High mortality after coronary bypass surgery in patients with high-grade left main coronary artery stenosis

OBJECTIVE: To determine mortality after coronary artery bypass grafting (CABG) in relation to degree of left main coronary artery (LMCA) obstruction. DESIGN: All patients without LMCA stenosis (n=3370), with low-grade stenosis (n = 261), high-grade stenosis (n = 224) or total occlusion of the LMCA (n = 15) were followed for ten years after CABG performed during 1970-1989. RESULTS: Early mortality was 1.9% and 2.3%, respectively, if there was no or a low-grade LMCA stenosis vs. 6.3% if the stenosis was high-grade. Ten-year survival was 76% if no LMCA obstruction, 74% if low-grade stenosis and 64% if the stenosis was high-grade. Risk of early death (odds ratio 2.6, 95% CI 1.4-4.8) and mortality at ten years (relative risk 1.5, 95% CI 1.1-2.0) was higher in patients with high-grade stenosis than in those without LMCA stenosis. There was no increased long-term mortality in patients with low-grade stenosis or among the few patients with occlusion of the LMCA. CONCLUSIONS: High-grade LMCA stenosis was associated with a three-fold increased risk of early and fifty percent higher risk of late death than in patients without LMCA stenosis.