Reduced exercise tolerance in CHF may be related to factors other than impaired skeletal muscle oxidative capacity

We sought to determine whether skeletal muscle oxidative capacity, fiber type proportions and fiber size, capillary density or muscle mass might explain the impaired exercise tolerance in chronic heart failure (CHF). Previous studies are equivocal regarding the maladaptations that occur in the skeletal muscle of patients with CHF and their role in the observed exercise intolerance. Total body O2 uptake (peak) was determined in 14 CHF patients and 8 healthy sedentary similarly-aged controls. Muscle samples were analysed for mitochondrial ATP production rate (MAPR), oxidative and glycolytic enzyme activity, fiber size and type, and capillary density. CHF patients demonstrated a lower peak (15.1 ± 1.1 vs. 28.1 ± 2.3 ml.kg&VO2&VO2-1.min-1, p<0.001) and capillary to fiber ratio (1.09 ± 0.05 vs. 1.40 ± 0.04; p