SKELETAL-MUSCLE FUNCTION AT LOW WORK LEVEL AS A MODEL FOR DAILY ACTIVITIES IN PATIENTS WITH CHRONIC HEART-FAILURE

Aim Metabolic exercise abnormalities have been reported in chronic hea rt failure patients. This study sought to evaluate whether these abnor malities affected daily activity. Methods and results In 16 patients w ith moderate-to-severe chronic heart failure and in eight controls we measured femoral flow (thermodilution) and metabolism (glucose, lactat e, free fatty acids, blood gas values) at rest and during a constant l oad of 20 W, which may mimic a daily activity. At rest, chronic heart failure patients had a leg flow similar to controls, but showed a high er leg oxygen consumption (4.6 +/- 0.6 vs 2.6 +/- 0.4 ml.min(-1); P<0. 05), a higher arteriovenous oxygen difference (7.2 +/- 0.5 vs 5.4 +/- 0.7 ml.dl(-1): P<0.05), and a lower femoral vein pH (7.37 +/- 5.-03 vs 7.42 +/- 0.01: P=0.01). At 20 W, chronic heart failure patients had a leg flow similar to controls, but showed increased lactate release (f rom resting 11.7 +/- 33 to 142 +/- 125 mu g.min(-1) P<0.0001 vs contro ls, from resting 5.7 +/- 15.4 to 50 +/- 149 mu g.min(-1) ns), higher a rterial concentration of free fatty acids (781 +/- 69 vs 481 +/- 85 mu mol.1(-1): P<0.01), lower femoral vein HCO3 (24.1 +/- 2.6 vs 26.3 +/- 1.7 mmol.1(-1); P<0.05) and base excess (-2.3 +/- 2.3 vs -0.24 +/- 1. 7 mmol.1(-1); P=0.01). Conclusion In chronic heart failure patients, t he important cellular metabolic alterations already present at rest pa rtially affect daily activities, owing to a further decrease in the ef ficiency of muscle metabolic processes, and may preclude tolerance of heavier activities. Such alterations appear, at least in part, indepen dent of peripheral haemodynamic responses to exercise.