Correction of incompetent venous valves

Details Correction of incompetent venous valves Correction of incompetent venous valves

1988-03-04

1990-02-27

Apley, Richard J.

Prosthesis (i.e., artificial body members), parts thereof, or ai

Heart valve

Having rigid or semirigid pivoting occluder

606153, A61F 224, A61B 1700

Patent

active

049042548

DESCRIPTION:

BRIEF SUMMARY
FIELD OF INVENTION

This invention relates to the correction of incompetent venous valves.
Venous valves in mammals are usually bicuspid valves, with each cusp forming a sack or reservoir for blood which, under pressure, forces the free edges of the cusps together to prevent retrograde flow of the blood and allow only antegrade flow to the heart. When an incompetent valve attempts to close in response to a pressure gradient across the valve, the cusps do not seal properly and retrograde flow of blood occurs.
There are two chronic venous diseases in which incompetence of venous valves is thought to be an important factor in the pathophysiology. These are varicose veins and chronic deep venous insufficiency.
The varicose vein condition consists of dilatation and tortuosity of the superficial veins of the lower limb and resulting cosmetic impairment, pain and ulceration. Primary varicose veins are the result of primary incompetence of the venous valves separating the superficial venous system from the deep venous system. Secondary varicose veins occur as the result of deep venous hypertension which has damaged the valves of the perforating veins.
Chronic deep venous insufficiency consists of deep hypertension of the lower limb with associated pigmentation, pain, swelling, ulceration and varicose veins.
For the sake of convenience, the invention will be described in relation to the correction of incompetent valves in the venous system of the lower limb in man, but, it is to be understood that the invention is not limited thereto.
The venous system of the lower limb consists essentially of the superficial venous system and the deep venous system. The superficial system includes the great saphenous vein and the small saphenous vein. The deep venous system includes the anterior and posterior tibial veins which unite to form the popliteal vein which in turn becomes the femoral vein when joined by the small saphenous vein.
The initial defect in primary varicose veins often involves localised imcompetence of a venous valve thus allowing reflux of blood from the deep venous system to the superficial venous system. This incompetence is traditionally thought to arise at the saphenofemoral junction but may also start at the perforators. Thus, gross saphenofemoral valvular dysfunction may be present in even mild varicose veins with competent distal veins. Even in the presence of incompetent perforators, occlusion of the saphenofemoral junction usually normalises venous pressure.
The initial defect in secondary varicose veins is often incompetence of a venous valve secondary to hypertension in the deep venous system. Since this increased pressure is manifested at many points, correction of one site of incompetence could clearly be insufficient as other sites of incompetence will be prone to develop. Apart from the initial defect, the pathophysiology is similar to that of varicose veins.
Once the initial incompetence occurs, incompetence in other valves in the system will tend to occur secondary to the venous hypertension.
Apparently, incompetence of venous valves is caused by dilatation of the vein wall. The evidence for this is as follows:
(i) The valves in varicose veins are normal macroscopically and histologically in most cases. The vein wall is more distensible in apparently normal veins in people with varicose veins.
(ii) The valve cusps have a much greater tensile strength than the vein wall.
(iii) Venous function deteriorates during the day as the venous system becomes more dilated.
(iv) Saphenofemoral valves which are incompetent can become competent again at operation when the diameter is decreased by spasm. A similar occurrence has been noted in the superficial femoral vein.
(v) Varicose veins may temporarily appear during pregnancy before the uterus is large enough to cause venous obstruction.
(vi) Forearm veins which are incompetent when full and distended can become competent again when the distal segment is emptied thus reducing the diameter. Valves which are competent can be made incompetent by injection o

REFERENCES:
patent: 2756753 (1956-09-01), Means
patent: 3254651 (1966-06-01), Collito
patent: 3357432 (1967-12-01), Sparks
patent: 3435823 (1969-04-01), Edwards
patent: 3726279 (1973-04-01), Barefoot et al.
patent: 4602911 (1986-07-01), Ahmadi

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