Enhancement of fibrinolysis with ultrasound energy.

The effect of ultrasound energy on fibrinolysis of artificial thrombus in vitro was investigated. Thrombi produced by the Chandler loop method were exposed to low-energy ultrasound (5,000-6,000 Pa) in an ultrasound bath (48 kHz) for 60 seconds. Fibrinolysis with urokinase was enhanced from 40.6% +/- 1.8% to 59.2% +/- 2.6% (mean +/- standard deviation) with ultrasound exposure after a 60-minute incubation. Ultrasound alone without urokinase resulted in no fibrinolysis. In a second experiment, a newly developed miniature ultrasound-emitting ceramic element (2 x 1 x 5 mm) was attached to the tip of a catheter. Ultrasound exposure (225 kHz) from this device markedly enhanced fibrinolysis with urokinase from 8.9% +/- 1.5% to 37.3% +/- 0.8% (total ultrasound exposure 60 seconds, intensity 30 mW/cm2) after a 30-minute incubation. After a 120-minute incubation, fibrinolysis with ultrasound exposure was 61.1% +/- 1.8% versus 46.7% +/- 0.5% for the unexposed group. Ultrasound enhancement of fibrinolysis was less pronounced with longer incubation time (60 or 120 minutes). Ultrasound energy enhanced fibrinolysis with urokinase, especially in the early phase of lysis. This new device may shorten the time needed to complete fibrinolysis and reduce total drug dosage needed for treatment of thromboembolic diseases.