788 PROFOUND REDUCTION IN SYMPATEHTIC NERVE FIRING PATTERN AFTER RENAL DENERVATION IN RESISTANT HYPERTENSION

Abstract

Objective: Renal denervation (RDN) has been shown to reduce blood pressure (BP) and sympathetic activation in resistant hypertension (RH). The underlying mechanisms involved in sympathetic neural inhibition are unknown. We examined whether RDN may influence differentially sympathetic discharge of vasoconstrictor neurons in patients with RH. Design and method: Standardized office BP, multi-unit and single-unit muscle sympathetic nerve activity (MSNA) measured by microneurography were obtained in 23 patients with RH (57 ± 12yrs) before and 3 months after RDN. Results: Baseline BP averaged 166/74 ± 18/20mmHg despite the use of 4.8 ± 2.0 antihypertensive drugs. RDN was performed with an average of 9.4 ± 1.8 total ablations. SBP decreased significantly by -11 ± 18 mmHg (p < 0.01) and DBP by -5 ± 10 mmHg (p < 0.05). While multi-unit MSNA was only moderately reduced (78 ± 17 vs 71 ± 17bursts/100 heart beats (hb); p < 0.05), all properties of single-unit MSNA including firing rates of individual vasoconstrictor fibers (44 ± 25 vs 27 ± 17 spikes/100hb; p < 0.01), firing probability (31 ± 12 vs 22 ± 12% of hb; p < 0.02), and the multiple firing incidence of single units (9 ± 8 vs 4 ± 4% of hb; p < 0.05) were substantially reduced at 3 month follow up. The DBP reduction was significantly related to multi-unit MSNA decrease (r = 0.54; p < 0.01), but not to single-unit firing pattern. Conclusions: In patients with RH, RDN results in a marked and rapid reduction in the single-unit sympathetic firing discharge pattern of active vasoconstrictor fibres that appears to be more pronounced than multi-unit MSNA reduction. Whether early assessment of the changes in single-unit firing characteristics may be useful to predict the BP response to RDN warrants further investigation.