Abstract 12272: Ultrasound Mediated Renal Sympathetic Denervation
The renal sympathetic nerves have been identified as a major contributor to the complex physiology of hypertension in both experimental models and humans. Renal Sympathetic Denervation (RSD) has been demonstrated to be an effective method for treating patients with hypertension who have been refractory to medical therapy. Recently, catheter-based renal artery radiofrequeny ablation has been shown to safely and effectively attenuate renal sympathetic nerve activity, resulting in significant reduction in norepinephrine spillover and a substantial and sustained decrease in blood pressure in patients with refractory hypertension. We sought to evaluate if RSD could be accomplished with externally applied focused ultrasound. The novel applicator incorporates an anatomically customized phased-array ultrasound transducer to generate and focus therapeutic energy to the depth of the renal artery, and an ultrasound imaging transducer to facilitate locating, targeting and tracking the renal artery for treatment. Following preliminary feasibility studies in an open animal model, studies were performed using the external applicator system in Yorkshire swine. After locating the renal artery in an appropriate acoustic window using duplex ultrasound, single-sided therapy was directed in a single plane perpendicular to the renal artery in multiple rows. Energy dosing between 50-60 watts at 4 centimeter depth was targeted at seventeen 10x1.5 millimeter regions. At 1 and 6 weeks following therapy, cortex biopsies were obtained from the kidney on the treatment and control side to determine norepinephrine (NE) concentrations. Results demonstrated a 71±17% reduction in NE levels at 1 week when compared to contralateral measurements (p=0.003).The reduction in NE was persistent at 6 weeks when compared to baseline values (62 ± 10%). Histology at 6 weeks following therapy demonstrated neurolysis of the of the peri-vascular nerve bundles. These results demonstrate the feasibility of targeted external ultrasound for renal sympathetic denervation in an animal model and support further investigation in patients with hypertension.
- © 2011 by American Heart Association, Inc.