Automatic Valve For Prothesis

Automatic Valve For Prothesis-52
Many have failed in early experimental evaluation, with some advancing to the clinical arena, but few remain in research and development.

The standard dictionary definition of “artificial” is “not arising from natural growth.” Therefore, and for this review, an artificial venous valve is not considered as a “de novo” venous valve. Implantation of cryopreserved allograft pulmonary monocusp patch to treat nonthrombotic femoral vein incompetence.

In general, two categories of artificial venous valves have been studied: valves devoid of autogenous components; and valves constructed, at least partially, from autogenous components.

As a preamble to the clinical trial, dog erythrocyte antigen–matched and cryopreserved veins containing valve allografts were transplanted into recipient dogs with experimental hind limb venous insufficiency.

Following ligation of a post-implant highflow d AVF at 3 to 6 weeks, all four transplants remained patent and competent for three more weeks, at which time sacrifice demonstrated acceptable histologic findings.14 The inner surface had an endothelial-like cell covering, and cusp sinuses were free of thrombus.

All 10 canine implants thrombosed in 8 days.8 Animal studies, or occasionally even unrelated clinical studies, raised hope.

Automatic Valve For Prothesis Bibliography Research Paper Mla

Platinum or pyrite-carbon–covered, titanium, center-hinged bileaflet valves implanted in the dog femoral vein had 100% patency and competency at three months.9 Unfortunately, extensive neointimal overgrowth resulted in valve failure within 2 years.10 These results hold some promise that modifications might be able to extend valve life into a useful clinical range. Experimental repair of venous valvular insufficiency using a cryopreserved venous valve allograft aided by a distal arteriovenous fistula. Decellularization of allograft veins containing valves could provide a transplant devoid of potentially immunogenic donor cells. A cryopreserved decellularized allograft, used as an arteriovenous fistula (AVF) for dialysis access, incited little antigenic response, with good overall function.11 When implanted into the right ventricular outflow tract, a relatively high flow situation, pulmonary valve allografts functioned well for at least 6 months in a sheep model.12 Implantation of pulmonary valve allografts as an adjunct to the Ross procedure did not induce an antibody response, as determined by panel reactive antibody (PRA) testing.12 However, decellularized vein–containing valve allografts, implanted as venous valves in recipient sheep, and unaided by supportive anticoagulation, all failed in six weeks.13 Although this animal study was unsuccessful, clinical experience, with the same material as an AVF or cardiac valve, suggests that further study might be rewarding. Teebken OE, Puschman C, Aper T, Haverich A, Mertsching H. In such cases, there is an opportunity for an artificial venous valve to be used as a native valve. Hemodynamic evaluation of a bioprosthetic venous prosthesis. For decades, substitute valves have been studied experimentally, raising hope of bench-to-bedside transfer. A variety of techniques have been used clinically, and improved venous hemodynamics and valve competency have been demonstrated. Glutaraldehyde-preserved venous valve transplantation in the dog. However, the majority of these valve studies await confirmation by other investigators over extended periods. NONAUTOGENOUS VALVES Some investigations have never advanced past the point of a promising valve studied for hemodynamic responsiveness. In a lyophilized cadaveric vein, a valve acts mechanically much like a native valve when rehydrated.6 The cusps withstood greater than 350 mm Hg retrograde pressure without leakage, and the closure time was 0.31 0.03 seconds. Venous reflux repair with cryopreserved vein valves. It is apparent from the current literature that venous ulceration will recur even after the most aggressive treatment of superficial and perforator disease in patients with clinical class C5,6 disease.1 Ulcer recurrence is more common in patients with postthrombotic deep venous insufficiency (~ 70%), but is also seen in patients with primary deep venous insufficiency (~ 30%). The role of proximal iliac vein obstruction may be more prominent than once expected,2 but surgery to correct deep venous insufficiency (DVI) remains an appropriate option in selected patients. Human saphenous vein allograft bypass grafts: immune response.

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