Survival after bilateral internal mammary artery in coronary artery bypass grafting: Are women at risk?

Background: Most observational studies support long-term survival benefit after bilateral internal mammary artery (BIMA) compared with single internal mammary artery (SIMA) coronary artery bypass grafting (CABG) but data on females is scarce. We compared survival and safety of BIMA versus SIMA CABG between males and females at our tertiary care center.
Methods: Single-center retrospective cohort including consecutive patients with at least 2 left-coronary system (LCS) vessel disease who underwent isolated CABG with at least 1 IMA conduit and a minimum of 2 conduits targeting the LCS in 2004-2013. All-cause mortality was the primary outcome, secondary outcomes were early mortality and reoperation due to sternal wound complications (SWC). Kaplan-Meier analysis after inverse probability weighting using propensity score (IPW) was used to compare BIMA and SIMA CABG amongst genders. Results were confirmed in subgroup analysis.
Results: BIMA CABG was performed in 39% out of 2424 eligible procedures and in 27% of 460 females. No differences were found in survival after BIMA and SIMA CABG (median and maximum follow-up of 5.5 and 12 years, respectively) but a statistical interaction was observed with gender (P < 0.001). Females who underwent BIMA CABG showed higher mortality (weighted HR in females subset: 3.16; 95% CI: 1.56-6.29, P = 0.001). BIMA CABG showed a higher incidence of reoperation due to SWC (IPW adjusted model OR: 1.74; 95% CI: 1.16-2.60) that was mostly ascribable to males (weighted OR in males: 3.10; 95% CI: 1.74-5.51, P < 0.001).
Conclusions: Females may experience higher mortality after BIMA CABG which should be further explored.
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