Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Having rigid or semirigid pivoting occluder
Patent
1997-08-21
1999-10-05
Prebilic, Paul B.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Having rigid or semirigid pivoting occluder
251 65, A61F 224
Patent
active
059615508
DESCRIPTION:
BRIEF SUMMARY
This application is a national stage application under 35 U.S.C. 371 of PCT/FR97/00312 filed Feb. 20, 1997.
The present invention relates to a heart valve activating system and to an activated heart valve.
Artificial heart valves, also known as mitral or aortic prostheses, generally consist of one or two mobile flaps mounted on a seat by means of one or more joints, said seat also being sutured to the patient's natural ducts.
In the working cycle of the valves, the flap opening and closing phases are of very short duration compared with the phases corresponding to blood flow or blocking. Nevertheless, the quality of an artificial heart valve is determined largely by these opening and closing phases, and the precise moment at which they take place in the cardiac cycle.
Generally when an artificial valve is closed and when the pressure difference on either side of the valve orifice inverts, the force which was keeping the flaps closed changes direction and tends to open them. This force, and hence the pressure difference which generates it, have to reach a sufficient level to start the opening of the flap or flaps and simultaneously to initiate blood flow through the prosthesis. The closing of an open mechanical valve which is allowing the blood to flow through takes place when pressure difference on either side of the valve orifice inverts and increases and then ultimately causes a reversal blood flow. This reverse flow then closes the valve by moving its flaps.
In summary, a traditional mechanical valve operates with a delay relative to the pressure fluctuation because a significant pressure difference has to be established before flap movement is initiated. Furthermore, the opening and closing mechanisms of the traditional artificial valves are identical, whether implantation is at the aortic or mitral position, which is not the case for natural valves.
The opening and closing mechanisms of natural valves are such that the natural aortic valve opens at the same time as the ventriculo-aortic pressure difference inverts. This is because a natural aortic valve has no inertia so that it opens under a zero pressure difference, in contrast to delayed operation for a mechanical valve prosthesis. At the end of the systole, the natural valve closes gradually, but rapidly and without reverse flow, under the action of local pressure differences on the lamellae, which are equivalent to the flaps. These local pressure differences precede the overall inversion of the pressure difference between the aorta and the ventricle, said inversion being necessary for initiation of reverse flow. It is for this reason that the natural aortic valve closes without reverse flow at the moment when the aortic pressure becomes greater than the ventricular pressure, whereas it is the reverse flow which closes a mechanical valve prosthesis.
The natural mitral valve actively opens under the effect of the tension of cords attached, on the one hand, to the edges of its lamellae and, on the other hand, to the inner walls of the ventricle. It is the dilation of the ventricle during the diastole which simultaneously causes the drop in ventricular pressure (and hence the inversion of the auriculo-ventricular pressure difference) and the opening of the mitral valve by traction on its cords. Therefore opening of the natural mitral valve is strictly synchronous with the inversion of auriculo-ventricular pressure, whereas a mechanical valve prosthesis opens with a delay because a pressure difference is required in order to open. The closing of the lamellae of the natural mitral valve takes place due to the simultaneous occurrence of several events, particularly, the cords holding the lamellae relax, the lamellae gradually close under the action of local pressure differences (preceding the overall inversion of the pressure difference between the atrium and the ventricle), and the mitral valve orifice contracts (bringing the lamellae closer together). Thus, like the natural aortic valve, the natural mitral valve closes without reverse flow. This is in
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Carpentier Alain
Garitey Vincent
Hassler Michel
Prebilic Paul B.
Societe Industrielle De Combustible Nucleaire-sicn
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