Long-term survival after coronary artery bypass grafting comparing bilateral versus single internal mammary artery in a women cohort

Abstract Introduction Although neutral results from the ART randomized controlled trial, observational studies have been supporting better survival after bilateral internal mammary artery (BIMA) vs single internal mammary artery (SIMA) coronary artery bypass grafting (CABG). However, for some specific subgroups, like women patients, more doubts remain about BIMA benefits. Aim To compare long-term survival and early results in women after SIMA vs BIMA. Methods Longitudinal, retrospective, single-center study including consecutive women with at least 2 left-coronary system (LCS) vessel disease who underwent primary isolated CABG with at least 1 internal mammary artery (IMA) conduit and a minimum of 2 conduits targeting the LCS, between 2004-2014. Emergent or salvage surgeries, on-pump beating-heart, BIMA in which 1 IMA targeted the right coronary artery territory were excluded. The primary outcome was all-causes mortality (checked on February 2023). Time-to-event outcomes were studied using Kaplan-Meier Curves, Log-Rank test and multivariable Cox Regression. Median follow-up was 11 years, maximum of 19 years. Results From 539 women selected for this study, BIMA CABG was performed in 30%. SIMA patient’s were older (mean age 68.95±8.39 vs 62.75±9.82 years, p<0.001), but the prevalence of cardiovascular risk factors were similar between groups (arterial hypertension, p=0.693; dyslipidemia, p=0.111; diabetes mellitus, p=0.462 and obesity, p=0.109). Peripheral artery disease (p=0.707), left ventricular dysfunction (p=0.727), cerebrovascular disease (p=0.730), active smoking habits (p=0.05) and chronic obstrutive pulmonary disease (p=0.537) were also similar. Severe chronic kidney disease (27% vs 14%, p<0.001) and Canadian Coronary Society - grade IV (74% vs 63%, p=0.011) were more frequent in SIMA group. In the univariable survival analysis, SIMA had worse survival results than BIMA (Log Rank test p<0.01). At 5-, 10- and 15- years of follow-up, cumulative survival for SIMA vs BIMA were 88% vs 90%, 68% vs 75%, 42% vs 58%, respectively. However, the multivariable Cox regression showed that BIMA was not associated with long-term survival (HR [95%CI]: 1.09 [0.75-1.59], p=0.6). Most of post-operative outcomes were similar between groups, with the exception of atrial fibrilation (25% vs 16%, p=0.031) and time to discharge (median days [min-max]: 7 [4-128] vs 7 [4-59]) that were higher in SIMA. No differences were found in immediate reexploration of thorax (sternal infection – 0.3% SIMA vs 1.2% BIMA, p=0.219; bleeding- 1.6% SIMA vs 0.6% BIMA, p=0.681). Redo CABG occurred in 1 SIMA and 1 BIMA women, at 41 and 84 months of follow-up, respectively. Conclusion In this study, revascularization with BIMA seems to be safe in women and provides similar results than SIMA. More studies in women are needed to establish the better approach for this specific subgroup.