Oral Presentation Neuropathophysiology - an ISH satellite 2012

Early and pronounced reduction in single sympathetic nerve firing properties in response to renal denervation in patients with resistant hypertension (#43)

Dagmara Hering 1 2 , Elisabeth Lambert 1 , Petra Marusic 1 , Carolina Ika-Sari 1 , Gavin Lambert 1 , Murray Esler 1 , Markus Schlaich 1
  1. Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
  2. Department of Hypertension and Diabetology, Medical University of Gdansk, Gdansk, Poland

BACKGROUND: Renal denervation (RDN) resulted in blood pressure (BP) and muscle sympathetic nerve activity (MSNA) reduction in resistant hypertension (RH). The mechanisms underlying sympathetic neural inhibition are unknown. We examined whether RDN differentially influences sympathetic discharge of vasoconstrictor neurons in RH. 

METHODS: Standardized office BP, multi-unit and single-unit MSNA were measured at baseline and at 3 month follow-up in 35 consecutive patients with RH. 25 patients underwent RDN and 10 patients served as controls (non-RDN). 

RESULTS: Baseline BP averaged 165/91 mmHg (RDN) and 161/87 mmHg (non-RDN) despite use of an average of four antihypertensive drugs. Mean office BP decreased significantly by -11/-5 mmHg for SBP (p<0.01) and DBP (p<0.05) in RDN, but not in non-RDN at 3 month follow-up. RDN moderately decreased multi-unit MSNA (79±3 vs. 73±4 bursts/100heart beats (hb);p<0.05), while all properties of single-unit MSNA including firing rates of individual vasoconstrictor fibers (43±5 vs. 27±3 spikes/100hb;p<0.01), firing probability (30±2 vs. 22±2% of hb;p<0.02), and the multiple firing incidence of single units (8±1 vs. 4±1% per hb;p<0.05) were substantially reduced at follow-up. The DBP reduction was significantly related to multi-unit MSNA decrease (r=0.52;p<0.01), but not to single-unit firing pattern. There were no changes in multi-unit and single-unit MSNA in non-RDN group at follow-up.

 CONCLUSIONS: RDN results in profound and rapid reduction in firing properties of single sympathetic vasoconstrictor fibre that appears more pronounced than multi-unit MSNA inhibition. Whether earlier changes in single-unit firing patterns may predict the BP response to RDN requires further exploration.

DISCLOSURE: This study was funded in part by grants from the NHMRC, the Victorian Government’s Operational Infrastructure Support Program and Medtronic. Dres Schlaich, G Lambert and Esler are supported by career fellowships from the NHMRC and are investigators in studies sponsored by Medtronic. Dr Hering was awarded by Fellowship from the Foundation for Polish Science KOLUMB/2010-1.