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. 2015 Jul;28(7):909-14.
doi: 10.1093/ajh/hpu258. Epub 2015 Jan 8.

Catheter-Based Radiofrequency Renal Denervation: Location Effects on Renal Norepinephrine

Jeffrey R Henegar  1 , Yongxing Zhang  2 , Cary Hata  2 , Irvin Narciso  2 , Michael E Hall  3 , John E Hall  4
Affiliations

Catheter-Based Radiofrequency Renal Denervation: Location Effects on Renal Norepinephrine

Jeffrey R Henegar et al. Am J Hypertens. 2015 Jul.

Abstract

Background: Clinical studies indicate that blood pressure (BP)-lowering effects of radiofrequency (RF) renal denervation (RD) are sustained for up to 2 years, although a recent clinical trial failed to find a major effect compared to sham treatment. In most previous studies, the efficacy of RD has not been assessed. The current study determined whether RD in different regions of the renal artery causes different degrees of RD as assessed with renal norepinephrine (NE) levels.

Methods and results: Unilateral RD was performed on 14 pigs divided into 3 groups: RD near the ostium, in the main renal artery near the bifurcation, and in extrarenal branches of the renal artery. After 2 weeks post-RD, the pigs were euthanized, renal cortex tissue was collected for NE measurement, and renal arteries were prepared for histological analysis. Renal NE decreased by 12% with RD at the ostium, 45% with RD near the bifurcation in the main renal artery, and 74% when RD was performed in extrarenal artery branches. The number of renal nerves was greatest in extrarenal branches and in the main artery compared to the ostium and the average distance from the lumen was greatest for nerves at the ostium and least at the branches.

Conclusions: RF RD lowers renal NE more significantly when performed in branches of the renal artery closer to the kidney. Increased efficacy of RF RD in extrarenal arterial branches may be due to the greater number of nerves in close proximity to the artery lumen in the branches.

Keywords: blood pressure; hypertension; norepinephrine; radiofrequency ablation; renal denervation; renal nerves..

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Figures

Figure 1.
Figure 1.
Areas of denervation along the renal artery. Locations used for RD (A) and the approximate areas defined for the histological analysis (B). Abbreviation: RD, renal denervation.
Figure 2.
Figure 2.
Renal arteriograms. Renal arteriograms showing the renal artery with contrast (A), the RD catheter basket seated in the renal artery (B), some vasospasm immediately following the application of the radiofrequency signal (C), and the resolution of the vasospasm (D). Abbreviation: RD, renal denervation.
Figure 3.
Figure 3.
Renal tissue norepinephrine. Renal tissue norepinephrine levels measured from non-denervated kidneys (control) and denervated kidneys (RD). Kidneys were denervated at the ostium, the main artery, or in the branches of the renal artery. *P < 0.05, NS = not significant. Abbreviation: RD, renal denervation.
Figure 4.
Figure 4.
Total number of nerves in different sections of the renal artery. Total number of nerves observed in all sections from the proximal, middle, and distal sections of the renal artery.
Figure 5.
Figure 5.
Cross-sectional area of nerves in different sections of the renal artery. Nerve cross-sectional area measured in sections coming from the proximal, middle, and distal sections of the renal artery. *P < 0.05 vs. distal.
Figure 6.
Figure 6.
Nerve distance from lumen–endothelial border. Nerve distance from the renal artery endothelial–lumen border measured in sections coming from the proximal, middle, and distal areas of the renal artery. *P < 0.05 vs. proximal; ^P < 0.05 vs. middle; @P < 0.05 vs. distal.
Figure 7.
Figure 7.
Cumulative percentage of nerves. Cumulative percentage of nerves from the renal artery endothelial–lumen interface for the different areas of sections analyzed.
See this image and copyright information in PMC

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