Noninvasive Renal Sympathetic Denervation By High-intensity Focused Ultrasound (HIFU) In Dogs

Backgrounds and Objective：Although catheter-based renal sympathetic denevation (RSD) byradiofrequency ablation which decreased the activities ofsympathetic nerve has shown significant results in hypertensiontreatment, associated complications and impairments to renal artery(RA) promoted search for alternative energy sources and means. Thisstudy addresses feasibility and safety of extracorporeal noninvasiveRSD using High-Intensity Focused Ultrasound (HIFU) application.Methods：Fifteen healthy adult mongrel dogs were anesthetized with3%pentobarbital sodium (30mg/Kg) intraperitoneally,8.8%Sodiumsulphide solution for depilation on area from bilateral chest midpieceto anterior superior iliac spine,75%alcohol for lipid-removal,electro-extractor as negative pressure drainage for skindegassing.Then,the subject was left side-lying on treatmenttable(JC200High-Intensity Focused Ultrasound System on TumorTreatment, Chongqing Haifu Technology Co.Ltd) with therapeutic area completely soaking in de-aerated water.250W×2sec was selectedas the energy in subsequent studies. Determine the clearest and entireimage of red signals (renal artery) long axis’s cross-section as thestandard section guilded by2-D ultrasound and Color Doppler flowimaging,which need modulate the opposite position of transducer andanimal. Along with red signals long axis, renal ateries were dividedinto3segments artificially,namely abdominal aorta(a), middle(b) andrenal hilum(c).Focus was placed on the bilateral edges of Eachsegment, with totally6ablated points in single layer.Afterthat, thetransducer was parallel shifted to spinal and ventral lateralrespectively(intermediate layer length2mm).Ablation was performedin the present of flow signal segments until the signals disappeared.Results：It was gained4-6ablation layers at one-side and costed42±9minutes from location to ablation.Both blood pressure andnoradrenaline concentration are decreased remarkably six days afterthe operation,-9/-21mmHg（P<0.05）and-361.4pg/ml（P=0.00）respectively. Serum natremia decreased from150.3±2.1mmol/L to146.2±3.8mmol/L（P=0.00）. Biochemical renal functions are nochange.Ablation lesions in shape of punctum and lineation can beobserved on the surface of adipose tissue around the renal vesselgrossly. Nerve fiber vacuolar degeneration, pyknosis、dark stained as well as degeneration and disappear of nucleus, swelling neuronal cellin motor ganglion of injured point, and vanished Nissl body can beobserved microscopically. There is no other postoperative tissularinjury.Conclusions：With ultrasound image to precisely orientate and locate, HIFUapplication realizes safe and effective RSD in destruction of renalnerve fibers structurally and functionally, which enable it anotherinnovation in noninvasive RSD.