Experimental Studies On Hemodynamics Of Arteriovenous Flaps And The Modification Of Clinical Application

Arteriovenous flaps have been developed for more than ten years, however the cause of frequent occurrence of necrosis and hemodynamics of the flap to be obscure. A new model by using lateral thoracic arteriovenous flap in rabbits was designed by our Department, i.e. the lateral thoracic vein was arterialized by means of anastomosis with brachial artery, the dorsal thoracic vein was reserved as a efferent vessel. After the venous flap was arterialized, we observed the changes of microcirculation with microangioscopy which revealed that most of blood refluxed directly into efferent vein through venule shunt. The arterial blood flowed into capillary from venule being the principal form of circulation, other forms such as circle circulation, reperfusion, and passive perfusion were merely complementary. Physiological circulation developed (arteriole→capillary→ venule) in late arterialized stage,and was far inferior to countercurrent circulation. The capillary patency was only 10-20% in the early arterialized stage, it increased to 80-90% while three days later. The hypertensive and hyperoximic arterial blood damaged the venous endothelial cells after the vein was arterialized, and resulted in cell swelling, fissuring, exfoliating and thrombosis, consequently the effective microcirculation volum became decreased. we also observed ischemia of the superficial layer of the flap by LDF (Laser Doppler Flowmeter), blood distribution was mainly affected by venous valve in ECT examining. According to the fact that the venous endothelial cells required time to adapt arterial blood and the expansion could increase capillaries in number. The vein of flap was arterialized in situ. at the same time, a skin expander was implanted beneath the pre-transplanted arteriovenous flap. Ten weeks later. the flap was transplanted, the survival rate of arteriovenous flap increased remarkably. i.e. from 39.13% to 86.36%, and contracture rate from 32.08% to 8.9%, both of them are statistically significant(P<0.01). Clinically we operanted upon three cases with forearm arteriovenous flaps, two of them were for nose reconstruction, the remaining one for contraction of hand from injury, all these flaps survived. Satisfactory result were obtained in one year follow-up.