Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Having rigid or semirigid pivoting occluder
Patent
1991-07-10
1993-08-17
Green, Randall L.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Having rigid or semirigid pivoting occluder
A61F 224
Patent
active
052364488
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with heart valve prostheses.
Various types of synthetic heart prosthesis are known which operate haemodynamically when used in the surgical replacement of a heart valve, such as the mitral or aortic valve.
One known type of heart valve prosthesis is the St. Jude valve, which comprises a valve body having a passageway for the flow of blood therethrough from upstream to downstream, and a pair of flat leaflets which are pivotally supported in the passageway and movable between a closed position inhibiting blood flow and an open position permitting blood flow therethrough.
Another known type of heart valve prosthesis is the Duramedics valve which is a bileaflet valve in which the leaflets are curved in a plane parallel to the pivot axis of the leaflets.
Such heart valve prostheses have peripheral pivot points, the pivot axes being substantially parallel to the junction between the two leaflets, and each axis defining a chord on the respective leaflet. Such heart valve prostheses all have points of weakness at the pivot points, which can cause catastrophic failure and/or promote blood coagulation. Moreover, the leaflets provide obstructions to the flow of blood through the valve and substantially disturb the laminarity of such blood flow.
It has been previously proposed, in broad terms, that vitreous carbon would be a suitable material for the production of heart valve prosthesis. Vitreous carbon artefacts are produced by careful, controlled pyrolysis of resin mouldings is described in "Polymeric Carbons, Carbon Fibre, Glass and Char" by G. Jenkins and K. Kawamura, Cambridge University Press, 1976. In this method, the resin material (such as a phenolic resin or furan resin) is cast and cured as a block, machined to the form of the final artefact, and then slowly pyrolysed over a prolonged period.
We have now devised an improved bileaflet heart valve prostheses, which enables the properties of vitreous carbon, both during the pyrolysis process, and in the resulting artefact, to be optimised.
According to the present invention, therefore, there is provided a heart valve prosthesis comprising a unitary annular valve body having a passageway for the flow of blood therethrough from upstream to downstream, and a pair of leaflets pivotally mounted in said valve body for pivotal movement between a closed position, in which closed position said leaflets lie contiguous with one another so as to obturate said passageway to the flow of blood therethrough, and a fully open position, in which the inner edges of said leaflets are substantially parallel to one another in a downstream position, so as to permit blood flow through said passageway, each of said leaflets being pivotally mounted adjacent the outer edge thereof about a pivot axis which is substantially parallel to said inner edges and which does not intersect the respective leaflet, in which each of said leaflets and said valve body is a precision moulded, homogeneous monolithic vitreous carbon artefact having an as-moulded surface of optical quality.
The valve body and the leaflets have, in the as-moulded state, all the surface characteristics of the mould surfaces; further machining or polishing is generally unnecessary and, indeed, undesirable. The mould surfaces employed to produce the vitreous carbon artefacts are therefore of optical quality. By optical quality, we mean herein a surface finish with a centre-line average (Ra) of less than 0.05 micrometers.
The annular valve body and the leaflets are all homogeneous (that is, they are essentially free of granular or powdered filler, fibrous reinforcement, or other inclusions). They are further monolithic, being devoid of any coating, and have a purity of substantially 100% (that is, less than about 50 ppm of impurities). The valve body and the leaflets are generally impermeable to helium and heavier gases.
The bileaflet heart valve prosthesis according to the invention is generally such that the passageway formed when the leaflets are in the fully open position is substantially
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J. C. Bokros, "Carbon Biomedical Devices", 1977, Carbon, vol. 15, pp. 355-371.
Angelini Gianni
Pistolesi Claudio
Cardio Carbon Company Ltd.
Green Randall L.
Willse D.
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