Resting metabolism energy expenditure as a surrogate of muscle mass quantification in patients with heart failure and reduced ejection fraction: a pilot prospective cohort study

Abstract Introduction Sarcopenia is associated with poorer prognosis in heart failure patients. However, measuring muscle mass in clinical practice remains challenging. Given the significant role of muscle mass in energy expenditure among healthy individuals, we hypothesized that resting energy expenditure (REE) could serve as a surrogate for muscle mass quantification in patients with heart failure and reduced ejection fraction (HFrEF), a hypothesis not previously tested. Objective To evaluate the relationship between REE and muscle mass quantification in HFrEF patients. Methods In this prospective cohort study, we recruited consecutive patients with HFrEF. Participants underwent dual-energy X-ray absorptiometry (DEXA) and a 30-minute resting metabolism test (RMT) at the same day. Muscle mass was quantified using DEXA, by subtracting bone mineral composition from the obtained whole-body lean mass and adjusted for body surface area. REE was estimated via indirect calorimetry based on the most stable 10-minute period over a 30-minute assessment. Statistical analysis was conducted using Pearson correlation and linear regression to assess the strength and direction of the relationship between these variables and determine the extent to which REE could predict muscle mass quantification. Results We recruited 24 patients (79% male, mean age 66; mean LVEF 38±7%). This cohort included patients with ischemic heart disease (n=14), dilated cardiomyopathy (n=5), valvular heart disease (n=4) and burnout hypertrophic cardiomyopathy (n=1). The mean muscle mass adjusted for body surface area was 23.4±2.5 kg/m2, and the mean REE was 1.56±0.35 kcal/min. Notably, there was a considerable disparity in the relationship between muscle mass and REE, with muscle mass ranging from 18.9 to 28.9 kg/m² and REE ranging from 1.07 to 2.23 kcal/min. A significant correlation was observed between REE and muscle mass (Pearson coefficient 0.752, p0.001). Linear regression demonstrated a strong relationship between these two variables (Muscle mass = 14.67 + 5.7*REE; R² = 0.57) – Figure 1. Conclusion Resting energy expenditure showed a significant correlation with muscle mass quantification in patients with HFrEF, suggesting it could serve as a viable surrogate. Given the promising results of this pilot study, further validation of these findings in real-world settings is warranted. The next phase of this study will involve integrating a simplified resting metabolism protocol during the resting phase of cardiopulmonary exercise testing (CPET) to assess its applicability in a routine clinical practice scenario.