Abnormal neurovascular control during exercise is linked to heart failure severity

The purpose of this study was to determine if abnormalities of sympathetic neural and vascular control are present in mild and/or severe heart failure (HF) and to determine the underlying afferent mechanisms. Patients with se vere HF, mild HF, and age-matched controls were studied. Muscle sympathetic nerve activity (MSNA) and forearm vascular resistance (FVR) in the nonexer cising arm were measured during mild and moderate static handgrip. MSNA dur ing moderate handgrip was higher at baseline and throughout exercise in sev ere HF vs. mild HF (peak MSNA 67 +/- 3 vs. 54 +/- 3 bursts/min, P< 0.0001) and higher in mild HF vs. controls (33 +/- 3 bursts/ min, P< 0.0001), but t he change in MSNA was not different between the groups. The change in FVR w as not significantly different between the three groups during static exerc ise. During isolation of muscle metaboreceptors, MSNA and blood pressure re mained elevated in normal controls and mild HF but not in severe HF. During mild handgrip, the increase in MSNA was exaggerated in severe HF vs. contr ols and mild HF, in whom MSNA did not increase. In summary, the increase in MSNA during static exercise in severe HF appears to be attributable to exa ggerated central command or muscle mechanoreceptor control, not muscle meta boreceptor control.