Is there a relationship between muscle fatigue resistance and cardiovascular responses to isometric exercise in mild chronic heart failure?

Background: Exercise intolerance in chronic heart failure (CHF) may be due to altered fatigue resistance and muscle afferent input to the cardiovascul ar system from dysfunctional skeletal muscle. Aim: To determine whether cal f muscle fatigue resistance was associated with the magnitude of a muscle a fferent driven cardiovascular response to isometric exercise. Methods ann r esults: Cardiovascular responses were recorded in eight stable CHF patients (ejection fraction 20-40%) and nine healthy, age-matched controls during v oluntary and electrically evoked isometric plantar flexion and post-exercis e circulatory occlusion. The force developed by the plantar flexors during a 2-min submaximal electrically evoked fatigue test was measured. There was no relationship between ischaemic muscle fatigue and cardiovascular change s during and after voluntary contraction in either group nor evoked contrac tion in the CHF group. In the control group, the change in diastolic blood pressure (DBP) at the end of evoked contraction was related to the severity of fatigue at 90 s and 120 s (FI = 0.01 Delta DBP + 0.3, r = 0.81, P < 0.0 5 and FI = 0.02<Delta>DBP + 0.8, r = 0.84, P < 0.01, respectively). Conclus ion: Muscle fatigue resistance did not relate to the magnitude of the cardi ovascular stress generated by isometric exercise of the same muscle in thes e patients. (C) 2001 European Society of Cardiology. All rights reserved.