Evaluation of energy metabolism in skeletal muscle of patients with heart failure with gated phosphorus-31 nuclear magnetic resonance.

Exertional fatigue is a major limiting symptom in patients with heart failure. To investigate the metabolic basis of this fatigue, we used gated nuclear magnetic resonance spectroscopy to compare inorganic phosphate (Pi), phosphocreatine (PCr) and pH levels, and fatigue (1 to 4+) during mild forearm exercise in eight normal men and nine men with heart failure. Wrist flexion every 5 sec for 7 min was performed at 1, 2, and 3 J (average power output = 0.2, 0.4, and 0.6 W). In both groups linear relationships were noted between power output and Pi/PCr; the slope of this relationship was used to compare PCr depletion patterns. At rest both groups had similar Pi/PCr ratios (normal subjects 0.12 +/- 0.06, those with heart failure 0.15 +/- 0.03) and pH (normal subjects 7.04 +/- 0.13, those with heart failure 7.10 +/- 0.11). In normal subjects exercise resulted in a progressive increase in Pi/PCr (slope = 1.17 +/- 0.20 Pi/PCr units/W), a reduction in pH only at 0.6 W (0.2 W: 7.03 +/- 0.10, 0.4 W: 7.01 +/- 0.10, 0.6 W: 6.88 +/- 16) and moderate fatigue (0.2 W: 0 +/- 0, 0.4 W: 1.3 +/- 0.5, 0.6 W: 1.9 +/- 0.6). In patients with heart failure exercise resulted in significantly greater fatigue at all workloads (0.2 W: 1.0 +/- 0.5, 0.4 W: 1.9 +/- 0.6, 0.6 W: 2.9 +/- 0.5).(ABSTRACT TRUNCATED AT 250 WORDS)