Non-invasive assessment of left ventricular function and prognosis in acute myocardial infarction--clinical significance of B-B' step of the mitral valve in M-mode echocardiography.

On 37 patients with acute myocardial infarction (AMI), M-mode echocardiography was performed sequentially from the onset of the disease for more than 20 days in order to study the significance of a B-B' step of the anterior mitral valve in AMI. The following results were obtained: 1) A B-B' step was observed in 60% of the patients studied, and the incidence was higher in antero-septal than postero-inferior infarction. 2) A B-B' step was especially noticed in the patients who had left ventricular failure. 3) The prognosis of the patients with a B-B' step was worse than that of the patients without it. A B-B' step, which either persisted for longer than 10 days of developed into a more definite form with the course of time, was a sign of an unfavorable prognosis. 4) The patients with a B-B' step had higher mean pulmonary arterial pressure than the patients without it. These results suggest that serial observations of the B-B' step in patients with AMI were a useful means to evaluate the left ventricular function and to determine prognosis in this disorder.