Skeletal muscle quality, measured via phase angle, and cardiorespiratory fitness in patients with obesity and heart failure with preserved ejection fraction

Objectives: Cardiorespiratory fitness (CRF) is influenced by body composition quantity and quality in heart failure with preserved ejection fraction (HFpEF) and obesity. Bioelectrical impedance analysis (BIA) provides a noninvasive quantitative and qualitative body composition assessment. The aim of this study was to determine the role of phase angle (PhA), a BIA-measure of skeletal muscle quality and body cell mass, on CRF in patients with obesity and HFpEF.

Methods: Fifty-nine consecutive outpatients with HFpEF underwent cardiopulmonary exercise testing to measure CRF. Single-frequency segmental BIA was used to measure PhA and body composition quantity. Resting Doppler echocardiography and biomarkers were measured to assess cardiac function and systemic inflammation.

Results: Compared with patients with lower PhA, patients with higher PhA (above mean 5.8°) presented a greater absolute peak oxygen consumption (VO₂; 1.83 [1.3-2.1] versus 1.39 [1.1-1.6] L/min, P = 0.003), VO_{2 peak} adjusted for body weight (17.5 [12.3-18.1] versus 13.3 [12.7-15.2] mL/kg/min, P = 0.040), and a lower edema index (48.7 [2.9] versus 51.4% [2.7], P < 0.001) and N-terminal pro-B-type natriuretic peptide (NT-proBNP; 64 [50-121] versus 183 [68-343.5] pg/dL, P < 0.001). In the overall sample, PhA was correlated with absolute VO_{2 peak} (r = 0.468, P < 0.001), VO_{2 peak} adjusted for body weight (r = 0.368, P = 0.004), VO_{2 peak} adjusted for fat-free mass (r = 0.315, P = 0.015), edema index (r = -0.508, P < 0.001), and NT-proBNP (r = -0.579, P < 0.001). PhA remained a significant predictor for CRF even after adjustment for potential confounders and HFpEF severity.

Conclusion: In patients with obesity and HFpEF, a greater PhA is an independent predictor for favorable CRF.