Abstract 18484: Impaired Skeletal Muscle Efficiency and Power After Correction for Lean Muscle Mass in Patients With Advanced Heart Failure

Abstract

Introduction: Patients with advanced heart failure (HF) develop metabolic abnormalities leading to skeletal muscle wasting and changes in body composition that include lean skeletal muscle and adipose tissue. Hypothesis: We hypothesized that HF subjects have decreased skeletal muscle efficiency, work performance and muscle power compared to control subjects. Methods: Whole body dual-energy X-ray absorptiometry (DEXA) scanning for determination of total body mass, fat mass, % body fat, lean body mass was performed in 9 control subjects (age 51±8 yrs, EF 63.0±4.2 %, BMI 25.7±28.2 kg/m 2 , peak VO2 30.3±7.4 mL/kg/min) and 31 HF subjects (age 59±10 yrs, EF 27.9±7.8 %, BMI 28.2±4.7 kg/m 2 , peak VO2 15.3±3.8 mL/kg/min). Muscle function was assessed by isometric and isokinetic functional testing using the Biodex System 4 Pro of all extremities. Functional parameters were corrected for lean muscle mass determined by DEXA scanning. Results: Total fat mass and percentage body fat were higher in HF subjects (fat mass: 25.5±7.8 vs 16.4±4.8 kg in controls; p=0.002; % body fat: 31±7 vs 23±7 % in controls; p=0.006) without differences in any of the parameters of lean muscle mass. After correction for lean muscle mass, HF subjects showed decreased muscle power (0.32±0.15 vs 0.45±0.13 watts/kg in controls; p=0.02) and total muscle work (2.57±1.16 vs 3.58±0.94 J/kg in controls; p=0.02) in the lower extremities. Of note, no differences between HF and control subjects were found in the upper extremities. Conclusion: HF subjects have similar lean muscle mass compared to controls. Skeletal muscle power and work performance is significantly reduced in HF subjects even when normalized for lean muscle mass. These novel findings indicate the development of an intrinsic skeletal myopathy that is impairing muscle performance and likely contributes to increased fatigue and frailty in patients with advanced HF.