Ultrasound accelerates thrombolysis of acutely induced platelet-rich thrombi similar to those in acute myocardial infarction.

BACKGROUND

Although sonothrombolysis has been studied for development of recanalization that is safer and more efficacious than the methods currently used, there have been no studies of the efficacy of sonothrombolysis for the platelet-rich thrombi that typically cause acute myocardial infarction (AMI). The effects of adding ultrasound (US) to pharmacological lysis of platelet-rich thrombi was examined in a rabbit model of femoral artery occlusion.

METHODS AND RESULTS

In 35 rabbits, the right femoral artery was balloon-injured repeatedly at 4-week intervals to induce platelet-rich thrombi. Two hours after the induction of occlusive thrombi, 27,500 IU/kg tissue plasminogen activator (tPA) were injected via an ear vein, with or without transcutaneous US (continuous wave, 1 MHz, 0.75 W/cm2), or 13,750 IU/kg tPA was administered with US (n=10). Significantly higher rates of successful thrombolysis (Thrombolysis In Myocardial Infarction grade 3) were observed with US (90.0%) than without it (10.0%), irrespective of the dose of tPA used (p<0.01). The peak flow velocity in affected femoral arteries was significantly higher with US (p<0.01), and histological examination confirmed complete dissolution of thrombi. However, the thrombi were not affected by US alone (n=5).

CONCLUSIONS

US facilitates thrombolysis of platelet-rich thrombi and could be a useful component of thrombolytic therapy following AMI.