Six-month trajectory of phase angle after cardiovascular surgery and associated factors of the recovery during cardiac rehabilitation: A retrospective cohort study

Abstract

Background and aims: Although the phase angle (PhA), a measure of frailty and sarcopenia, determined by bioelectrical impedance analysis has been reported as a prognostic factor after cardiovascular surgery, few studies have reported the trajectory of the PhA after discharge. In this study, we examined the trajectory of the PhA along with conventional physical function measures and explored the factors associated with recovery for 6 months after hospital discharge in patients who had undergone cardiovascular surgery.

Methods: We included 116 patients who underwent elective cardiovascular surgery and cardiac rehabilitation after discharge. The PhA, physical function measures (grip strength, knee extension isometric muscle strength [KEIS], and usual gait speed), and Geriatric Nutritional Risk Index (GNRI) were assessed preoperatively, at discharge, and 3 and 6 months. Correlations between the PhA recovery rates and physical function and nutritional indices were assessed using Spearman's correlation analysis. Multivariate linear regression analysis was performed to examine the factors associated with recoveries of PhA and physical function indices (grip strength, KEIS, gait speed) after discharge.

Results: Mean values of the PhA and physical function measurements and the GNRI score at discharge were lower than the preoperative values (PhA, -8.0 %; grip strength, -8.7 %; KEIS, -6.9 %; usual gait speed, -8.3 %; GNRI, -11 %). The grip strength, KEIS, and gait speed recovered to almost preoperative values 3 months after discharge. Values for the PhA and GNRI were still lower than preoperative values 3 months after discharge but had recovered to preoperative values at 6 months. The PhA was not significantly correlated with the recovery rates of the other indicators. Older age was negatively associated with PhA recovery rate, however, recovery rates decreased significantly with post-discharge physical activity.

Conclusions: In patients undergoing cardiovascular surgery, the PhA takes longer to recover than muscle strength or gait speed, requiring up to 6 months to recover to preoperative levels. Post-discharge interventions to increase daily physical activity may be an important method of speeding PhA recovery.

Keywords: Cardiac rehabilitation; Cardiovascular surgery; Nutritional indicator; Phase angle; Physical function; Trajectory.