The psoas muscle index as a predictor of long-term survival after cardiac surgery for hemodialysis-dependent patients

Sarcopenia represented by skeletal muscle depletion is closely related to frailty and predicts prognoses in the general population. However, its predictive value for hemodialysis (HD)-dependent patients undergoing cardiac surgery has not been fully investigated. We aimed to clarify the impact of sarcopenia on the outcomes of HD-dependent patients after cardiac surgery. We retrospectively reviewed 138 HD-dependent patients who underwent cardiac surgery between January 2006 and December 2017. Sarcopenia was assessed using the psoas muscle index (PMI), which was calculated using values measured on preoperative computed tomography images and the following formula: cross-sectional area of bilateral psoas muscle/height(2). Patients were divided into two groups according to the PMI: the sarcopenia group (<= 443 mm(2)/m(2) for men and <= 326 mm(2)/m(2) for women; n = 35) and the non-sarcopenia group (> 443 mm(2)/m(2) for men and > 326 mm(2)/m(2) for women; n = 103). Preoperative characteristics and surgical outcomes were compared. Overall in-hospital mortality did not differ between the sarcopenia and non-sarcopenia groups. However, the patients with sarcopenia had significantly decreased long-term survival. Multivariate analysis revealed that low PMI was a significant independent predictor of long-term mortality (hazard ratio, 1.92; 95% confidential interval, 1.19-3.17; p < 0.01). Long-term survival rates in HD-dependent patients undergoing cardiac surgery are severely affected by the presence of preoperative sarcopenia defined by PMI. Preoperative risk analysis using the PMI might contribute to risk stratification of and decision-making for HD-dependent patients undergoing cardiac surgery.