EFFECTS OF INTRAVENOUS B-TYPE
NATRIURETIC PEPTIDE (BNP) ON REGIONAL SYMPATHETIC TONE IN PATIENTS WITH CHRONIC
HEART FAILURE AND HEALTHY CONTROLS. H.P. Brunner-La Rocca, D.M. Kaye,
R.L. Woods*# and M.D. Esler. Baker Medical Research Institute,
Prahran, and #Howard Florey Institute, University of Melbourne,
3010, Australia. The effects of
BNP on total and regional activity of the sympathetic nervous system (SNS) have
not yet been investigated in humans. We
assessed cardiac and whole body SNS, using the radiotracer dilution method to
measure noradrenaline spillover, before and after infusion of two doses of BNP
(3 and 15 ng/kg/min) in 12 patients with stable heart failure (HF; EF 24 ± 2%)
and 12 age-matched healthy control subjects.
In addition, renal SNS and haemodynamics were assessed at baseline and
after high dose of BNP. In HF patients,
baseline haemodynamics were compromised and activity of SNS was elevated. Low dose BNP did not change, significantly,
intracardiac pressures, arterial blood pressure or whole body noradrenaline
(NA) spillover (SP) but did reduce cardiac NA SP in both groups by 32±13
pmol/min (P<0.05). High dose BNP
lowered right and left heart pressures in both groups (P<0.05), with no
significant accompanying increases in total or cardiac NA SP. With high dose BNP, renal NA SP remained
virtually unchanged in healthy controls (501±120 to 564±115 pmol/min) but was
substantially reduced in HF patients (976±133 to 656±127, P<0.01). Our results provide strong evidence for a
direct sympathoinhibitory action of BNP in HF patients, particularly in the
kidney but also in the heart. The
cardiac sympathoinhibitory effects of BNP were probably reversed by baroreflex
activation whereas renal sympathoinhibition was maintained despite
cardiopulmonary baroreceptor unloading.
