heart valves the varying physiological loading conditions arose in the form of different closing pressure differentials to which the heart valve must be matched which thereby posed a further problem. With such closing pressure differentials, radial force components are applied by the cusps [leaflets] to the posts mentioned at the outset and which deform radially inwardly toward the center of the valve. With increasing closing pressure differentials, the cusps [leaflets] can cave in and thus bulge inwardly so that they lie against one another with practically complete overlapping of the cusps [leaflets] and thus a desirable sealing of the valve, although with higher pressure differentials, the overlapping can be excessive at the free cusp [leaflet] edges and that can give rise to undesired folding of the cusps [leaflets]. To reduce the high stresses in the upper cusp [leaflet] regions which correspond to the boundaries at the stent peaks and the natural commissures, it has already been proposed to construct the posts so that they will be flexible in their upper portions. This can, however, lead to undesirable creeping effects and hence premature material fatigue. In order to limit deformation of the posts radially inwardly toward the valve axis, it has thus been proposed in DE 42 22 610 A1 to make the free post ends rigid, especially by an accumulation of material in the form of a prismatic inner layer in the free post ends which in cross section is triangular. The prismatic inner layer should taper in a concave manner toward the stent base, i.e. toward the inlet region of the heart valve.
It is the object of the present invention to improve the mitral heart valve described at the outset by imparting to it a new shape and a new structural configuration so that a potential countervailing functional detriment to the heart and the valve will be avoided. This object is achieved with the prosthetic mitral heart valve according to claim 1 which is characterized in accordance with the invention in that the base ring--considered in plan view--has a closed nonround shape with a common longitudinal axis, but two half transverse axes of unequal size, whereby the posts lie along the longitudinal axis and form the transition regions from one to the other half shape and whereby the wall
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Adiam Medizintechnik GmbH & Co. KG
Dubno Herbert
Jackson Suzette J.
Willse David H.
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