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Radio frequency (RF) catheter-based renal artery nerve ablation is under investigation for the treatment of patients with drug- resistant hypertension. Recent clinical results suggest that a four quadrant coverage is necessary to achieve optimal denervation. These results also suggest that increasing the number of ablation lesions improves denervation effectiveness. In the present study we evaluated the lesion characteristics and degree of arterial, circumferential coverage with RF ablation using the EnligHTNTM Multi-Electrode Renal Denervation System in the domestic swine animal model.
Methods and Results
Theoretical modeling and preclinical ablation were conducted to develop an arterial lesion coverage algorithm. Twenty three domestic swine were randomly assigned to either treatment (ablation) groups or sham procedure groups. Animals in the treatment groups received simultaneous RF energy delivery from a four electrode basket catheter; whereas animals in the sham procedure groups were either naïve untreated animals or received only balloon dilation with no energy delivery. In the treatment arm two RF applications (8 lesions) were delivered per renal artery. The animals were terminated at three timepoints: acute, 30, and 90 days after the procedure. Acute necropsy findings showed four well-demarcated transmural lesions per RF application site on both luminal and adventitial surfaces of each renal artery. Observed lesion dimensions were 3.0 ± 0.4 width x 2.1 ± 0.3 length mm. The number of lesions needed for circumferential arterial coverage increased with the renal artery diameter as follows:
Renal artery diameter (mm)Lesions needed for circumferential coverage
44.4, 55.5, 66.6, 77.7, 88.8
Kidneys were analyzed for norepinephrine (NE) levels at the time of sacrifice. Baseline NE levels were 367±119.76 in the naïve animals and 342±43 ng/g in the sham procedure group. The values decreased to 162±15 (56% decrease)at 30 days, and 164±43 ng/g (55% decrease) at 90 days in the 30, and 90 day RF treated groups, respectively. Immunohistochemistry and H&E stains indicated fiber interruption, fiber injury or inflammation and functional derailment in all affected fibers.
Renal nerve ablation using the EnligHTNTM Multi-Electrode Denervation System provides uniform transmural lesions with longitudinal, circumferential arterial coverage. In order to obtain full circumferential coverage, the number of lesions needed increases with the renal artery diameter.