Timing of coronary revascularization after acute myocardial infarction. Early and late results in patients revascularized within seven weeks

Abstract

Evidence of ischemia after acute myocardial infarction is a serious complication. If angiography reveals significant coronary artery disease, the precise timing of myocardial revascularization may be of critical importance. From 1978 through 1982, 174 patients underwent myocardial revascularization within 7 weeks of a documented myocardial infarction. The male:female ratio was 138:36, the average age was 58 +/- 1 (SEM) years; and the ejection fractions averaged 41% +/- 1%. Forty-four (25%) patients required preoperative intra-aortic balloon pump support, and an additional 18 (10%) required intra-aortic balloon pumping to be separated from cardiopulmonary bypass. An average of 2.9 +/- 0.1 vessels per patient were bypassed. The hospital mortality for these 174 patients was 16%. When mortalities were categorized according to the postinfarction week in which operation was performed, hospital mortality fell from 46% for those patients operated upon within 1 week of infarction to 6% for those patients operated upon 7 weeks after infarction. Of those patients operated upon within the first week after infarction, 23% were in cardiogenic shock and 62% required preoperative balloon pumping. Clearly the most critically ill patients were operated upon during the early postinfarction period. However, there was a marked difference in survival when patients in each of the seven weekly groups were classified according to ejection fraction. All patients with an ejection fraction greater than or equal to 50% (50 patients) operated upon at any time after infarction survived their hospital course, with only one late death. Conversely, among the 124 patients with an ejection fraction less than 50% operated upon during this 7 week interval, there were 27 (22%) hospital deaths. In this latter group, survival rates steadily improved if revascularization was performed at a time more remote from the infarction. The difference in early and late survival rates of patients operated upon with an ejection fraction greater than or equal to 50% compared to patients with an ejection fraction less than 50% is highly significant (p less than 0.001). We conclude that myocardial revascularization is safe at any time after myocardial infarction for those individuals with an ejection fraction greater than or equal to 50%. However, if the ejection fraction is less than 50%, then operation after myocardial infarction should be delayed at least 4 weeks.