Determinants of Cardiac Failure after Coronary Bypass Surgery within 30 Days of Acute Myocardial Infarction

Abstract

Timing of coronary artery bypass grafting after acute myocardial infarction (MI) is controversial, especially if myocardial function is depressed. Early coronary artery bypass grafting may result in reperfusion injury causing cardiac failure. Delay, however, may risk a second ischemic event. This study was performed to determine if four preoperative factors—time after MI, ejection fraction, ischemia (need for intravenous administration of nitroglycerin), and failure (need for inotropic support)—independently predict postoperative cardiac failure. Postoperative failure was defined as the need for inotropic support or intraaortic balloon pumping. The study group consisted of 145 patients who underwent isolated coronary artery bypass grafting between January, 1980, and July, 1985, within 4 weeks of an acute MI. Postoperatively 38 patients (26%) had cardiac failure. Five patients, all of whom had postoperative cardiac failure, died. Univariate and stepwise logistic regression analyses showed preoperative failure ( p = .0001), ejection fraction less than 45% ( p = .002), and preoperative ischemia ( p = .02) were predictors of postoperative cardiac failure. Time after MI was not found to be an independent predictor ( p = .96). We conclude that if ischemia or threatening coronary anatomy is present early after MI and clinical improvement is not occurring, operative intervention should be strongly considered at that time, as it does not appear that delay itself reduces the risk of cardiac failure and may risk a second ischemic event.