Association between preoperative phase angle and all‐cause mortality after cardiovascular surgery: A retrospective cohort study

Background The importance of preoperative physical function assessment for post‐operative intervention has been reported in older patients undergoing cardiovascular surgery. Phase angle (PhA), measured using bioelectrical impedance analysis, is an indicator of cellular health and integrity and is reported as a prognostic factor in several chronic diseases; however, its association with the long‐term prognosis of cardiovascular surgery remains unclear. This study aimed to investigate the prognostic value of PhA for long‐term mortality in patients undergoing cardiovascular surgery. Methods This retrospective cohort study included consecutive patients who underwent elective cardiovascular surgery between October 2016 and March 2021 at Nagoya Heart Center, Japan. PhA was assessed using bioelectrical impedance analysis before surgery, and physical function measures (gait speed, grip strength and short physical performance battery [SPPB]) were measured synchronously. The association between PhA and all‐cause mortality after discharge was assessed using Kaplan–Meier and multivariate Cox regression analyses. The incremental prognostic value of PhA was compared with other physical function measures using net reclassification improvement (NRI) and integrated discrimination improvement (IDI). Results A total of 858 patients were included in the present analysis (mean age = 68.4 ± 11.9 years, 67.6% male). PhA positively correlated with body mass index (ρ = 0.38, P