Influence of the metaboreflex on arterial blood pressure in heart failure patients

Abstract

Background Feedback from active locomotor muscles contributes to the exercise pressor response in healthy humans, and is thought to be more prominent in heart failure (HF). The purpose of this study was to examine the influence of metaboreflex stimulation on arterial pressure in HF. Methods Eleven HF patients (51±15yrs, NYHA Class I/II, LVEF 32±9%) and 11 controls (CTL) (42±9yrs) were recruited. Participants completed two exercise tests on separate days: 1) symptom limited graded exercise test; and 2) constant work rate cycling (60% peak oxygen consumption, V̇O2) for 4 min with 2 min passive recovery. Recovery was randomized to normal or locomotor muscle regional circulatory occlusion (RCO). V̇O2, mean, systolic, and diastolic blood pressure (MAP, SBP, and DBP) and heart rate (HR) were measured at rest, end-exercise and recovery. O2 pulse (V̇O2 /HR) and the rate pressure product (RPP = HR × SBP) were calculated. Results In response to RCO, MAP and SBP increased in HF compared with CTLs (6.8±5.8% vs −3.0±7.8%, p<0.01 and 3.4±6.4% vs −12.7±10.4%, p<0.01, respectively), with no difference in diastolic pressure (p=0.61). HF patients had a smaller reduction in HR and RPP, but also displayed a larger decrease in O2 pulse consequent to locomotor metaboreflex stimulation (p<0.05, for all). Conclusion RCO resulted in a markedly increased pressor response in HF relative to CTL, due primarily to an increase of SBP and attenuated cardiac recovery as noted by the persistent elevation in HR.

Influence of the Metaboreflex on Pulmonary Vascular Capacitance in Heart Failure

“…Participant characteristics are presented in Table 1, and have been reported previously during testing of a separate hypothesis in HF (16). Heart failure patients were NYHA class I (n=4) or II (n=7).…”

“…This study protocol has been published previously by our group for the separate study of an a priori determined hypothesis (16). Therefore, in brief, this study consisted of two separate days of exercise testing procedures, in an environmentally controlled physiological laboratory, separated by ≥48-hours.…”

“…Growing evidence in support of the “muscle hypothesis” suggests that feedback from group III/IV skeletal muscle nerve fibers contributes to altered ventilatory and peripheral arterial pressure control during exercise in HF (16, 26-28). Post-exercise regional circulatory occlusion (RCO) is a valid non-invasive technique used to selectively study the influence of group IV neural feedback from skeletal muscle (i.e., metaboreflex) on cardiovascular responses in humans (32).…”

“…Post-exercise regional circulatory occlusion (RCO) is a valid non-invasive technique used to selectively study the influence of group IV neural feedback from skeletal muscle (i.e., metaboreflex) on cardiovascular responses in humans (32). Activation of the metaboreflex influences sympathetically mediated vasoconstriction and augmented ventilation that leads to ventilatory inefficiency in HF (16, 27). In contrast, the metaboreflex has a favorable influence on peripheral vascular conductance and both ventilatory and cardiac function during exercise in healthy individuals (2, 6-9).…”

“…As such, because of the clinical implications of secondary PH in HF, the afterload sensitivity of systolic HF patients, and the associations between metaboreflex activation and increased peripheral arterial pressure in this population (16); the aim of this study was to examine the influence of the locomotor muscle metaboreflex, via post-exercise RCO, on CircP and GX CAP in HF. We hypothesized that isolation of the locomotor muscle metaboreflex during post-exercise recovery would contribute to the attenuation of both CircP and GX CAP in HF patients.…”