Skeletal muscle index determined by bioelectrical impedance analysis is a determinant of exercise capacity and a prognostic predictor in patients with congenital heart disease

Abstract

Background: Patients with congenital heart disease (CHD) reportedly have reduced exercise capacity. Underlying cardiac anatomy and a sedentary lifestyle are thought to be associated with exercise impairment. However, little has been reported regarding the relationship between quantitative body composition and exercise capacity. Bioelectrical impedance analysis (BIA) is a rapid and safe assessment method that has been widely used in clinical research. We hypothesized that bioelectrical impedance parameters are determinants of exercise capacity, and the skeletal muscle index (SMI) determined by BIA is a prognostic predictor in patients with CHD.

Methods: We conducted a retrospective single-center study of 305 consecutive patients with CHD [median age, 26 years (range 12-60]; 48% males] admitted between 2014 and 2017. The BIA parameters were reviewed, including the edema index (EI, extracellular water to total body water ratio), SMI (skeletal muscle mass/height²), mineral index (MI, mineral mass/height²), percent body fat (%BF), and exercise capacity [peak oxygen uptake (peakVO₂)] via a cardiopulmonary exercise test.

Results: The multivariate analysis revealed a significant correlation between peakVO₂ and EI (r=0.55) and peakVO₂ and SMI (r=0.49). The receiver operating characteristic curve analysis showed that the EI cut-off for peakVO₂<20ml/kg/min was 0.386 [area under the curve (AUC), 0.77; sensitivity, 0.67; specificity 0.76], and the SMI cut-off was 7.6kg/m² (AUC, 0.78; sensitivity, 0.76; specificity 0.75). Compared with patients who had biventricular morphology, patients with single ventricular morphology had a higher EI (mean, 0.381 vs. 0.387, respectively) and lower SMI (8.5 vs. 7.7, respectively), resulting in a lower peakVO₂ (27.1 vs. 20.8, respectively). The Kaplan-Meier analysis showed that a low SMI was associated with an increased risk of future heart failure-related admissions.

Conclusions: SMI determined by BIA is a determinant of exercise capacity and can be used as a prognostic predictor in patients with CHD.

Keywords: Bioelectrical impedance analysis; Congenital heart disease; Exercise capacity; Skeletal muscle.