Effects of intravenous metoprolol on global and regional left ventricular function after coronary arterial reperfusion in acute myocardial infarction

The American Journal of Cardiology
R M SteingartS Katz

Abstract

Coronary reperfusion in myocardial infarction improves infarct zone motion, but its effect on the global ejection fraction has been less consistent. The directional movement of the ejection fraction is determined by the opposing influences of improved infarct zone motion and diminishing hyperkinesia in the noninfarct zone. Noninfarct zone hyperkinesia has been attributed to catecholamine stimulation, the Frank-Starling mechanism or intraventricular interactions that unload noninfarcted segments. To investigate the influence of catecholamine stimulation, 9 men presenting with a first myocardial infarction (mean age 53 +/- 13 years) were studied. Coronary reperfusion was accomplished less than 4 hours after the onset of myocardial infarction. Radionuclide ventriculography was then performed before and immediately after the intravenous administration of 15 mg of metoprolol. End-diastolic volume did not change, but end-systolic volume increased 28% after metoprolol (p = 0.041). The ejection fraction decreased from 55 +/- 13% before metoprolol to 45 +/- 14% after its administration (p = 0.002). There was no effect of intravenous metoprolol on infarct zone motion, whereas motion in the noninfarcted segment decreased (p = 0.002). The ...Continue Reading

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