Innervation Patterns May Limit Response to Endovascular Renal Denervation
What is the effect of renal neural network anatomy on renal denervation treatment efficacy?
A multi-electrode radiofrequency (RF) catheter (15 W/60 s) treated eight renal arteries (Group 1). Arteries and kidneys were harvested 7 days post-treatment. Renal norepinephrine (NEPI) levels were correlated with ablation zone geometries and neural injury. Nerve and ganglion distributions and sizes were quantified at discrete distances from the aorta and compared with 16 control arteries (Group 2).
Nerve and ganglia distributions varied with distance from the aorta (p < 0.001); 75% of nerves fell within a circumferential area of 9.3, 6.3, and 3.4 mm of the lumen at 0.3, 3.0, and 6.0 mm from the aorta. Efficacy (NEPI 37 ng/g) was observed in only one of eight treated arteries where ablation involved all four quadrants, reached a depth of 9.1 mm, and affected 50% of nerves. In seven treated arteries, NEPI levels remained at baseline values (620-991 ng/g), ≤20% of the nerves were affected, the ablation areas were smaller (16.2 ± 10.9 mm2), and present in only 1-2 quadrants at maximal depths of 3.8 ± 2.7 mm.
The authors concluded that renal denervation procedures that do not account for asymmetries in renal periarterial nerve and ganglia distribution may miss targets and fall below the critical threshold for effect.
This study suggests that renal denervation therapies which assume symmetric neural networks run the real risk of missing nerves when unitary lesions are imposed. This is particularly true for the renal ostium which, though an attractive target, imposes significant challenges. Ganglia and nerves are more abundant at the renal ostium, but are located farther from the lumen and present in all four quadrants, not just the superior aspect. Penetration depths, which ablate along the length of the renal artery, may be ineffective at the ostium. There appears to be a need to match future treatment strategies with increasing understanding of the target anatomy for renal denervation therapies.
Keywords: Ganglia, Electrodes, Renal Artery, Denervation, Norepinephrine
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