Design And Study On Artificial Extravascular Venous Valve

IntroductionVenous insufficiency is a disease of venous hypertension coused by functional disturbance of valve, with the characteristic of limbs swelling, hyperpigmentation, dermatitis and dermal ulcer. The incidence of venous insufficiency is increasing, approximately 1,200,000 new cases are reported yearly in China. Medical treatment of venous insufficiency syndrome has been associated with a high incidence of failure. Surgical treatment which to aim at valve could promote recirculation of blood and relieve hypertension.But traditional ways of Surgical treatment could not be satisfactory, so scholars had introduced several substitutes of venous valve. Ackroyd introduced venous valve homografs; Rosenbloom introduced that surgically created totally autogenous venous valve with venous endomembrane; Taheri created artificial valve with stainless steel and titanium allegation; some scholars created artificial valve with tissue engineering. These presumptions and designs are still experimental phases, short term effect is satisfactory,but several problems such as thrombopoiesis, endotheliosis, aging of artificial valve should be studied and investigated after it long-term embeddingPart I: Preliminary Study on a new device with valvalfunction: artificial extravascular venous valve[Material and methods] Artificial extravascular venous valve, an equipment which offers regular pressure is placed around the vein, is a novel design for venous insufficiency is proposed. To demonstrate its feasibility by hydrodynamics' study. We designed a block point and a inductive point which are connected by lever with different force arms. Block point, inductive point and lever are fixed in crust. The whole equipment was placed around the vein just like sleevelet. When direct or converse flow occurs, different moments of block point and inductive point control on-or-off of artificial valve. According to the above elements,we develop a prototype of it. The prototype was fixed in a simulating model, filled with solution of sodium chloride, set a pressure difference and liquid flow in it. To against an afterload of 1.96kPa(200mmH₂O), measure two groups of direct flow and antidromic flow, both begin with the pressure difference of 0mmH₂O, add more 20 mmH₂O every time ,measure three tines at each pressure difference, get the average value at each pressure difference.[Results] The direct flow rate reached 0.549L/min when pressure difference was 4.90kPa(500mmH₂O), and the antidromic flow rate only reached 0.028L/min when pressure difference was 4.90kPa(500mmH₂O), the direct flow rate is much more than the antidromic flow rate.Part II: Experimental study of artificial extravascularvenous valve[Material and methods] To design an artificial extravascular venous valve and to validate its function of preventing venous reflux. Dogs were selected as experimental subjects. Using micrurgy to destroy the valves in both sides of common iliac veins, external iliac veins, femoral veins and popliteal veins, establishing theanimal model of refluxing. Embedding artificial valve surrounding one side of external iliac vein of random selecting as experimental group, and the other side as control group. Using ascending phlebography and descending phlebography to check the function of artificial valve. Sacrificing the animals after three days and checking whether the endomembrane develops thrombogenesis or not.[Results] Ascending phlebography and descending phlebography display that blood through the valve smoothly, and it can't reflux, and there have no mural thrombosis by gross appearance.Conclusions1. Artificial extravascular venous valve can block blood stream selectively, less resistance for direct blood stream and great resistance for antidromic blood stream;2. Artificial extravascular venous valve has the function of physiological valve during the short-term after it embed;3. Artificial extravascular venous valve keeps the continuity of venous endomembrane, prevent the thrombopoiesis;4. Several problems such as thrombopoiesis, endotheliosis, aging of artificial valve should be studied and investigated after artificial extravascular venous valve is long-term embed.