The relative importance of reduced arterial inflow versus reduced venous outflow in determining flap necrosis remains undefined, even though this is critically important in understanding the effects of pharmacologic agents on flap survival. By means of a rat bipedicled ventral island flap, the amount of random flap necrosis was examined in four experimental groups: (1) unilateral arteriovenous ligation (n = 19), (2) unilateral vein ligation (n = 20), (3) unilateral artery ligation (n = 20), and (4) alternate side vein and artery ligation (n = 18). No necrosis occurred on the side of the vein ligation in groups 2 and 4, indicating the independently reducing venous outflow does not cause flap necrosis. A predictable necrosis occurred ipsilateral to artery ligation in groups 1 (37.63 ± 17.34 percent), 3 (32.74 ± 17.32 percent), and 4 (15.70 ± 9.86 percent). These data indicate that the rat ventral island flap is more sensitive to a decrease in arterial inflow than to a decrease in venous outflow. This model may therefore be useful in clarifying the effect and determining the mechanism of action of pharmacologic agents that after flap survival.
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