Abstract 14033: Hemodynamic Responses and Histological Effects of Radiofrequency Catheter Ablation to Renal Artery Sympathetic Nerve
Background: Radiofrequency (RF) catheter ablation of the renal artery is therapeutic in patients with drug-refractory essential hypertension, although details of the therapeutic mechanisms have not been clarified.
Method: Under general anesthesia, an open irrigation catheter was inserted into either the left or right renal artery in 8 dogs. RF current (17±2 Watts, 30 seconds, 5 times) was delivered to one renal artery. Electrical stimulation of the autonomic nerves (20-Hz, 5-ms, 15-mA) was applied to each renal artery, before and after the renal artery RF ablation. Blood pressure (BP), heart rate, parameters of heart rate variability (HRV) and serum catecholamines were analyzed, and the renal arteries were examined histologically.
Results: Before RF ablation, electrical stimulation of either renal artery increased BP, from 146±17/85±17 to 172±23/102±18 mmHg. After RF ablation, BP increased similarly when the non-ablated renal artery was electrically stimulated (increased to 173±24/102±25 mmHg), though the rise in BP was markedly attenuated when the ablated renal artery was stimulated (increased to 152±20/86±15 mmHg). Serum epinephrine and norepinephrine and LF/HF ratio of HRV increased when electrical stimulation was applied a) before RF ablation and b) to the non-ablated renal artery after RF ablation (epinephrine increased from 0.04±0.03 and 0.44±0.33 ng/dl, norepinephrine from 0.04±0.02 to 0.17±0.08 ng/dl, and LF/HF ratio from 0.20 ± 0.16 to 1.36 ± 2.10), though changed minimally when the ablated renal artery was stimulated (epinephrine increased to 0.12±0.11 ng/dl, norepinephrine to 0.07±0.04 ng/dl, and LF/HF ratio to 0.42 ± 0.34). Angiograms revealed no stenosis or injury to any vessel, either before or after RF ablation Hematoxylin-eosin stain and neurofilament immunostain showed no apparent injury to the renal artery and its nerve fibers.
Conclusions: Electrical stimulation of the renal arterial autonomic nerves increases BP via an increase in central sympathetic nervous activity, without causing structural injury to the renal artery. This response might be useful in determining an optimal ablation site and endpoint of renal artery RF ablation.
- © 2012 by American Heart Association, Inc.