Coronary and microvascular thrombolysis with guided diagnostic ultrasound and microbubbles in acute ST segment elevation myocardial infarction.

BACKGROUND

During a microbubble infusion, guided high-mechanical index impulses from a diagnostic two-dimensional transducer improve microvascular recanalization in acute ST-segment elevation myocardial infarction. The purpose of this study was to further elucidate the mechanism of improved microvascular flow in normal and hyperlipidemic atherosclerotic pigs.

METHODS

In 14 otherwise normal pigs, acute left anterior descending thrombotic coronary occlusions were created. Pigs subsequently received aspirin, heparin, and half-dose fibrinolytic agent (tenecteplase or tissue plasminogen activator), followed by randomization to either no additional treatment (group I) or a continuous infusion of nontargeted microbubbles and guided high-mechanical index impulses from a three-dimensional transducer (group II). Epicardial recanalization rates, ST-segment resolution, microsphere-derived myocardial blood flow, and ultimate infarct size using myocardial contrast echocardiography were compared. The same coronary thrombosis was created in a set of 12 hypercholesterolemic pigs, which were then treated with the same pharmacologic and ultrasound regimen (group III, n = 6) or the pharmacologic regimen alone (group IV, n = 6).

RESULTS

Epicardial recanalization rates in groups I and II were the same (29%), but peri-infarct myocardial blood flow and ultimate infarct size improved after treatment in group II (P < .01 vs group I). In group III, epicardial recanalization was 100% (vs. 50% in group IV), and there were significant reductions in ultimate infarct size (P = .02 compared with group IV).

CONCLUSIONS

Guided high-mechanical index impulses from a diagnostic transducer and nontargeted microbubbles improve peri-infarct microvascular flow in acute ST-segment elevation myocardial infarction, even when epicardial recanalization does not occur.