[The ultrasound contrast medium levovist increases the thrombolytic effect of low frequency ultrasound]

Therapeutic application of ultrasound is a promising tool to develop an alternative or additional treatment modality of acute vessel occlusion. It has previously been shown that ultrasound enhances the effect of pharmacologic thrombolytic agents and has a thrombolytic potential in "stand-alone" therapy. The purpose of this study was to determine, whether the presence of the echo contrast agent Levovist further increases the thrombolytic efficacy of ultrasound.

Thrombolytic efficacy of low-frequency (20.5 kHz) continuous-wave ultrasound was evaluated. Fresh human blood clots (age 3-6 h) were sonicated for 10 min at an intensity of 0.35 W/cm2. The thrombolytic effect of ultrasound alone and in combination with rt-PA (3 micrograms/ml) was assessed with and without addition of Levovist (2 mg/ml). Loss in weight of each blood clot was used to measure the extent of thrombolysis. The number of thrombi in each group was between ten and 18. Experiments were carried out in sodium phosphate buffer, at a temperature of 37 degrees C, in a flow system with a flow rate of 15 ml/min.

The use of ultrasound alone showed a significant thrombolytic effect (41.8% weight loss), as compared to a control group (24.2%). The addition of Levovist further increased thrombolysis to 44.7%, which was not significant. However, in combination with rt-PA, ultrasound-mediated thrombolysis could be significantly increased from 65.8% to 74.2%, when Levovist was added (p < 0.05).

These data show that the thrombolytic efficacy of low-frequency continuous-wave ultrasound in combination with rt-PA is augmented in the presence of Levovist.