Uncovering Sex-Related Differences in Cerebrovascular Bypass Patency: An Institutional Review of 357 Direct Bypasses

IntroductionDemographics and comorbid conditions play a role in vascular health, yet their specific impact on cerebrovascular bypass patency remains unclear. MethodsAn institutional database of 357 patients with intracranial bypass procedures between 08/2001-05/2022 was retrospectively reviewed. Patients with bypass for all causes (e.g., aneurysm, atherosclerotic disease, Moyamoya disease) were included. Medical history, surgical technique, and flow-related measurements (intraoperatively and on quantitative MRA at follow-up) were compared across biological sex and in relation to bypass patency. ResultsOf 357 patients, 141 were male (39.5%) and 216 were female (60.5%) with average age 49.0+/-16.7. Bypass patency at last follow-up was 84.4% for men vs. 69.2% for women (p=0.001). Significant differences were seen in underlying diagnoses, with more aneurysm and Moyamoya cases represented in female sex (p<0.001); irrespective of diagnosis, lower patency rates were seen in women when considering bypass for aneurysm (p=0.032), Moyamoya disease (p=0.035), and for atherosclerotic disease (p=0.159). Medical comorbidities were seen at higher rates in men, with comorbidity score 2.7 vs. 2.1 (p<0.001). Cut flow was higher in men 59.2 vs. 51.1 (p=0.028), but no significant differences were seen in intraoperative bypass flow, cut flow index (CFI), or follow-up QMRA. After removing cases using interposition grafts, similar differences were redemonstrated. Propensity score matched analysis found females have a 2.71 higher chance of bypass occlusion after adjusting for CFI (p=0.017, 95% CI: 1.19-6.18). ConclusionBiological sex appears to play a significant role in bypass patency, across diagnoses. Women were significantly less likely to have patent bypasses at last follow-up, despite having less medical comorbidities than men and despite having similar intraoperative and perioperative flows. Further study is required to better elucidate the influence of sex on long-term bypass patency.