Skeletal muscle endurance and muscle metabolism in patients with chronic heart failure.
BACKGROUND
Alterations in skeletal muscle function are known to contribute to exercise intolerance in patients with chronic heart failure (CHF).


OBJECTIVE
To evaluate whether muscle isometric endurance can be objectively measured and whether it is related to skeletal muscle metabolism in CHF.


METHODS
Isometric endurance of the vastus lateralis, measured as time to fatigue (T(F)), was evaluated in 25 patients with CHF (55+/-8 years of age [mean +/- SD]) and 18 healthy subjects (HS) (62+/-6 years of age [mean +/- SD]). Median frequency of surface electromyography was obtained from spectral analysis using a fast Fourier transformation. Citrate synthase (CS), 3-hydroxyacyl-CoA dehydrogenase (HADH), hexokinase (HK) and phosphofructokinase (PFK) activities were determined from the right vastus lateralis muscle.


RESULTS
T(F) was lower in CHF patients than in HS (49+/-4 s and 80+/-7 s, respectively; P<0.01). Muscle fatigue was present at the end of the endurance test in both groups (median frequency breakpoint at mid-exercise for both groups [P<0.05]). CS (P<0.01) and HK (P<0.01) activities were lower in CHF patients than in HS, but PFK activity was higher (P<0.05). T(F) correlated significantly with CS (r=0.50), HADH (r=0.42), PFK (r=-0.47) and HK (r=0.41) activities and the PFK/CS ratio (r=-0.39) when both groups were considered, and with HADH (r=0.47) and PFK (r=-0.57) activities for the CHF group alone (all P<0.05).


CONCLUSIONS
These results suggest that isometric endurance of the vastus lateralis muscle is reduced in patients with CHF and that it is related to a reduced muscle oxidative capacity.
Brassard
Patrice
P
Centre de recherche, Hôpital Laval, Institut universitaire de cardiologie et de pneumologie, Université Laval, Ste-Foy, Québec, Canada.
Maltais
Francois
F
Noel
Martin
M
Doyon
Jean-François
JF
LeBlanc
Pierre
P
Allaire
Joakim
J
Simard
Clermont
C
Leblanc
Marie-Hélène
MH
Poirier
Paul
P
Jobin
Jean
J
D049628:Body Size / Q000502:physiology; D015444:Exercise / Q000502:physiology; D005260:Female; D006333:Heart Failure / Q000378:metabolism* / Q000503:physiopathology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology*; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology