An animal study, published ahead of print in the Journal of the American College of Cardiology, indicates that renal denervation delivered through high-intensity focused ultrasound (HIFU) extracorpeal renal denervation may be an alternative approach to managing resistant hypertension as it is associated with blood pressure reduction without significant morbidity or mortality.
Qifeng Wang and Jing Huang, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China, and others reported in the JACC paper that while renal denervation was associated with “encouraging clinical outcomes” in patients with drug-resistant hypertension, intervention-related complications could occasionally occur. The authors commented: “In addition, vascular wall injury has been observed in a preclinical model and haemodynamic stenosis has been found in clinical case reports due to possibly related complications.” According to Wang et al, HIFU may be an alternative approach to the catheter-based, radiofrequency approach to renal denervation. They explained: “HIFU has been used non-invasively to ablate tissue by extracorporeally delivering focused acoustic energy. This technique is considered the ideal source of energy, especially for the ablation of deep solid tissue.”
In their study, they reviewed the use of a HIFU tumour therapeutic system (Model-JC200, Chongqing Haifu Technology) to ablate the bilateral renal nerves of healthy canines. Wang et al randomly assigned 18 dogs (of 23 overall) to receive renal denervation through HIFU and five dogs to receive a sham procedure. Using colour Doppler flowing imaging (CDFI) as a guide, the investigators placed the foci of the extracorporeal HIFU on the bilateral wall on the proximal, middle, and distal right renal artery, respectively. They wrote: “Therapeutic ablations (250 W x 2 seconds) were performed on each set of foci. A total of six emissions of acoustic power were delivered when every segment of the renal artery was visible on an ultrasonographic view. The therapeutic transducer was moved 2mm dorsally or ventrally to initiate the viewing of the next set of ablations.” Throughout the procedure, the abdominal wall of each canine was immersed in a therapeutic chamber filled with degassed water to provide acoustic coupling between the transducer and skin. The sham procedure was similar to the ablation procedure apart from acoustic energy being delivered.
Wang et al wrote: “On days six and 28 post-ablation, systolic blood pressure (12.3mmHg and 15.9mmHg, respectively; p” They added that both during and following the ablation procedure, the canines’ vital signs appeared normal and none of them died until they were sacrificed. Furthermore, gross and histological examinations did not reveal significant injuries along the acoustic path. Wang et al stated: “The targeted renal arteries were smooth and had an intact vascular wall and endothelium”
According to the authors, unlike the catheter-based strategy, the HIFU-mediated renal denervation technique can be performed “relatively independently” of anatomical variations in renal arteries. They stated: “This technique may be more suitable for certain conditions, such as bifurcated renal arteries and renal arteries that are smaller and shorter than normal” and added that there was some suggestion that the effect of HIFU-mediated renal denervation might be permanent as they said: “The myxoid change and shrinkage of the targeted renal nerve fibres were will present 28 days post-ablation.” Wang et al concluded: “This new strategy may provide an alternative approach to the clinical treatment of drug-resistant hypertension and other conditions associated with sympathetic overactivity.”
According to Huang, the head of the renal denervation project induced by ultrasound technique in the Second Affiliated Hospital of Chongqing Medical University, research into MRI-guided HIFU renal denervation is on going.