Muscle afferent and central command contributions to the cardiovascular response to isometric exercise of postural muscle in patients with mild chronic heart failure

The roles of muscle afferent activity and central drive in controlling the compromised cardiovascular system of patients with mild chronic heart failu re (CHF) during isometric exercise were examined. Blood pressure and heart rate responses were recorded in eight stable CHF patients (ejection fractio n 20-40%; age 62 +/- 11 years) and in nine healthy age-marched controls dur ing voluntary and electrically evoked isometric plantar flexion and subsequ ent postexercise circulatory occlusion (PECO). During voluntary contraction , control subjects had a greater mean increase in systolic blood pressure t han patients (42.4 +/- 19.2 and 23.0 +/- 10.9 mmHg respectively; P < 0.01), but this was not the case during PECO. During electrically evoked contract ion, but not during PECO, the CHF group had smaller (P < 0.05) mean increas es in both systolic and diastolic blood pressure than controls (13.0 +/- 5. 3 compared with 25.4 +/- 14.0 mmHg and 7.6 +/- 3.0 compared with 12.9 +/-7. 2 mmHg respectively). Intra-group comparison between responses to voluntary and electrically evoked contractions revealed greater (P ( 0.05) mean incr eases in systolic and diastolic blood pressure during the voluntary contrac tion in both the patients and the control subjects. These data suggest that muscle afferent drive to the presser response from the triceps surae is lo w in this age group, both in control subjects and in CHF patients. Addition ally, the patients may have a relatively desensitized muscle mechanorecepto r reflex.