Muscle high-energy metabolites and metabolic capacity in patients with heart failure

Background: Various abnormalities in skeletal muscle have been demonstrated by biopsy in patients with chronic heart failure (CHF). In mammalian muscles. high-energy metabolite composition at rest (HEMC) provides data on important metabolic characteristics: however, the significance of HEMC has not been clarified in patients with CHF. Therefore, we investigated HEMC in normal subjects and patients with CHF and examined its relation to muscle metabolic capacity and exercise tolerance. Methods: High-energy metabolites (phosphocreatine (PCr), inorganic phosphate (Pi), and ATP) in resting calf muscle were measured by P-31-magnetic resonance spectroscopy (P-31-MRS), and ratios of Pi to PCr. Pi to ATP, and PCr to ATP were calculated in 34 patients with CHF and 13 age- and size-matched normal subjects. Muscle metabolism was evaluated during local exercise of unilateral plantar flexion by P-31-MRS. Metabolic capacity was estimated by the rate of PCr breakdown in relation to the workload. Systemic exercise capacity was evaluated by a bicycle ergometer. Results: The ratio of PCr to ATP was significantly increased in patients with CHF compared with controls (3.06 +/- 0.43 vs 2.72 +/- 0.36, P < 0.05) and was significantly correlated with metabolic capacity (r = -0.37. P < 0.01) and with peak oxygen uptake (r = -0.45, P < 0.01). There was a significant correlation between metabolic capacity and peak oxygen uptake (r = 0.53, P < 0.001). Conclusion: HEMC was altered in patients with CHF, and this change was related to metabolic capacity and exercise capacity. These findings provide new insight into the mechanism of impaired muscle metabolism in CHF.