Contribution of Muscle Afferents to the Hemodynamic, Autonomic, and Ventilatory Responses to Exercise in Patients With Chronic Heart Failure: Effects of Physical Training

Abstract

Background A neural linkage between peripheral abnormalities and the exaggerated exercise responses in chronic heart failure (CHF) was postulated. We studied the ergoreceptors (afferents sensitive to skeletal muscle work) in CHF and whether training can affect their activity. Methods and Results In 12 stable CHF patients (ejection fraction [EF]=26.4%) and 10 control subjects (EF=55.3%), we compared the responses to dynamic handgrip and during a 3-minute period of posthandgrip regional circulatory occlusion (PH-RCO). The ergoreflex contribution was quantified as the percentage responses to exercise maintained by PH-RCO compared with recovery without PH-RCO. Patients showed ergoreflex overactivation compared with control subjects in terms of ventilation (86.5% versus 54.5%), diastolic pressure (97.8% versus 53.5%), and leg vascular resistance (108.1% versus 48.9%) (all P <.05). The contribution of the ergoreflex to vagal withdrawal (high frequency of RR variability) and sympathetic activation (low frequency of RR, pressure variability) was evident in both groups. Nine control subjects and nine CHF patients participated in 6 weeks of forearm training. Training reduced the ergoreflex contributions more in CHF than in control subjects: diastolic pressure (−33.2% versus −4.6%), ventilation (−57.6% versus −24.6%), and leg vascular resistance (−59.9% versus −8.0%) (all P <.05). Conclusions (1) The ergoreflex role has a larger effect on the responses to exercise in CHF than in control subjects. (2) Training may reduce this exaggerated ergoreflex activity, thereby improving the responses to exercise.