Abstract Backgrounds Isolated tricuspid valve surgery (ITVS) is considered a high-risk procedure. Right ventricular (RV) size plays a critical role in the prognosis of ITVS patients. The effect of sex differences in the degree of right ventricular(RV)dilatation in ITVS patients has not been established. Purpose The primary objective of this study was to assess in-hospital major adverse events (AEs) following ITVS in women compared with men on the basis of preoperative RV size measured by 3D echocardiography. Methods Consecutive patients undergoing ITVS were identified from a prospectively maintained database.Transthoracic echocardiography was performed the day before ITVS. In-hospital AEs were defined as one of the following occurring before discharge: death, shock, acute renal failure requiring dialysis, or prolonged (>72h) mechanical ventilation. 3D RV parameters including end-diastolic volume (EDV), end-systolic volume (ESV), EDVi (indexed by body surface area), ESVi (indexed by body surface area) and ejection fraction (EF) were calculated using commercially available software. Comparison of the adjusted odds ratios (ORs) generated by multivariate logistic regression of in-hospital AEs between women and men on the basis of baseline RV parameters. Results 59 patients (median age 62 years, 42.37% male, functional tricuspid regurgitation in 62.71%) were finally enrolled. In-hospital AEs were identified in 23 patients (3 death, 5 shock, 5 renal failure, 10 prolonged mechanical ventilation). The risk of AEs was increased from baseline, when the ESV was 69.73 mL for women and 90.66 mL for men. Regarding EDV, the risk for women increased at 130.49 mL compared with 170.36 mL in men. Accordingly, when indexed by body surface area, women had a lower inflection point for both EDVi and ESVi (76.71 mL/m2 vs 91.35 mL/m2, 34.04 mL/m2 vs 52.49 mL/m2). However, there was no inflection point for increased risk with RVEF in either men or women. Conclusion Women undergoing ITVS have a higher risk of in-hospital AEs with smaller RV size. These results support the use of sex-specific thresholds for RV size when making surgical decisions in patients with severe tricuspid regurgitation.Figure 1.Adjusted ORs for RV size.