Influence of the Metaboreflex on Pulmonary Vascular Capacitance in Heart Failure

PURPOSE: An impaired metaboreflex is associated with abnormal ventilatory and peripheral vascular function in heart failure (HF), whereas its influence on cardiac function or pulmonary vascular pressure remain unclear. We aimed to assess whether metabolite-sensitive neural feedback (metaboreflex) from locomotor muscles via post-exercise regional circulatory occlusion (RCO) attenuates pulmonary vascular capacitance (GXCAP) and/or circulatory power (CircP) in HF patients. METHODS: Eleven HF patients (NYHA class: I/II; ages, 51±15; ejection fraction: 32±9%) and 11 age and gender matched controls (ages, 43±9) completed three cycling sessions (four-minutes, 60% peak oxygen uptake [VO2]). Session one: control trial=normal recovery (NR). Sessions two or three: bilateral upper-thigh pressure tourniquets inflated suprasystolic at end-exercise (RCO) for 2-minute recovery with or without inspired CO2 (RCO+CO2) (randomized). Mean arterial pressure (MAP), heart rate, and VO2 were continuously measured. Estimates of central hemodynamics; CircP=(VO2×MAP)/weight, oxygen pulse index (O2pulseI=(VO2/heart rate)/body surface area), and GXCAP=O2pulseI×end-tidal partial pressure CO2 were calculated. RESULTS: At rest and end-exercise, CircP and GXCAP were lower in HF versus controls (P0.05). At 2-minute recovery, GXCAP was lower during RCO versus NR in both groups (72±23 versus 98±20 and 73±34 versus 114±35 mL[BULLET OPERATOR]beat[BULLET OPERATOR]mm Hg[BULLET OPERATOR]m, respectively; P0.05). Differences (% and Δ) between baseline and 2-minute recovery amongst transients suggest the metaboreflex attenuates GXCAP in HF. Differences (% and Δ) between baseline and 2-min recovery amongst transients suggest the metaboreflex may attenuate CircP in controls. CONCLUSION: The present observations suggest locomotor muscle metaboreflex activation may influence CircP in controls but not in HF. However, metaboreflex activation may evoke decreases in GXCAP (increased pulmonary vascular pressures) in HF and controls.