Enhancement of Fibrinolysis With 40-kHz Ultrasound

Ultrasound at frequencies of 0.5 to 1 MHz and intensities of > or =0.5 W/cm2 accelerates enzymatic fibrinolysis in vitro and in some animal models, but unacceptable tissue heating can occur, and limited penetration would restrict application to superficial vessels. Tissue heating is less and penetration better at lower frequencies, but little information is available regarding the effect of lower-frequency ultrasound on enzymatic fibrinolysis. We therefore examined the effect of 40-kHz ultrasound on fibrinolysis, tissue penetration, and heating.