Background RF renal denervation protocols employ uniform treatment settings regardless of electrode location guided by the premise of symmetric innervation patterns. We examined asymmetries in renal arterial-ostium innervation and their effects on RF treatment efficacy.
Methods Nerve and ganglion sizes and distributions were characterized in 16 porcine renal arteries at 3 discrete distances from the aorta. RF ablation was performed in the renal ostium of another 8 porcine arteries using a prototype renal/crescent multi-electrode RF catheter (Biosense Webster, CA) & treatments were confirmed by angiography. Renal norepinephrine (NEPI) levels were correlated with ablation zone geometries & nerve and ganglia injury 7d post denervation.
Results Nerves & ganglia were more abundant but smaller and more distant from the lumen at locations closest to the aorta. At all 3 distances from the aorta, nerves and ganglia were distributed across all 4 quadrants.
Efficacy was observed in 1 of 8 treated arteries where ablation area was 99.1mm2 and involved all 4 quadrants at a maximal depth of 9.1mm affecting 50% of nerves, reducing NEPI (37ng/g). In the other 7 arteries, no efficacy was observed, fewer than 20% of the nerves were affected, the ablation areas were smaller (16.2±10.9mm2) and present in only 1-2 quadrants at maximal depths of 3.8±2.7mm, and renal NEPI levels remained at baseline (620-991ng/g). Half of ablation zones did not contain ganglia, and the rest only 1 or 2 ganglia.
Conclusion Renal denervation therapies which assume symmetric neural networks run the real risk of missing nerves when solitary lesions are imposed. This is especially true for the renal ostium which, though an attractive target, imposes significant challenges. As we move forward with this emerging technology we need to match treatment strategies with increasing understanding of the target anatomy.
