Abstract
Background It has been suspected for some time that patients with chronic heart failure (CHF) have abnormal muscle metabolism, so in the present study the muscle metabolism of the arm and leg were compared by 31P magnetic resonance spectroscopy (31P-MRS) to examine the relationship to exercise tolerance. Methods and Results The study group comprised 13 patients and 11 normal controls. Calf-plantar and forearm-wrist flexion were performed to evaluate the metabolic capacity assessed as the phosphocreatine breakdown rate (PCr-slope) and muscle pH at a submaximal (70% peak) work rate (submax-pH). Exercise of both the arm and leg resulted in an earlier decrease in PCr and muscle pH in patients with CHF compared with controls. There were significant correlations between peak oxygen uptake (peak VO2) and the PCr-slope in both limbs in patients with CHF (forearm: r=0.63, p<0.05; calf: r=0.60, p<0.05), but no correlations in normal controls. There was a close correlation between the ventilatory anaerobic threshold (AT) and the PCr-slope in the calf (r=0.85, p<0.01), but not in the forearm in patients with CHF. Submax-pH in both upper and lower limbs was not significantly correlated to peak VO2 or AT in either patients with CHF or controls. Conclusions Although metabolic abnormalities during exercise are seen in both arms and legs, leg muscle abnormalities, in particular, are closely related to systemic exercise intolerance in patients with CHF. (Circ J 2004; 68: 573 - 579)
