Skeletal muscle metabolism at rest and exercise in patients with severe but compensated left ventricular dysfunction: A ³¹P nuclear magnetic resonance study

Abnormalities of high-energy phosphate metabolism in skeletal muscle have been described in patients with heart failure. We examined 8 patients with a past history of symptomatic heart failure, all New York Heart Association class III, who had improved two classes following long-term therapy with digoxin, furosemide, and converting enzyme inhibitors. Skeletal muscle ³¹P nuclear magnetic resonance spectroscopy was performed in this group of patients, with a mean left ventricular ejection fraction of 15 ± 7% after therapy, and compared to 8 normal control subjects. Magnetic resonance spectra were recorded from the flexor digitorum superficialis during rest, exercise, and recovery, employing previously described protocols. Relative tissue concentrations of phosphocreatine and inorganic phosphate and tissue pH were determined. The phosphocreatine fraction [(PCr)/{(PCr)+(Pi)}] was taken as an index of high-energy phosphate consumption and synthesis. The end-exercise pH was 6.55 ± 0.22 for the heart failure group and 6.60 ± 0.18 for controls. The phosphocreatine fraction was 0.42 ± 0.19 and 0.43 ± 0.11 immediately at the end of exercise and 0.81 ± 0.12 and 0.80 ± 0.08 8 min thereafter for heart failure patients and controls, respectively. No statistically significant differences were found for pH or phosphocreatine fraction at any time between the patient and control groups. We conclude that heart failure patients who demonstrate a beneficial symptomatic response to therapy with continuing severe left ventricular dysfunction do not manifest previously reported abnormalities of skeletal muscle high-energy phosphate metabolism.