Association of Sarcopenia, as Defined Based on the Skeletal Muscle Index, With Mortality and Morbidity After Cardiac Surgery: A Retrospective Cohort Study

Objective: To investigate whether "sarcopenia," defined based on the preoperative skeletal muscle index (SMI), can predict major postoperative morbidity and all-cause mortality. Design: A retrospective observational cohort study. Setting: At the authors' Department of Critical Care Medicine. Participants: A total of 986 adult Chinese patients underwent cardiac surgery (coronary artery bypass graft, valve surgery, combined surgery, or aortic surgery) between January 2019 and August 2022. Measurements and main results: The skeletal muscle area at the third lumbar level (L3) was measured via preoperative computed tomography (up to 3 months from the date of imaging to the date of surgery) and normalized to patient height (skeletal muscle index). Sarcopenia was determined based on the skeletal muscle index being in the lowest sex-specific quartile. The primary outcome was all-cause mortality. The secondary outcome was major morbidity. A total of 968 patients were followed for a median of 2.00 years, ranging from 1.06 to 2.90 years. After the follow-up, 76 patients died during the follow-up period. Multivariate Cox proportional analysis showed a relationship between sarcopenia (adjusted hazard ratio 1.80, 95% CI 1.04-3.11; p = 0.034) and all-cause mortality. Kaplan-Meier curves revealed a significantly lower survival rate in the sarcopenia group than in the nonsarcopenia group. Overall, 199 (20.6%) patients had major morbidity. Multivariate analysis showed a significant relationship between sarcopenia (adjusted odds ratio = 2.21, 95% CI 1.52 similar to 3.22, p < 0.001) and major morbidity. Conclusions: Sarcopenia, defined by the skeletal muscle index, is associated with all-cause mortality and major morbidity after cardiac surgery, thereby suggesting the need for perioperative sarcopenia risk assessment for patients undergoing cardiac surgery to guide the prevention and management of adverse outcomes.