Noninvasive Renal Sympathetic Denervation By MRI-guided High-intensity Focused Ultrasound In A Hypertension Canine Model

Backgrounds and Objective: At present, the hypertension and itscomplications is among the leading causes of morbidity and mortalityworldwide. Although clinical experiments of catheter-based renalsympathetic denervation show that the moderate efficacy of both theradiofrequency ablation catheter and ultrasound catheters, there arelimitations and potential safety concerns associated with complications andimpairments to renal artery. So it is necessary to explore a more simple，safeand efficiency technology for renal sympathetic denervation. Based onprimary experiment of noninvasive renal sympathetic denervation byextracorporeal high-intensity focused ultrasound in a preclinical caninemodel, this study was to evaluate the efficacy and safety of MRI-guidedhigh-intensity focused ultrasound for renal sympathetic denervation in thecanine model of hypertension.Methods: We used fifteen healthy canines as experimental subjects.The10neurogenic hypertension canines were establishing by compressingvagus nerve.1week after establishing punctate HIFU ablation (1mm pitch) with300W of power and600J of energy guided by MR were performed onbilateral renal nerves of these10canines for2s. The femoral artery bloodpressure, plasma noradrenalin in peripheral venous blood, sCr and BUNwere detected before modeling,1week after modeling,6days (n=5) and30days (n=5) after RSD. At the end of the experiment, bilateral renal arteriesand sympathetic nerves were observed pathologically. Similar procedureswithout ablation and establishing hypertension models were performed incontrol group (n=5). And the same experimental indicators were detected atthe same time as the ablation group.Results:1week after establishing hypertension models, the10caninesSBP were increased11.67%, SBP were increased12.72%, plasmanoradrenalin in peripheral venous blood were increased8.94%, p<0.05.After ablation, canines were with stable vital sign. On day6, BP and plasmanoradrenalin of5canines compared with1week after establishinghypertension models were significant decreased13.4%/9.59%, p<0.05;23.21%, p<0.05; On day30, another5canines BP and plasma noradrenalincompared with1week after establishing hypertension models weredecreased10.23%/11.29%, p<0.05;13.05%, p<0.05as well. Theexperimental indicators of control group had no significant difference. Therewere no significant differences of BUN and sCr levels of all canines and therenal function was normal. No significant injury was observed on the organsaround the bilateral renal arteries of the canines on day6and day30after ablation, but there histologic examination revealed the disruption of nervefibers and the necrosis of Schwann cell and neurons, while there were noabnormity changes in control group.Conclusion: MRI can provide clear soft tissue images. MRI-guidedHIFU ablation is accurate and feasible for renal sympathetic denervation incanines.