Mortality and morbidity after coronary artery bypass surgery related to pre-operative left ventricular ejection fraction: a follow-up study.

OBJECTIVE To study the pre-operative level of left ventricular ejection fraction that may be indicative of an increased risk of early and late mortality and of recurrent angina pectoris and late non-fatal myocardial infarction. MATERIAL AND METHODS A total of 934 patients with known left ventricular ejection fraction, 80 women and 854 men, were submitted to coronary artery bypass grafting at the Cardiovascular Unit of Rikshospitalet, Oslo, between August 1982 and December 1986. The closing date was the 1st of January 1993, with a mean follow-up of time of 7.4 years. The patients were divided in to four subgroups according to their level of left ventricular ejection fraction: < or = 40%, 41-60%, 61-80% and > 80%. The left ventricular ejection fraction varied from 13-98%. A chi-square test of linear trend was used to calculate the relative risk between the different subgroups. Cumulative survival was determined using survival curves. RESULTS Early mortality. Twenty-five patients (2.7%) died within 30 days of operation. Patients with left ventricular ejection fraction < or = 40% had a relative risk of 10.2 (1.9-17.2), for left ventricular ejection fraction 41-60% the relative risk was 0.9 (0.1-8.9) and for left ventricular ejection fraction 61-80% the relative risk was 2.8 (0.6-17.2). Left ventricular ejection fraction > 80% was defined as relative risk = 1. Late mortality. Altogether, 174 patients died in the late phase (18.6%). For patients with left ventricular ejection fraction < or = 40% the relative risk was 3.6 (2.8-10.9), for left ventricular ejection fraction 41-60% the relative risk was 1.8 (1.1-3.6), and for left ventricular ejection fraction 61-80% the relative risk was 1.5 (0.9-2.8). Recurrent angina pectoris. A total of 138 patients developed recurrent angina pectoris during the follow-up period, giving an incidence of 14.8%. Here, for left ventricular ejection fraction < or = 40% the relative risk was 0.5 (0.2-1.3), for left ventricular ejection fraction 41-60% the relative risk was 1.0 (0.5-1.8) and for left ventricular ejection fraction 61-80% the relative risk was 1.2 (0.7-2.0). Late non-fatal myocardial infarction. Altogether, 90 patients (9.6%) experienced non-fatal myocardial infarction in the late phase. For left ventricular ejection fraction < or = 40% the relative risk was 0.6 (1.2-1.8), for left ventricular ejection fraction 41-60% the relative risk was 1.0 (0.5-2.0) and for left ventricular ejection fraction 61-80% the relative risk was 0.7 (0.41-1.3). Cumulative survival. When pooled together, the cumulative survival for patients with left ventricular ejection fraction > 40% was 95.9, 91.9 and 79% after 1, 5 and 10 years, respectively. For the patients with left ventricular ejection fraction < or = 40% cumulative survival was 87.5, 73.1 and 55.2%, respectively. CONCLUSION When the left ventricular ejection fraction was 40% or lower, there was a substantial increase in the risk of early mortality in patients submitted to coronary artery bypass grafting. As for the risk of late mortality, there was a practically linear increase in risk with falling values of left ventricular ejection fraction. We found no difference in risk of developing recurrent angina pectoris or of late non-fatal myocardial infarction related to values of left ventricular ejection fraction.