The revised cardiac risk index and 90-day mortality after non-cardiac surgery: a retrospective cohort study

Background The Revised Cardiac Risk Index (RCRI) is widely used for predicting major cardiac complications after non-cardiac surgery, but its association with 90-day all-cause mortality is less well established. This study aimed to evaluate the independent association between RCRI scores and 90-day all-cause mortality in a large, diverse cohort of patients undergoing non-cardiac surgery. Methods We conducted a retrospective cohort study using data from 54,933 adult patients who underwent non-cardiac surgery at a tertiary care center in Singapore between 2012 and 2016. RCRI scores were calculated based on six clinical variables and categorized into four classes. The primary outcome was 90-day all-cause mortality. Survival analysis was performed using Kaplan–Meier curves and multivariable Cox proportional hazards models, with adjustments for demographic and clinical covariates. Results A total of 735 patients (1.3%) died within 90 days postoperatively. Kaplan–Meier analysis revealed significantly poorer survival in higher RCRI classes (log-rank p < 0.001). In the fully adjusted model, compared to RCRI Class I, the hazard ratios for 90-day mortality were 1.97 (95% CI: 1.54–2.52) for Class II, 1.93 (95% CI: 1.45–2.58) for Class III, and 3.08 (95% CI: 2.29–4.15) for Class IV ( p for trend <0.001). Subgroup analyses confirmed consistent associations across age, sex, ASA class, and surgical priority groups. Conclusion Higher RCRI scores are independently associated with increased 90-day mortality after non-cardiac surgery, demonstrating a clear dose–response relationship. These findings support the use of RCRI as a practical and effective tool for preoperative risk stratification in diverse surgical populations.