Noninvasive transcutaneous ultrasound augments thrombolysis in the left circumflex coronary artery--an in vivo canine study.

BACKGROUND

Ultrasound has the potential to augment chemical thrombolysis.

METHODS AND RESULTS

Thrombotic occlusions in the left circumflex artery (LCx) were induced in 27 dogs. Sixty minutes later, tissue-type plasminogen activator (t-PA) was given intravenously over 90 min. Thrombotic occlusions (n = 20) were treated with concomitant transcutaneous low frequency (27 kHz), continuous wave (CW) (n = 10) or pulsed wave (PW) (n = 10) ultrasound. Tissue-type plasminogen activator plus ultrasound (n = 20) vs. tissue-type plasminogen activator alone (n=7) resulted in more frequent Thrombolysis in Myocardial Infarction (TIMI) 3 flow (90% vs. 43%, P = 0.024) and less reocclusion (11% vs. 67%, P = 0.080). At 60 min, median TIMI grade flow for tissue-type plasminogen activator alone was 2 (mean: 1.43 +/- 1.40) compared to 3 (mean: 2.70 +/- 0.95) for tissue-type plasminogen activator plus continuous as well as pulsed wave ultrasound (P = 0.035). Continuous wave and pulsed wave ultrasound were equally effective in augmenting thrombolysis. Histologically, no ultrasound-mediated injury to the myocardium or coronary arteries occurred.

CONCLUSION

Both transcutaneous low frequency continuous wave ultrasound and pulsed wave ultrasound enhance tissue-type plasminogen activator-mediated thrombolysis of the posterior circulation with higher TIMI 3 flow rates and less reocclusion than with tissue-type plasminogen activator alone. In addition, at the energy levels used, low frequency ultrasound appears safe.