Venous valves can improve the severe symptoms of patients with post thrombotic syndrome suffering from swelling and ulcerations of their legs. This condition can be caused by stenosis and occlusions of the veins and deterioration of the venous valves. Certain techniques have been developed to surgically restore incompetent valves or to implant devices that aid in such restoration. However, there remain many situations in which a valve is compromised to the extent that these options are not effective and valve replacement must be considered. By replacement of the venous valves, the capillary venous pressure can be decreased in this group of patients eventually improving their condition.
Venous valves have been proposed that consist of a stent device combined with a moving valve being mounted to the stent. However, stents can reduce the effective orifice area of the valve which increases the transvalvular pressure gradient. A further drawback to this valve is that a stent has fixed dimensions and remains in contact with the total circumference of the inner venous surface which, therefore, can irritate a large amount of the venous wall, especially the endothelium. This can be followed by intimal hyperplasia and thrombosis. Further, trauma to the wall of the vein is induced by shear stress between the wall components and the stent, because the venous diameter changes normally. The failure to accommodate growth of the patient is particularly problematic for children undergoing valve replacement, for example. A continuing need exists, therefore, for improvements in valve replacement systems and in methods for placement of such valves.
USPTO Backgrounds
USPTO Backgrounds