[A study of forearm muscle metabolism in patients with chronic heart disease]

To assess forearm exercise capacity and exercise energy metabolism in relationship to forearm muscle mass and blood flow in patients with chronic heart disease, 22 patients (NYHA class I (C1) 8, class II(C2) 10, class III (C3) 4) and 10 normal subjects were studied using Phosphorus-31 magnetic resonance spectroscopy (31P-MRS). First, the maximal cross sectional area (MCA) of the forearm flexor muscles was estimated in each individual using magnetic resonance imaging. Then, during multistage forearm flexor exercise, 31P-MRS was performed to estimate phosphocreatine (PCr), inorganic P (Pi), and intracellular pH. Forearm blood flow was measured by plethysmography. An initial work load of forearm exercise was decided by MCA as 1 J/cm2, and multistage exercise was done with an increment of 1 J/min/cm2 to the point of maximal muscle exhaustion. The maximal load (J/min) was decreased in cardiac groups as NYHA class advanced. However, the difference among all groups except group C3 was not significant when the max load was adjusted for muscle MCA. As the work load was increased during forearm exercise, PCr and intracellular pH decreased, and Pi increased in every group. Standardized PCr [PCr/(PCr + Pi)] was lower in group C2 and C3 than in group N at each work load. At high work loads, intracellular pH tended to be lower in group C2 and C3 than in group N and C1. Forearm blood flow during forearm exercise was not different among the four groups. In the maximal exercise test using upright ergometer, peak oxygen uptake and anaerobic threshold were lower in group C1, C2 and C3 than in group N.(ABSTRACT TRUNCATED AT 250 WORDS)