A neural link to explain the "muscle hypothesis" of exercise intolerance in chronic heart failure.
BACKGROUND
In chronic heart failure the cause of exercise limitation is still unclear: ergoreceptors, muscle afferents sensitive to exercise metabolites, are proposed as a neural link between muscular abnormalities and the limited exercise responses in this syndrome.


METHODS
In 92 stable patients with heart failure (34 in New York Heart Association class I, 27 in class II, and 31 in class III) and 28 age-matched normal controls, we assessed exercise tolerance (maximal upright bicycle) and ergoreflex activity (2 dynamic hand grips: one control and one followed by 3 minutes of local circulatory occlusion to isolate the ergoreflex component by metabolite trapping).


RESULTS
Patients, with respect to the controls, showed reduced exercise tolerance (peak VO2: 20 vs 33 mL/kg/min), increased ergoreflex effects on ventilation (9 vs 4 L/min), systolic pressure (37 vs 13 mm Hg), and leg vascular resistance (45 vs 22 units) (all P <.005); with the progression of the symptoms, a progressive increase in ergoreflex contribution to the ventilatory response to exercise was observed. The indexes of exercise limitation during arm and leg exercise (ie, peak VO 2, V/VCO2 slope) correlated highly with the ergoreflex contribution to ventilatory response during handgrip test ( r </= 0.7, P <.0001) but weakly with left ventricular ejection fraction (r </= 0.5).


CONCLUSIONS
In chronic heart failure, the overactivity of the ergoreflex is related to a degree of functional limitation and appears, through direct ventilatory and cardiovascular responses, to contribute to the abnormal responses to exercise, explaining the "muscle hypothesis."
Piepoli
M
M
Department of Cardiac Medicine, Royal Brompton Hospital, London, UK. piepolim@tin.it
Ponikowski
P
P
Clark
A L
AL
Banasiak
W
W
Capucci
A
A
Coats
A J
AJ
D000368:Aged; D000704:Analysis of Variance; D002908:Chronic Disease; D005080:Exercise Test / Q000379:methods / Q000706:statistics & numerical data; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000145:classification / Q000503:physiopathology*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation* / Q000503:physiopathology; D012018:Reflex / Q000502:physiology; D012044:Regression Analysis; D012119:Respiration; D011984:Sensory Receptor Cells / Q000503:physiopathology*