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BACKGROUND: External ultrasound has a synergistic effect on thrombus disruption with thrombolytic agents in vitro. We hypothesized that transcutaneous ultrasound could augment thrombolysis in vivo. METHOD AND RESULTS: Thrombus formation was induced electrically in 48 pairs of iliofemoral arteries of 24 rabbits; arterial occlusions were documented angiographically. In 17 of 24 rabbits, 25000 units/kg streptokinase was then administered intravenously. The pairs of iliofemoral arteries were randomized to receive ultrasound treatment or no ultrasound treatment. Low-frequency (26 kHz) ultrasound (continuous wave, 18 W/cm2) was applied transcutaneously over the area of occlusion. In 7 of 24 rabbits, 14 thrombotically occluded iliofemoral arteries were exposed to ultrasound alone without streptokinase. The results were evaluated through the use of angiography (TIMI grade flow) and histopathology. After 30 +/- 10 minutes of activated sonication combined with intravenous streptokinase, 10 of 17 iliofemoral arteries (59%) treated with transcutaneous ultrasound were widely patent angiographically, with TIMI grade 3 flow. Histologically, the patent arteries had only minimal focal moral thrombus. The angiographic patency rate was significantly lower in the control groups: 1 of 17 arteries (6%) treated with streptokinase alone (P = .0012) and 1 of 14 arteries (7%) treated with ultrasound alone (P = .0036). CONCLUSIONS: In vivo transcutaneous ultrasound significantly augments lysis of thrombi with streptokinase in rabbit iliofemoral arteries.
Luo et al. (Thu,) studied this question.