Shirley Alvarez

BACKGROUND: Transcatheter renal denervation (RDN) remains inconsistent despite developments in ablation technologies, due to the lack of an intraprocedural physiological end point. The aim of this study was to identify if aorticorenal ganglion (ARG) guided RDN using microwave (MW) catheter leads to more consistent denervation outcomes compared with empirical MW ablation. METHODS: Pigs underwent sham procedure (n=8) or bilateral RDN using an in-house built open-irrigated MW catheter. Before denervation, ipsilateral ARG pacing was performed leading to renal artery vasoconstriction. MW ablation group (MW-group; n=7) received 1 ablation (100–120 W for 360 seconds) in the mid-main renal artery based on artery caliber. ARG-guided-MW ablation group (ARG-MW-group; n=7) was permitted an additional ablation more distally or at higher power until a vasoconstrictive response was abolished. Animals were euthanized at 4 to 5 weeks post-procedure. RESULTS: ARG pacing caused an ipsilateral reduction in renal artery caliber from 4.67 to 4 mm; P =0.0006 in MW-group and 4.8 to 3.9 mm; P =0.001 in ARG-MW-group. Repeat ARG pacing at euthanasia led to a reduction in renal artery caliber in MW-group from 5.1 to 4.8 mm; P =0.006, but not in ARG-MW-group from 4.88 to 4.55 mm; P =0.08. There were no differences in ablation injury volumes between the groups. Compared with undenervated sham controls, ARG-MW-RDN versus MW-RDN caused median reductions in viable nerve area (antityrosine hydroxylase staining) at 4 to 5 weeks by 92.6% (interquartile range, 0.94–19.59%; P P =0.006) and median renal cortical norepinephrine content by 68.06% (interquartile range, 27.16–38.39%; P P =NS). CONCLUSIONS: ARG pacing serves as a physiological procedural end point to guide MW denervation to improve denervation outcomes.

Background: Transcatheter renal denervation (RDN) has had inconsistent efficacy and concerns for durability of denervation. We aimed to investigate long‐term safety and efficacy of transcatheter microwave RDN in vivo in normotensive sheep in comparison to conventional radiofrequency ablation. Methods and Results: Sheep underwent bilateral RDN, receiving 1 to 2 microwave ablations (maximum power of 80–120 W for 240 s–480 s) and 12 to 16 radiofrequency ablations (180 s–240 s) in the main renal artery in a paired fashion, alternating the side of treatment, euthanized at 2 weeks (acute N=15) or 5.5 months (chronic N=15), and compared with undenervated controls (N=4). Microwave RDN produced substantial circumferential perivascular injury compared with radiofrequency at both 2 weeks [area 239.8 (interquartile range [IQR] 152.0–343.4) mm ² versus 50.1 (IQR, 32.0–74.6) mm ² , P P 2 versus 5.0 (IQR, 1.4–7.3) mm ² , P =0.025; depth 5.9 (IQR, 1.9–8.8) mm versus 3.1 (IQR, 1.2–4.1) mm, P =0.005] using mixed models. Renal denervation resulted in significant long‐term reductions in viability of renal sympathetic nerves [58.9% reduction with microwave ( P =0.01) and 45% reduction with radiofrequency ( P =0.017)] and median cortical norepinephrine levels [71% reduction with microwave ( P P <0.001)] at 5.5 months compared with undenervated controls. Conclusions: Transcatheter microwave RDN produces deep circumferential perivascular ablations without significant arterial injury to provide effective and durable RDN at 5.5 months compared with radiofrequency RDN.