Therapeutic Use of Ultrasound in Acute Coronary Artery Disease

In acute coronary artery disease, pre-clinical studies have indicated that, during a continuous infusion of intravenous perfluorocarbon containing microbubbles, the ultrasonic power delivered from a diagnostic ultrasound transducer is capable of restoring microcirculatory flow and improving epicardial recanalization rates obtained by conventional therapy, a process known by Sonothrombolysis. Since both diagnostic ultrasound and intravenous infusions of microbubbles are a Class I indication to assess regional and global left ventricular function and risk area in patients with ST segment elevation myocardial infarction (STEMI). The investigators propose to examine the effectiveness of microvascular sonothrombolysis.

A total of 100 patients with acute STEMI will be randomized to receive diagnostic ultrasound guided high mechanical index (MI) impulses in different approaches applied within and outside the risk area during a continuous infusion of intravenous 3% Definity® or placebo. The different ultrasound regimens are: Group I - a custom designed high mechanical index (MI) impulses at 4-20 usec and >1.0 MI designed for the 1.7 MHz S5-1 transducer; Group II - repeated diagnostic high MI impulses (all <2 usec pulse duration; MI=1.0 whenever very low MI perfusion imaging detected microbubbles within the microvasculature; Group III (control), where a few limited diagnostic high MI impulses (n<5 per patient) will be applied to assess myocadial perfusion before and after percutaneous coronary intervention (PCI). All patients will receive the conventional PCI approach, including 325 milligrams Aspirin, 600 milligrams Clopidogrel, and heparin bolus (5000 units), followed by primary PCI using glycoprotein 2b/3a inhibitors as anti-thrombotic agents using established protocols. Besides angiographic recanalization rates at the time of presentation to the catheterization laboratory, the patients will have a magnetic resonance exam performed at 72-96 hours post infarcton to quantify the myocardial salvagability index. Quantitative assessments of ejection fraction will be made at this time as well.Overall survival (OS), defined as the time from the start of treatment to death from any cause, will be evaluated.Comparisons between the three groups will be made on door to dilation times, survival, angiographic recanalization rates (ARR) at initial angiography, and reduction in infarct size determined by the salvagability index (SI) at magnetic resonance imaging 72-96 hours post STEMI. Left ventricular function and perfusion parameters by echocardiography will also be evaluated during, at 72-96 hours and at 6 months in all subjects.