Sex Differences in Postoperative Recovery and Mortality After High‐Risk Cardiac Surgery: A Propensity Score–Matched Post Hoc Analysis of the SUSTAIN‐CSX Trial

Background Sex‐related differences after cardiac surgery remain controversial because women often present with higher baseline risk and complexity than men. We performed a post hoc propensity score–matched analysis of the SUSTAIN‐CSX (Sodium Selenite Administration in Cardiac Surgery) trial to evaluate sex differences in mortality, postoperative complications, and recovery after high‐risk cardiac surgery. Methods Of 1394 trial participants, 1386 had complete data. Women were matched 1:1 to men using nearest‐neighbor propensity score matching based on age and European System for Cardiac Operative Risk Evaluation II (EuroSCORE II), with exact matching on surgical category, yielding 327 female–male pairs. Prespecified sensitivity analyses adjusted for frailty, baseline hemoglobin, renal disease, left ventricular ejection fraction, previous myocardial infarction, preoperative medications, and baseline creatinine. Results In the primary matched analysis, 180‐day survival did not differ between women and men (log‐rank P =0.086; unadjusted hazard ratio, 1.80 [95% CI, 0.91–3.55]; P =0.091). In descriptive matched comparisons, women had numerically longer intensive care unit stay (median, 3 days [quartile 1, quartile 3 (Q1, Q3)=1, 6 days] versus 2 days [Q1, Q3=1, 5 days]) and hospital stay (median, 10 days [Q1, Q3=7, 18 days] versus 9 days [Q1, Q3=6, 16 days]; P =0.292), whereas major postoperative complications were similar. In adjusted sensitivity analyses accounting for the matched design and residual imbalance, female sex remained associated with longer intensive care unit stay (adjusted incidence rate ratio [IRR], 1.8 [95% CI, 1.2–2.9]; P =0.009) and hospital stay (adjusted IRR, 1.4 [95% CI, 1.0–1.9]; P =0.031). Mortality sensitivity analyses were model‐dependent. Conclusions In this propensity score–matched cohort of high‐risk cardiac surgery patients, women showed a longer postoperative recovery trajectory in adjusted analyses, whereas mortality findings were sensitive to model specification and should be interpreted cautiously. REGISTRATION URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02002247.