Beta radiation for renal nerve denervation: initial feasibility and safety

Abstract

In small clinical trials, sympathetic renal denervation using radiofrequency (RF) energy shows promise in treating resistant hypertension. However, the RF procedure is lengthy and is associated with pain during ablation. Vascular brachytherapy, a proven treatment for in-stent restenosis, has the potential to cause nerve fibrosis. The purpose of the present study was to assess the safety and feasibility of renal artery brachytherapy for sympathetic renal denervation. A total of 10 normotensive domestic swine underwent vascular brachytherapy to left and right renal arteries using the Beta-Cath 3.5 Fr delivery system at doses of 25 Gy (n=8) and 50 Gy (n=8) at 2 mm from the source centre. These groups were compared to untreated arteries that served as control (n=4). Follow-up obtained at one or two months included angiogram, intravascular ultrasound, and histopathology analysis. The vascular brachytherapy procedure was safe and no apparent angiographic or ultrasound injuries to the vessel were seen. Histology showed a varying degree of thermal injury more pronounced in the 50 Gy group. The majority of examined nerves showed some degree of injury; there was a dose-related effect on nerve injury severity. There were varying degrees of arteriolar changes in the examined sections, with most showing a 2-20% degree of endothelial cell loss. This initial feasibility and safety study of renal nerve denervation, mediated by low and intermediate β-radiation dosages, indicates that this approach can cause nerve fibrosis while avoiding significant damage to the renal artery.