Direct evidence from intraneural recordings for increased central sympathetic outflow in patients with heart failure.

TLDR

Heart failure is associated with elevated vascular resistance and neurohumoral drive, including high circulating norepinephrine, though it is unclear whether this reflects increased sympathetic neural activity or altered norepinephrine metabolism. The study aimed to determine whether sympathetic nerve activity is increased in heart failure patients and whether plasma norepinephrine levels correlate with muscle sympathetic nerve activity. Microneurography of the peroneal nerve was used to record muscle sympathetic nerve activity while plasma norepinephrine was measured in heart failure patients and normal controls. Resting muscle sympathetic nerve activity was markedly higher in heart failure patients compared to controls and correlated strongly with plasma norepinephrine, while neither was related to systemic vascular resistance, cardiac index, left ventricular ejection fraction, or heart rate, but both correlated positively with left ventricular filling pressures and mean right atrial pressure. Abstract truncated at 250 words.

Abstract

Patients with heart failure have increased vascular resistance and evidence for increased neurohumoral drive. High levels of circulating norepinephrine are found in patients with heart failure, but it is not known whether they reflect increased sympathetic neural activity or result from altered synthesis, release, or metabolism of norepinephrine. We used microneurography (peroneal nerve) to directly record sympathetic nerve activity to muscle (mSNA) and also measured plasma norepinephrine levels in patients with heart failure and in normal control subjects. Our goal was to determine whether sympathetic nerve activity is increased in patients with heart failure and whether plasma norepinephrine levels correlate with levels of mSNA in heart failure. Resting muscle sympathetic nerve activity in 16 patients with moderate to severe heart failure (54 +/- 5 bursts/min, mean +/- SE) was significantly higher (p less than .01) than the levels of activity in either nine age-matched normal control subjects (25 +/- 4 bursts/min) or 19 "young" normal control subjects (24 +/- 2 bursts/min). We found a significant correlation between plasma norepinephrine levels and mSNA (r = .73, p less than .05). Neither mSNA nor plasma norepinephrine levels correlated with total systemic vascular resistance, cardiac index, left ventricular ejection fraction, or heart rate. However, both mSNA and plasma norepinephrine levels showed significant positive correlations (p less than .05) with left ventricular filling pressures (r = .80, mSNA vs filling pressures; r = .82, norepinephrine levels vs filling pressures) and mean right atrial pressure. (ABSTRACT TRUNCATED AT 250 WORDS)