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

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 980 nm, 1210 nm, and 1700 nm to study the ability to damage renal nerves without causing injury to non-target tissue structures like the endothelium. Then, a 980 nm 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 980 nm, 1210 nm, and 1700 nm. In vitro laser denervation studies at 980 nm 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 1210 nm and 1700 nm 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 980 nm laser (powers ranging from 2 to 4 W, 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 980 nm 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 1210 nm and 1700 nm lasers with the current treatment parameters. Histochemical analysis of in vivo laser treatments in ovine renal arteries using a focused 980 nm laser show clear evidence of renal nerve damage with depths of damage extending > 1.5 mm from the artery wall. Sections with laser-induced damage to the media/adventitia at depths of > 1 mm 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.

Hydroperitoneum-facilitated EUS-guided peritoneal entry and closure of alternate access sites for NOTES.

BACKGROUND: Access sites other than the anterior gastric wall may provide improved ergonomics for natural orifice transluminal endoscopic surgery (NOTES). Endoscopic ultrasound (EUS) guidance significantly reduces, but does not eliminate, risk of access through these alternate sites. This study evaluates the utility of hydroperitoneum as an adjunct to EUS-guided access and closure of alternate access sites for NOTES. METHODS: Access and closure procedures were initially performed with EUS guidance alone, and subsequently, because of complications resulting from this technique, the procedures were performed with the aid of a transabdominal hydroperitoneum. RESULTS: In this nonrandomized study, 6 access and closure procedures performed with EUS guidance alone resulted in 4 complications. After modifying the technique to incorporate pre-access hydroperitoneum, 7 EUS-guided access and closure procedures were performed without significant complications. CONCLUSIONS: Hydroperitoneum appears to be an effective adjunct to ensure the safety of EUS-guided peritoneal entry and closure of alternate access sites for NOTES.

Endoscopic full-thickness resection of gastric lesions using a novel grasp-and-snare technique: evaluation in a porcine survival model.

BACKGROUND: Endoscopic full-thickness resection (EFTR) is a less-invasive method of en bloc removal of gastrointestinal tumors. In a previous nonsurvival animal experiment, the feasibility of a novel grasp-and-snare EFTR technique using a prototype tissue-lifting device was demonstrated. The objective of this study was to evaluate the safety and outcomes of this EFTR method in a porcine survival model. METHODS: EFTR of model stomach tumors was performed in seven pigs using a double-channel endoscope with a prototype tissue-lifting device through one channel and snare through the other. The lifting device was advanced through the snare loop and anchored to the gastric wall adjacent the model tumor. The lifting device was then partially retracted into the endoscope, causing the target tissue, including tumor, to evert into the gastric lumen. The open snare was then placed beyond the tumor around uninvolved gastric tissue. Resection was performed by delivering an electrosurgical current through the snare. EFTR defects were closed by using tissue anchors. After an intended 10-day observation period, the pigs were euthanized and necropsy was performed. RESULTS: All seven resections were successful with negative gross margins. No immediate complications occurred. Two defect closures failed during the early postoperative period, leading to infectious complications. The remaining intact closures were complicated by adjacent ulcers, one of which resulted in hemorrhage. CONCLUSIONS: Endoscopic full-thickness resection of gastric lesions using the grasp-and-snare technique is feasible in pigs. In this experiment, complications related to closure were significant. Further evaluation and modification of closure technique is necessary before studying this method of EFTR in humans.