Prognostic Value of Psoas Muscle Mass Index in Patients With Non‒ST‐Segment‒Elevation Myocardial Infarction: A Prospective Observational Study

BACKGROUND: Muscle wasting is an important predictor of long‐term outcome in patients with cardiovascular disease, but the prognostic value of muscle wasting in patients with non‒ST‐segment‒elevation myocardial infarction is not established. The aim of this study is to investigate the prognostic value of muscle wasting, defined by psoas muscle mass index (PMI), in patients with non‒ST‐segment‒elevation myocardial infarction. METHODS AND RESULTS: A total of 132 consecutive patients with non‒ST‐segment‒elevation myocardial infarction were prospectively enrolled between 2015 and 2018. Primary end point was incidence of cardiovascular events including cardiovascular deaths, non‐fatal myocardial infarction, or non‐fatal stroke. Cross‐sectional area of the psoas muscle at the L3 vertebral level was obtained by computed tomography and PMI was calculated. The median follow‐up period was 2.4 years (interquartile range, 1.1–4.0 years). There were 45 cardiovascular events (34%) during the study periods. The optimal cutoff value of PMI to predict cardiovascular events was 772 mm(2)/m(2), as assessed by receiver operating curve analysis. Patients with reduced PMI (PMI<772 mm(2)/m(2)) had significantly higher cardiovascular events than those with preserved PMI (PMI≥772 mm(2)/m(2)) (48% versus 21%; log‐rank test P<0.001). Multivariate Cox proportional hazards model revealed that reduced PMI was a statistically significant predictor of cardiovascular events (hazard ratio, 3.30; 95% CI, 1.70–6.40; P<0.001). CONCLUSIONS: Muscle wasting defined as PMI is a simple and useful objective marker to predict future cardiovascular outcome in patients with non‒ST‐segment‒elevation myocardial infarction. REGISTRATION INFORMATION: URL: https://www.umin.ac.jp/ctr/; Unique identifier: UMIN000013445.