ROLE OF SKELETAL-MUSCLE METABOLISM IN EXERCISE CAPACITY OF PATIENTS WITH MYOCARDIAL-INFARCTION STUDIED BY PHOSPHORUS-31 NUCLEAR-MAGNETIC-RESONANCE

Patients with congestive heart failure reportedly show a poor correlat ion between cardiac function and exercise tolerance. Recent studies ha ve demonstrated that skeletal muscle is the main factor that limits ex ercise tolerance. However, the relationship between high-energy phosph ate metabolism in skeletal muscle and exercise tolerance has not been well defined. Exercise capacity was assessed in 35 subjects with myoca rdial infarction in terms of peak oxygen consumption (peak VO2) during treadmill exercise with an analysis of expired gases. On the same day , changes in high-energy phosphates in finger flexor muscle during han dgrip exercise were measured by magnetic resonance spectrometry. Phosp hocreatine (PCr) utilization and the decrease in pH during handgrip ex ercise were significantly greater in patients with a poor exercise cap acity and their time constant of recovery of PCr was prolonged. The ra tios of PCr/Pi (Pi: inorganic phosphate) and PCr/HMPA (HMPA: hexamethy lphosphoramide) during exercise and the time constant of recovery of P Cr were significantly correlated with peak VO2. These results suggest that skeletal muscle metabolism governs exercise tolerance.