[Echocardiography in superacute phase of myocardial infarction: an experimental study]

The significance and usefulness of two-dimensional echocardiography (2DE) in the evaluation of superacute phase of myocardial infarction were studied in 13 dogs with coronary occlusion, and 2DE findings were compared with the hemodynamic indices. Myocardial infarction was produced by the occlusion of anterior descending branch of the left coronary artery in 13 anesthetized adult mongrel dogs. In 6 dogs, the end-diastolic area and percent fractional shortening (%FS) in each short-axis view of the left ventricle at the level of the mitral valve, chordae tendineae, papillary muscles, low papillary muscles and apex were measured during 60 minutes, and end-diastolic wall thickness of infarct area situated in the transitional zone between the septum and the anterior wall were compared with that of non-infarct area immediately and subsequent 60 minutes after occlusion. Positive dP/dt/P, time constant T and cardiac output were measured simultaneously with an echocardiographic study. Severe enlargement and expansion of the left ventricular cavity (ballooning) and a decrease of %FS and thinning of the left ventricular wall perfused by the occluded artery occurred immediately after occlusion and persisted during subsequent 60 minutes. Time constant T was significantly prolonged, while positive dP/dt/P and cardiac output were decreased immediately and continued up to 60 minutes after occlusion. 2DE findings corresponded well with the changes of cardiac function and hemodynamics determined simultaneously. We concluded that the detection of the left ventricular ballooning is important in the diagnosis of superacute phase of myocardial infarction in dogs.