SAN DIEGO – Denervation of the main renal arteries with ultrasound is more effective than radiofrequency (RF) ablation at lowering blood pressure in patients with resistant hypertension, according to a single-center, randomized trial from Germany.
M. Alexander Otto/MDedge News
Dr. Philipp Lurz
Dubbed RADIOSOUND–HTN, it was the first time the two emerging technologies have been pitted against each other. At 3-month follow-up, the 42 patients randomized to ultrasound ablation with the Paradise catheter (ReCor Medical) had a mean systolic daytime blood pressure reduction of 13.2 mm Hg on ambulatory monitoring, vs. 6.5 mm Hg among 39 patients randomized to RF ablation with Medtronic’s Symplicity Spyral catheter (P = .043).
Meanwhile, 39 patients randomized to both main artery and side branch ablation with the Spyral had a mean reduction of 8.3 mm Hg, slightly better than RF ablation of the main renal arteries alone, but the difference was not statistically significant, and “no definite conclusion on the value of an additional side branch ablation can be drawn,” said senior investigator Philipp Lurz , MD, PhD, a cardiologist at the University of Leipzig, Germany, and his colleagues (Circulation. 2018 Sep 25. doi: 10.1161/circulationaha.118.037654).
Denervation was probably more complete with the Paradise catheter, which might explain the results. Ultrasound energy penetrates about 6-7 mm from the lumen, reaching up to 90% of sympathetic nerve fibers, while RF energy penetrates 3-4 mm; indeed, the idea of going into the branches with RF ablation is because nerve fibers are closer to the lumen surface, Dr. Lurz said at the Transcatheter Cardiovascular Therapeutics (TCT) annual meeting, where he presented the study, which was simultaneously published in Circulation.
Also, the Paradise catheter – an endovascular balloon device inflated to fit the lumen – delivers fully circumferential, ringlike ablations with each application, while the Spyral catheter delivers four ablations simultaneously in a spiral pattern, and requires more ablations to create a similar effect, according to Dr. Lurz.
About two-thirds of patients in all three arms responded to treatment, meaning at least a 5 mm Hg drop in systolic blood pressure. Among the nonresponders, it’s possible that their hypertension wasn’t caused by sympathetic overdrive. “Future trials should focus on identifying these patients to avoid futile” procedures, and define “specific anatomic predictors associated with a more effective” renal denervation, Dr. Lurz and his team said in their study report.
The researchers noted that “the present study included patients with larger renal arteries” – at least one renal artery 5.5 mm or greater in diameter – “based on the assumption that sympathetic fibers are in greater distance from the lumen than in smaller arteries, and therefore ... higher penetration depth would be more relevant ... Results might have differed in a cohort of patients with smaller renal artery diameters.”
Both Paradise and Spyral are in pivotal trials for Food and Drug Administration approval.
The subjects were an average of 64 years. The majority were men, and there were no significant differences in baseline characteristics between the arms. The mean baseline daytime blood pressure was 153/86 mm Hg despite treatment with three or more classes of antihypertensives dosed to at least 50% of their maximum. There was no drug testing to confirm patients were taking their medications, but their general practitioners vouched for their adherence.
One patient in the ultrasound arm group developed a pseudoaneurysm treated successfully by compression. One of the RF subjects developed a postprocedural intracapsular and retroperitoneal hematoma that resolved spontaneously. No renal vascular complications or stenoses were detected at follow-up.
There was no industry funding for the work. Dr. Lurz is a speaker and consultant for both ReCor Medical and Medtronic.