Psoas Muscle Size Predicts Risk-Adjusted Outcomes After Surgical Aortic Valve Replacement

Background Frailty is an important predictor of outcomes after cardiac surgery, but utility is limited by difficult assessment and quantification. We hypothesize that sarcopenia defined as psoas muscle cross-sectional area is a useful predictor of surgical aortic valve replacement outcomes in moderate to high-risk patients. Methods Moderate to high risk patients (predicted risk of mortality greater than 3%) who underwent surgical aortic valve replacement with or without coronary artery bypass were extracted from an institutional database (2009 to 2016). Psoas index was calculated as the cross-sectional area of the psoas muscle at the L4 vertebral level normalized to body surface area. Patients were stratified by sarcopenia status, defined as less than 25th sex-specific percentile. Multivariable regression analysis identified risk-adjusted associations with psoas index using The Society of Thoracic Surgeons predicted risk scores. Results Of the 240 patients included, the median predicted risk of mortality was 6%, median age 80 years, and 40% were female. Patients with (33.3%) and without (66.7%) sarcopenia had equivalent baseline risk (median predicted risk of mortality 5.7% versus 6.0%, p = 0.29). Patients with sarcopenia had higher 1-year mortality (31.9% versus 16.9% p = 0.03). Psoas index significantly predicted risk-adjusted 1-year mortality (odds ratio 0.84, p = 0.02) and long-term mortality (hazard ratio 0.92, p = 0.04), as well as risk-adjusted major morbidity, prolonged ventilation, length of stay, discharge to a facility, and hospital cost. Finally, psoas index measurements were highly reproducible (Pearson correlation coefficient 0.944). Conclusions Psoas index is an easily obtained and reproducible measure of frailty that predicts risk-adjusted resource utilization, morbidity, and long-term mortality. Psoas index may improve procedural selection and risk adjustment in high-risk patients with aortic valve disease.