Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Having rigid or semirigid pivoting occluder
Patent
1996-01-06
1998-09-01
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Having rigid or semirigid pivoting occluder
623900, A61F 224
Patent
active
058005277
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a support housing (stent) for valve and closure members, in particular for heart valve prostheses, having a base ring which carries at least two symmetrically offset posts substantially oriented in the direction of the ring axis and linked together by curved strips for securing at least two flexible webs.
One of the main problems in forming a prosthesis from a stent of this kind is to provide a suitable construction in which the stent posts can be deformed in the implanted state by very small forces or closing pressure differentials in the bloodstream from the form in which they are manufactured or from some other, possibly conical, initial form into a cylindrical state, after which a radially inwardly directed deformation of the stent posts can only take place by the application of large forces.
For better understanding, the closing behaviour and the opening movement of the natural aortic valve will be described. In the natural aortic valve the webs form an integral part of a hose-shaped structure, the aortic root. Adjoining the webs there are hollows in the walls of the aorta, the aortic bulbs. In the case of a prosthesis this is called in the literature an "unstented" valve or conduit valve implant (often without bulbs), in contrast to the stent valves described here. For closure, i.e. in the closed position of the webs, these aortic bulbs serve to provide mechanical strengthening. Without the hollows of the bulbs the aortic valve would not be able to absorb radial components of force in order to counterbalance the forces exerted on it by the webs under diastolic pressure. In artificial stent heart valves these components of force are absorbed by their stent posts, which are thereby deformed radially towards the middle of the valve.
The differences in construction of the stented and unstented valves result in different movement or opening behaviour of the web-like closure elements.
In the unstented valve with bulbs the commissures (in the case of a stent valve the tips of the posts) of the webs are firmly connected to the aortic root. Because of the ability of the aortic root to expand the natural valve can open prematurely. At the start of the systole the ventricular pressure increases through the isovolumetric contraction, so that the commissures move radially outwards. This commissure expansion begins even before the valve opening proper. The movement of the commissures gives rise to a force acting tangentially on the web. Thereby the curvature of the web is decreased, the webs gradually separate from one another, and they are drawn into an open position. The very small amount of valve opening brought about in this way can be recognised without any detectable forward flow and in the absence of any increase in aortic pressure. In the course of the systole the expansion of the aortic root further increases as the aortic pressure increases. In systole the aortic valve thus forms a tube with increasing diameter and, from the point of view of hydrodynamics, a diffuser. Besides this, the ability of the bulb valve to expand serves as it were to regulate the web overlap area in the closed state and thus prevents folding within the web under varying physiological load conditions, i.e. different closing pressure differentials. If one considers the web of the natural valve in the closed position at different pressure differentials, with increasing maximum pressure differential across the valve the aortic pressure, and thereby also the diameter of the aorta at the position of the commissures, increases at the same time. As a result the valve webs lift downstream. Through these actions the area of web overlap decreases. The bulb valve obviously adapts to different load conditions through variation in web overlap areas.
PRIOR ART
From the prior art, e.g. from DE 38 34 545 A1 and DE 38 90 571 T1, stents are known which have a cylindrical base ring which is prolonged by three posts each offset circumferentially by 120.degree. and narrowing in the axial direction. The bays
REFERENCES:
patent: 4441216 (1984-04-01), Ionescu et al.
Jansen Josef
Jansen Ulrich
Adiam Medizintechnik GmbH & Co. KG
Willse David H.
LandOfFree
Support housing for valve and closure members, in particular for does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Support housing for valve and closure members, in particular for, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Support housing for valve and closure members, in particular for will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-265314