Renal denervation using focused infrared fiber lasers: A potential treatment for hypertension

Abstract

Background and Objective Renal denervation has recently become of great interest as a potential treatment for resistant hypertension. Denervation techniques using radio frequency (RF) or ultrasound energy sources have already been explored in literature. In this study, we investigate the use of lasers as a potential energy source for renal denervation. In vitro studies are performed in porcine/ovine renal arteries with focused laser beams at 980nm, 1210nm, and 1700nm to study the ability to damage renal nerves without causing injury to non-target tissue structures like the endothelium. Then, a 980nm laser catheter prototype is built and used to demonstrate in vivo renal denervation in ovine renal arteries. Subjects and Methods This study utilizes fiber coupled infrared lasers at 980nm, 1210nm, and 1700nm. In vitro laser denervation studies at 980nm are performed in both porcine and ovine renal arteries to study the ability of focused laser beams to damage renal nerves without injuring the endothelium. In vitro studies using lasers close to the lipid absorption lines at 1210nm and 1700nm are also performed in porcine renal arteries to study the possibility of selectively damaging the renal nerves by targeting the lipid myelin sheaths surrounding the nerves. Then, a laser catheter prototype is designed and built for in vivo renal denervation in ovine renal arteries using the 980nm laser (powers ranging from 2 to 4W, 5 seconds per exposure). Histochemical evaluations of the frozen sections are performed using methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. Results Histochemical analysis of in vitro laser treatments at 980nm in porcine and ovine renal arteries show clear evidence of laser-induced renal nerve damage without injury to the endothelium and part of the media. No evidence of selective nerve damage is observed using the 1210nm and 1700nm lasers with the current treatment parameters. Histochemical analysis of in vivo laser treatments in ovine renal arteries using a focused 980nm laser show clear evidence of renal nerve damage with depths of damage extending>1.5mm from the artery wall. Sections with laser-induced damage to the media/adventitia at depths of>1mm without injury to the endothelium are also observed. Conclusions We demonstrate the use of focused lasers as an attractive energy source for causing renal nerve damage without injury to the artery wall and thus, may have potential therapeutic applications for conditions such as resistant hypertension, where renal denervation has been shown to be a promising form of treatment. Lasers Surg. Med. 46:689-702, 2014.