SKELETAL-MUSCLE METABOLISM DURING EXERCISE IN PATIENTS WITH CHRONIC HEART-FAILURE

Objective-To investigate the metabolic response of skeletal muscle to exercise in patients with chronic heart failure and determine its rela tion to central haemodynamic variables. Setting-University hospital in Sweden. Participants-16 patients in New York Heart Association class II-III and 10 healthy controls. Main outcome measures-Skeletal muscle biopsies were obtained from the quadriceps muscle at rest and at subma ximal and maximal exercise. Right sided heart catheterisation was perf ormed in eight patients. Results-The patients had lower maximal oxygen consumption than the control group (13.2 (2.9) v 26.8 (4.4) ml/kg/min , P < 0.001). They had reduced activities of citrate synthetase (P < 0 .05) and 3-hydroxyacyl-CoA dehydrogenase (P < 0.05) compared with the controls. At maximal exercise adenosine triphosphate (P < 0.05), creat ine phosphate (P < 0.01), and glycogen (P < 0.01) were higher whereas glucose (P < 0.001) and lactate (P < 0.06) were lower in the patients than in the controls. Citrate synthetase correlated inversely with ske letal muscle lactate at submaximal exercise (r = -0.90, P < 0.003). No correlations between haemodynamic variables and skeletal muscle glyco gen, glycolytic intermediates, and adenosine nucleotides during exerci se were found. Conclusion-Neither skeletal muscle energy compounds nor lactate accumulation were limiting factors for exercise capacity in p atients with chronic heart failure. The decreased activity of oxidativ e enzymes may have contributed to the earlier onset of anaerobic metab olism, but haemodynamic variables seemed to be of lesser importance fo r skeletal muscle metabolism during exercise.