MYOCARDIAL PERFUSION CHARACTERISTICS AND HEMODYNAMIC PROFILE OF MRX-115, A VENOUS ECHOCARDIOGRAPHIC CONTRAST AGENT, DURING ACUTE MYOCARDIAL-INFARCTION

We sought to determine whether MRX-115, a new venous echocardiographic contrast agent, could accurately assess risk area during coronary occ lusion and infarct size after reperfusion by using novel imaging modal ities meant to selectively enhance contrast signals. In 12 open-chest dogs, venous injections of 0.5 ml of MRX-115 were performed during bas eline and coronary occlusion and after reperfusion in the presence of exogenous hyperemia. Ultrasound was transmitted at 2 MHz and received at both 2 MHz (fundamental) and 4 MHz (harmonic) frequencies during co ntinuous and intermittent (end-systolic only) imaging. The risk area d uring coronary occlusion was compared with technetium autoradiography, and the infarct size after reperfusion was compared with postmortem t issue staining. MRX-115 produced no alterations in hemodynamic or pulm onary gas exchange at any stage. During continuous (both fundamental a nd harmonic) and intermittent fundamental imaging, measurements of per fusion defects were precluded in many dogs by either poor signal enhan cement or posterior wall attenuation. By comparison, these measurement s were possible during intermittent harmonic imaging in all dogs excep t one, which had a very small infarction during reflow. Correlation an alysis between perfusion defect size on intermittent harmonic imaging and either autoradiographic risk area or postmortem infarct size gave r values of 0.83 and 0.92, respectively. We conclude that MRX-115 is h emodynamically well tolerated and, when imaging is performed after ven ous injection, can accurately assess regions of hypoperfusion when com bined with intermittent harmonic imaging. These results are promising for the use of this approach in patients with acute myocardial infarct ion.