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 ejectionfraction that may be indicative of an increased risk of earlyand late mortality and of recurrent angina pectoris and latenon-fatal myocardial infarction. MATERIAL AND METHODS: A total of 934 patients with known left ventricular ejectionfraction, 80 women and 854 men, were submitted to coronary arterybypass grafting at the Cardiovascular Unit of Rikshospitalet,Oslo, between August 1982 and December 1986. The closing datewas the 1st of January 1993, with a mean follow-up of time of7·4 years. The patients were divided in to four subgroupsaccording to their level of left ventricular ejection fraction:40%, 41–60%, 61–80% and >80%. The left ventricularejection fraction varied from 13–98%. A chi-square testof linear trend was used to calculate the relative risk betweenthe different subgroups. Cumulative survival was determinedusing survival curves. RESULTS: Early mortality. Twenty-five patients (2·7%) died within30 days of operation. Patients with left ventricular ejectionfraction 40% had a relative risk of 10·2 (1·9–17·2),for left ventricular ejection fraction 41–60% the relativerisk was 0·9 (0·1–8·9) and for leftventricular 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 patientswith left ventricular ejection fraction 40% the relative riskwas 3·6 (2·8–10·9), for left ventricularejection fraction 41–60% the relative risk was 1·8(1·1–3·6),and for left ventricular ejectionfraction 61–80% the relative risk was 1·5 (0·9–2·8).Recurrent angina pectoris. A total of 138 patients developedrecurrent angina pectoris during the follow-up period, givingan incidence of 14·8%. Here, for left ventricular ejectionfraction 40% the relative risk was 0·5(0·2–13), for left ventricular ejection fraction 41–60% therelative risk was 1·0 (0·5–1·8) andfor left ventricular ejection fraction 61–80% the relativerisk was 1·2 (0·7–2·0). Late non-fatalmyocradial infarction. Altogether, 90 patients (9·6%)experienced non-fatal myocardial infarction in the late phase.For left ventricular ejection fraction 40% the relative riskwas 0·6(1·2–1·8), for left ventricularejection fraction 41–60% the relative risk was 1·0(0·5–2·0) and for left ventricular ejectionfraction 61–80% the relative risk was 0·7 (0·41–1·3).Cumulative survival. When pooled together, the cumulative survivalfor 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 ejectionfraction 40% cumulative survival was 87·5, 73·1and 55·2%, respectively. CONCLUSION: When the left ventricular ejection fraction was 40% or lower,there was a substantial increase in the risk of early mortalityin patients submitted to coronary artery bypass grafting. Asfor the risk of late mortality, there was a practically linearincrease in risk with falling values of left ventricular ejectionfraction. We found no difference in risk of developing recurrentangina pectoris or of late non-fatal myocardial infarction relatedto values of left ventricular ejection fraction.