Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Flexible leaflet
Patent
1998-10-29
2000-12-26
Milano, Michael J.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Flexible leaflet
623 217, 623910, A61F 224
Patent
active
061652156
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates generally to multi-leaflet one-way valves, and specifically to prosthetic valves for use in the heart and in heart-lung machines and heart-assist devices.
BACKGROUND OF THE INVENTION
Tri-leaflet one-way valves are well-known in the art and are commonly used in heartlung machines, heart-assist devices and as surgical prosthetic implants to replace the heart's natural valves. Such valves must have sufficient strength and resiliency to maintain their shapes and operate securely through a great many cycles, without substantial wear or failure. At the same time, the leaflets must be sufficiently flexible to open and close smoothly, with minimal pressure drop across the valve and without creating undue turbulence or hemolytically damaging the blood cells. Various materials have been used for this purpose, including primarily hemocompatible polyurethane of different grades, as well as silicones, Teflon.TM. and other polymers. Complex, time-consuming processes must generally be employed in order to produce valves having the desired properties. Exemplary prior art patents describing valves of this sort and methods of producing them include U.S. Pat. No. 4,192,020, to Davis, et al.; U.S. Pat. No. 4,222,126, to Boretos, et al.; U.S. Pat. No. 4,629,459, to Ionescu, et al.; and U.S. Pat. No. 4,888,009, to Lederman, et al., which are incorporated herein by reference.
U.K. patent application GB 2,255,394A, by Rottenberg, et al., which is assigned to the assignees of the present invention and is incorporated herein by reference, describes an integral tri-leaflet valve- sleeve structure and a method of producing the structure by injection molding. The structure includes a cylindrical outer sleeve, from which three flexible, fabric-reinforced leaflets extend radially inward, meeting in the center when in the closed position. Fluid pressure exerted on the valve from one end of the cylinder causes the valve to open and allows blood to flow through the cylinder in a desired direction. When the pressure is released, or when pressure is exerted from the opposite end of the cylinder, the valve closes and prevents back-flow of blood in a reverse direction.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide tri-leaflet, one-way valves having leaflets of superior flexibility, so as to open with minimal pressure and close with reduced turbulence and minimal hemolysis.
It is a further object of the present invention to provide a method of producing such valves, and particularly a method of enhancing the flexibility of the valve leaflets.
In one aspect of the present invention, the valves are designed for use in an artificial heart machine, such as a heart-lung machine or heart-assist device.
In preferred embodiments of the present invention, a valve for use in an artificial heart machine comprises a cylindrical sleeve and three flexible leaflets integrally fixed to an inner surface of the sleeve and extending radially inward therefrom. The leaflets open when a fluid pressure is exerted thereon from an inlet end of the cylinder and close when a fluid pressure is exerted from the opposite, outlet end thereof. When there is no pressure differential between the two ends of the cylinder, however, the leaflets maintain a partially open position.
This partially open position is advantageous in that by reducing the closing force of the leaflets, it reduces damage to blood cells that may be caught between the leaflets during closing, but still prevents reverse flow through the valve.
In preferred embodiments of the present invention, the valve comprises elastomeric material, preferably a polyether polyurethane polymer.
In preferred embodiments of the present invention, the leaflets are thin and substantially flexible. Preferably the leaflets have hardness of approximately 70-80 Shore A units. This hardness value is, of course, related to the stiffness of the leaflets. Preferably the leaflets are between 0.1 and 0.3 mm thick.
In some preferred embodiments of t
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patent: 4192020 (1980-03-01), Davis et al.
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patent: 4372743 (1983-02-01), Lane
patent: 4629459 (1986-12-01), Ionescu et al.
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"The Influence of Manufacturing Methods on the Function and Performance of a Synthetic Leaflet Heart Valve" M.E. Leat et al., in Proceedings of the Institution of Mechanical Engineers, vol. 209, Part H: Journal of Engineering in Medicine, (1995) pp. 65-69.
Haimovich Dudu
Rottenberg Dan
Sondak Ehad
H.D.S. Systems Ltd.
Milano Michael J.
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