Propensity-matched study of single versus bilateral internal mammary artery grafting in women undergoing coronary bypass surgery

BACKGROUND The optimal second conduit in coronary artery bypass grafting (CABG) remains debated, particularly in women, for whom long-term sex-specific evidence is limited. We compared outcomes after bilateral internal mammary artery (BIMA) grafting versus left internal mammary artery plus saphenous vein grafting. METHODS This retrospective study included 1,686 women undergoing CABG with at least 2 grafts: 1,441 received left internal mammary artery plus saphenous vein grafts and 245 received BIMA. Propensity score matching produced 239 well-balanced pairs. In-hospital outcomes and long-term survival were evaluated using Kaplan-Meier analysis, log-rank testing, and Cox regression. RESULTS Before matching, women receiving left internal mammary artery plus saphenous vein grafts were older and had higher rates of diabetes and extensive coronary disease. In-hospital outcomes were comparable. Unmatched 20-year survival was 79.1% versus 85.8% (P=.200). After matching, survival remained similar, although numerically favoring BIMA (P=.800). Grafting strategy did not independently predict mortality (hazard ratio, 0.739; 95% confidence interval, 0.476-1.148; P=.178). Increasing age, diabetes, advanced heart failure symptoms, previous myocardial infarction, and previous cardiac surgery were independently associated with reduced long-term survival. CONCLUSIONS BIMA grafting was safe and associated with perioperative and long-term outcomes comparable with left internal mammary artery plus saphenous vein grafting. Although survival numerically favored BIMA, no statistically significant advantage was demonstrated. These findings support individualized conduit selection, with BIMA remaining a reasonable option for carefully selected women.