Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Having rigid or semirigid pivoting occluder
Patent
1998-01-12
2000-02-01
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Having rigid or semirigid pivoting occluder
A61F 224
Patent
active
060197919
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a buttress for cardiac valve reconstruction of atrioventricular cardiac valves.
The mitral and tricuspid valves are located in the left and right atrioventricular openings, respectively, of the heart and serve to prevent regurgitation of blood from the ventricle into the atrium when the ventricle contracts during systole.
The mitral valve, which is surrounded by a dense fibrous ring known as the annulus, comprises two valve cusps or leaflets of unequal size, the large or anterior leaflet adjacent the aortic opening and the smaller posterior leaflet. The line at which the leaflets come together is called the commissure.
The tricuspid valve comprises three leaflets, usually referred to as the anterior, posterior and septal cusps, which are attached to a fibrous ring known as the annulus.
The mitral valve is subjected to significantly higher back pressure than the tricuspid valve. Accordingly, it is more common to require surgery to repair a mitral valve than a tricuspid valve and, therefore, the discussion herein is primarily concerned with mitral valve reconstruction. However, it will be understood that the same principles apply in respect of both mitral and tricuspid valve reconstruction.
The most common defect leading to mitral valve dysfunction is a dilation of the posterior two-thirds of the annulus which corresponds to the posterior leaflet. Thus, in repairing a mitral valve, it is sometimes necessary to reduce the annulus in its physiological dimensions by repairing the dilated posterior two-thirds thereof. Similar concepts apply to the correction of tricuspid valve defects.
In a normal heart, the mitral and tricuspid annuli move in a dynamic and non-planar way with each cardiac cycle. The circumference of the mitral and tricuspid annuli reduce during systole, so that their respective surface areas reduce by about 20-250%, and then enlarge correspondingly during diastole. The movement of each annulus, which is non-planar, is difficult to describe but would be similar to a pitching, yawing, rolling or rotation motion. All the components of each annulus do not necessarily move to the same degree.
One solution for severe atrioventricular valve dysfunction is total valve replacement. However, it is generally agreed that cardiac valve reconstruction by annuloplasty is preferable to valve replacement.
One such known annuloplasty buttress comprises a rigid annular or part-annular member which is dimensioned to fit against the base of the valve leaflets and is secured in place by sutures. Known rigid annular (or closed) annuloplasty rings affect the movement of the annulus by preventing normal movement, specifically, by restricting it to planar movement. This reduces ventricular function and, if the ventricle is compromised already, is likely to reduce its efficiency further. Another disadvantage of such non-planar movement is a tendancy to force the rigid ring to dehisce or be torn loose from the annulus by the securing sutures being pulled through the tissue. This happens as a result of the stress caused by restraining the annulus from undergoing normal physiological changes during each cardiac cycle. Furthermore, the closed nature of a rigid ring prevents the natural change in the circumference of the annulus, in particular, that which occurs during diastole (the relaxation phase of the cardiac cycle) when the surface area of the mitral and tricuspid valve orifices increase by 20-25%. In addition, the rigid closed ring, in particular, limits the movement of the anterior mitral leaflet in the inter-trigonal region. This effectively limits the ability of the closed ring system and, at high flow rates across the mitral or tricuspid valve, is likely to produce obstruction/stenosis.
Known rigid part-annular (or open) rings suffer less from the problems of rigid closed rings. However, their inherent rigidity restricts normal movement of the annulus and, thereby, depresses ventricular function. Furthermore, because of the restricted non-planar movement of the annulus during each c
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