Echocardiography in experimentally-induced myocardial ischemia

Using an experimental canine model, we have employed echocardiography to study segmental dyskinesis produced by acute coronary occlusion. Characteristic alterations in posterior wall and septal motion occur after acute coronary ligation; these resemble clinical abnormalities described in acute and old myocardial infarction. The degree of dyskinesis produced is directly related to the severity of the perfusion deficit. Coronary reperfusion had variable effects on dyskinesis; most animals showed improvement but in some the myocardial contraction abnormalities became more severe. A vaviety of interventions were undertaken during ischemia. The elevated level of arterial pressure induced by the administration of methoxamine increased ventricular diameter and presumably oxygen requirements, and was deleterious to ischemic wall motion whereas the administration of norpinephrine reduced ventricular diameter and improved function. Intra-aortic balloon counterpulsation had little effect on either ischemic motion or perfusion. These experimental studies generally support conclusions drawn from clinical echocardiograms about the relationship of abnormalities of wall motion to coronary artery lesions and myocardial ischemia, and suggest further clinical uses for echocardiography in coronary disease.