Reflex neural oversignaling sensitive to muscle by-products (ergoreflex) causes exercise hyperventilation in heart failure (HF). We probed whether an improved endothelial function with sildenafil intake may prevent this effect. In 16 chronic heart failure patients and 16 normal subjects, before and after sildenafil intake (50 mg) or placebo, we measured ergoreflex, flow-mediated brachial artery dilation (FMD, an index of endothelial function), and, during maximal exercise, the slope of ventilation to carbon dioxide production (VE/VCO 2, an index of ventilatory efficiency), the ratio of changes in O 2 uptake (VO 2) versus work rate (WR) (ΔVO 2/ΔWR, an index of aerobic efficiency). After sildenafil intake, patients, unlike controls, showed a significant decrease in ergoreflex and VE/VCO 2 slope and an increase in FMD and ΔVO 2/ΔWR. Ergoreflex changes with sildenafil intake correlated with those in FMD and VE/VCO 2. Phosphodiesterase-5 inhibition, by improving endothelial activity and muscle perfusion, modulates signaling and improves ventilatory and aerobic efficiencies, potentially indicating a novel pathway in the HF therapeutic management.
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