Sex-specific differences in coronary blood flow dynamics during coronary artery bypass surgery

Women are known to experience worse outcomes compared to men following coronary artery bypass grafting (CABG). The goal of this study was to identify and analyze potential differences in intraoperative flow dynamics during CABG. The primary objective was to compare transit time graft flow measurements (TTFM) during isolated CABG between sexes. To ensure the integrity of TTFM data specific to the LITA-LAD anastomosis, patients with composite LITA graft configurations were excluded, yielding 317 males and 69 females. To ensure comparable baseline characteristics between men and women, propensity score matching was performed followed by entropy balancing, yielding 69 propensity matched pairs. After balancing, mean flow was comparable between females and males respectively (47.0 ml/min [35.0,63.0] vs. 44.0 ml/min [35.0,60.0], p = 0.98), as well as the pulsatility index (2.3 [2.1–3.3] vs. 2.7 [1.8,3.0], p = 0.88), and backflow (0.70% [0.40,2.10] vs. 1.70% [0.20,5.00], p = 0.98). However, the diastolic filling was significantly lower in women than men (68.8% [65.8,72.7] vs. 79.4% [70.6,81.3], p = 0.01). In weighted linear regression analysis, women had a significantly lower diastolic filling compared to men with an estimate of -5.17 (95%CI [-8.84,-2.58], p < 0.001). No significant intersex differences were observed for other TTFM parameters. Females undergoing isolated CABG exhibited a significantly lower diastolic filling compared to men by intraoperative TTFM. No other TTFM differences were observed, suggesting similar grafting outcomes. These findings support the hypothesis that coronary microvascular dysfunction may play a critical role in intersex disparities in CABG outcomes.