Abstract 4708: Rapid Resolution of ST Segment Elevation and Recovery of Function in Acute Myocardial Infarction Treated with Low Dose Intravenous Thrombolytics, Transthoracic Ultrasound, and Intravenous Microbubbles

Abstract

Rapid non-invasive methods of recanalizing acutely thrombosed coronary arteries and restoring microcirculatory flow are needed. Failure of ST segment elevation to resolve on the 12 lead electrocardiogram is a marker of microvascular no reflow, and occurs in over 30% of acute myocardial infarctions treated with primary percutaneous interventions. Transthoracic ultrasound (TTU) and intravenous (IV) microbubbles (MB) have the potential to increase epicardial recanalization (RC) when used with low dose thrombolytic therapy (TT). We hypothesized that this therapy may also dissolve microvascular thrombi, and thus improve microvascular recovery during treatment of an acute coronary thrombosis. In 45 closed chest pigs, acute left anterior descending (LAD) thromotic occlusions were created, followed by randomized treatment to either a) IV low dose TT alone (50,000 u/kg recombinant urokinase; n=15), or b) IV low dose TT combined with IV lipid encapsulated MB (ImaRx Therapeutics, Inc) and TTU (1.5 MHz diagnostic transducer using 1.9 MI therapeutic impulses applied only when low MI imaging detected MB within the affected risk area; n=30). Resolution of ST segment elevation as well as wall thickening (WT) within the central portion of the risk area were analyzed in pigs that had epicardial RC versus those that did not exhibit RC in the IV MB treated groups. Epicardial RC occurred within 60 minutes in 15 pigs (50%) treated with IV MB and TTU (p< 0.01 compared to IV TT alone;Table ). Significant >50% ST segment resolution occurred in over 90% of pigs with epicardial RC treated with TT and MB, but also in six of 15 pigs that did not have RC. In these six pigs, WT within the risk area increased similar to the pigs which had epicardial RC (Table ). Diagnostic TTU and IV microbubbles improve microvascular perfusion even if epicardial RC is not achieved, leading to rapid recovery of function. Both epicardial and microvascular reflow can be achieved with this technique. ST segment and WT Changes Before and Following Treatment