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

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)