Bilateral internal mammary artery grafting reverses the negative influence of gender on outcomes of coronary artery bypass grafting surgery

Abstract

Objectives: Coronary artery bypass grafting (CABG) has historically demonstrated higher hospital mortality in women compared with men. The influence of gender on long-term outcomes has not been clearly defined.

Methods: A retrospective analysis of 4584 consecutive CABG patients was conducted: 3647 men (1761 single internal mammary artery, [SIMA]; 1886 bilateral IMA, [BIMA]) and 937 women (608 SIMA and 329 BIMA). Propensity-score analysis and optimal matching algorithms were used to create matched groups for baseline risk factors between men and women (SIMA: 602 men and 602 women; BIMA: 328 men and 328 women). Cross-sectional follow-up (6 weeks to 32.1 years; mean 12.8 years) was 96.7% complete.

Results: Hospital mortality was higher in unmatched female vs male patients (SIMA 36/608; 5.9 vs 72/1761; 4.1%; BIMA 11/329; 3.3 vs 47/1886; 2.5%; P = 0.010). However, in the matched groups the increased hospital mortality for females approached statistical significance in the SIMA but not in the BIMA patients. (SIMA male 21/602, 3.5%; female 35/602, 5.8%; P = 0.055; BIMA male 12/328; 3.7%; female 11/328; 3.4%; P = 0.832). When propensity matched for baseline variables, the female SIMA patients experienced prolonged survival compared with their male counterparts. (male vs female, 20-year survival 17.0 ± 2.0 vs 26.4 ± 2.3%; median 10.4 vs 11.4; P = 0.043.) However, long-term survival between the matched male and the female BIMA patients was comparable (male vs female, 20-year survival 31.3 ± 3.6 vs 30.1 ± 3.6%; median 13.7 vs 13.7; P = 0.790).

Conclusions: When liberally applied, BIMA grafting ameliorates both the increased perioperative mortality in female patients and the reduced long-term survival of male patients, effectively reversing the negative influence of gender on both short- and long-term outcomes of CABG surgery.

Keywords: Arterial grafts; Coronary artery bypass grafting; Internal mammary artery; Propensity matching; Women.