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Mortality and morbidity after coronary artery bypass surgery related to pre-operative left ventricular ejection
O Risum1, S Nitter-Hauge, M Abdelnoor
1Surgical Department A, Rikshospitalet, Oslo, Norway.
Insights
A low left ventricular ejection fraction (LVEF) significantly increases early mortality risk after coronary artery bypass grafting. Reduced LVEF also correlates with higher late mortality, but not recurrent angina or non-fatal myocardial infarction.
Area of Science:
- Cardiology
- Cardiac Surgery
- Clinical Outcomes Research
Background:
- Left ventricular ejection fraction (LVEF) is a key indicator of cardiac function.
- Pre-operative LVEF assessment is crucial for risk stratification in patients undergoing coronary artery bypass grafting (CABG).
Purpose of the Study:
- To determine if pre-operative left ventricular ejection fraction levels predict early and late mortality.
- To assess the association between LVEF and the risk of recurrent angina pectoris and late non-fatal myocardial infarction following CABG.
Main Methods:
- A cohort of 934 patients undergoing CABG were analyzed.
- Patients were stratified into four LVEF groups: <=40%, 41-60%, 61-80%, and >80%.
- Relative risks for mortality and adverse cardiac events were calculated using chi-square tests, with survival curves for cumulative survival analysis.
Main Results:
- Patients with LVEF <=40% had a significantly higher risk of early mortality (Relative Risk [RR] = 10.2) and late mortality (RR = 3.6).
- A near-linear increase in late mortality risk was observed with decreasing LVEF values.
- No significant difference in the risk of recurrent angina pectoris or late non-fatal myocardial infarction was found across LVEF groups.
Conclusions:
- Pre-operative LVEF <=40% is a strong predictor of increased early mortality risk in CABG patients.
- Lower LVEF values are associated with a progressively higher risk of late mortality after CABG.
- LVEF does not appear to be a significant predictor for recurrent angina or non-fatal myocardial infarction post-CABG.
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.
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