Ultrasound-Assisted Thrombolysis

RATIONALE AND OBJECTIVES.Current use of thrombolytic agents to lyse thrombus, though safe, is complicated by stroke, bleeding, and clot embolization. Therapy may be protracted, resulting in further ischemia and possible tissue loss. Peripheral arterial and graft occlusions often require several hours of thrombolytic therapy, which may occasionally exceed 48 hours and may also require expensive intensive care monitoring. It is desirable to accelerate clot lysis and to thereby reduce the risks and costs associated with the procedure and minimize morbidity. In this article, the authors propose the use of intravascular ultrasound in conjunction with thrombolytic agents to increase the rate of thrombolysis. METHODS AND RESULTS.In-vitro thrombolysis of fresh human blood clots was studied with and without urokinase by using continuous wave, 20-KHz ultrasound at the power levels 1-2 watts. Loss in weight of each clot was used to measure the extent of thrombolysis. Clot lysis was observed when ultrasound and thrombolytic agents were used alone. At modest power levels of 1.0 to 1.5 watts of ultrasonic energy a significant increase in lysis was observed in conjunction with 5,000 units of urokinase. CONCLUSIONS.In the short treatment duration of this invitro study, 5,000 units of urokinase combined with 20-KHz ultrasound energy at 1.0 and 1.5 watts was associated with a greater percentage thrombolysis by weight than either urokinase or ultrasound alone.