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.