In vitro ultrasound augmented clot dissolution - What is the optimal timing of ultrasound application?

Summary. The mechanism of ultrasound augmentation of pharmacological thrombolysis is yet unknown. The goal of this study is to find the best timing regimen for in-vitro ultrasound augmented clot dissolution by streptokinase, heparin and their combination. Blood clots from 4 donors were cut into 200-400 mg sections and randomized to no treatment with ultrasound; pre-treatment with ultrasound (before immersion); early treatment with ultrasound; or late treatment with ultrasound. Clots were placed in tubes containing either saline; heparin; streptokinase or streptokinase+heparin. All groups showed significant weight reduction (p<0.001). Using the one way ANOVA test, we showed that ultrasound application resulted in a significantly higher rate of clots dissolution (p<0.05) than without ultrasound in all of the solutions tested. We found no statistically significant difference between the three ultrasound regimens tested. In conclusion, in our in-vitro model, no single ultrasound timing schedule was found to provide better clot dissolution than the other schedules. This finding may suggest an additive effect between the ultrasound and the different solutions rather than a synergistic effect.