Abstract 10528: Exaggerated Inspiratory Muscle Metaboreflex in Heart Failure with Preserved Ejection Fraction

Abstract

Introduction: Heart failure patients with preserved ejection fraction (HFpEF) may exhibit inspiratory muscle dysfunction potentially contributing to exercise intolerance. Activation of neural afferents in response to inspiratory muscle contraction (metaboreflex) elicits increases in mean arterial pressure (MAP) and leg vascular resistance (LVR) through enhanced sympathetic outflow leading to decreases in leg blood flow (LBF) in healthy humans. It is unknown if HFpEF patients exhibit exaggerated cardiovascular responses to inspiratory muscle metaboreflex activation. Hypothesis: We hypothesize that patients with HFpEF will exhibit a greater increase in MAP and LVR with a decrease in LBF during inspiratory muscle metaboreflex activation than controls. Methods: HFpEF patients (n=15, 10M/5W, 69±10 yrs; 33±4 kg/m2) and controls (n=14; 10M/4W; 70±8 yrs; 28±4 kg/m2) performed inspiratory resistive breathing tasks (IRBT) at 2% and 60% of their maximal inspiratory pressure. During the IRBTs, the breathing frequency was 20 breaths/min with a 50% duty cycle. At rest and during the IRBTs, MAP was measured by photoplethysmography, venous norepinephrine was measured, LBF was measured by near-infrared spectroscopy and indocyanine green dye injections, and LVR was calculated. Results: During the 2% IRBT, there were no differences between groups in the changes from rest in MAP (HFpEF: 2±4 vs. CTL: 3±4 mmHg) or LBF (HFpEF: 1±14 vs. CTL: 1±12%) (both, p>0.05). During the 60% IRBT, venous norepinephrine increased from rest in HFpEF and controls (p<0.05), while no differences existed between groups (p>0.05). During the 60% IRBT, HFpEF patients, compared to controls, exhibited a greater increase from rest in MAP (HFpEF: 16±7 vs. CTL: 10±6 mmHg) and LVR (HFpEF: 76±45 vs. CTL: 32±19%) coupled with a greater decrease in LBF (HFpEF: -32±14 vs. CTL: -17±9%) (all, p<0.05). Conclusions: These data indicate that patients with HFpEF exhibit exaggerated cardiovascular responses with inspiratory muscle metaboreflex activation compared to healthy individuals. These findings have important implications for the integrative physiology of exercise in HFpEF patients.