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SAN DIEGO -- Ultrasound ablation came out on top in a head-to-head comparison of renal denervation techniques, investigators found from the RADIOSOUND-HTN trial.

Hypertensive patients showed the greatest average drop in daytime ambulatory blood pressure (BP) 3 months after they had been randomized to ultrasound ablation of the main renal artery alone (versus radiofrequency ablation of the main renal artery with or without branch arteries):

• Systolic BP: -13.2 mm Hg (versus -8.3 mm Hg versus -6.5 mm Hg, P=0.042 for ultrasound versus radiofrequency main-artery ablation)
• Diastolic BP: -7.6 mm Hg (versus -6.1 mm Hg versus -3.2 mm Hg, P=0.002)

On an individual level, however, the actual proportion of patients that had BP drop by at least 5 mm Hg did not differ among treatment groups (67% versus 73% versus 66%), according to Philipp Lurz, MD, PhD, of Germany's Heart Center Leipzig at University of Leipzig, during his presentation at the (TCT) annual meeting.

RADIOSOUND-HTN was simultaneously published online in .

"The magnitude of treatment effect might not necessarily go along with improved frequency of BP response. This should be considered when analyzing and interpreting effects of renal denervation in future trials," Lurz and colleagues wrote. In principal, they said, non-responders either have anatomy that hinders the completeness of denervation -- or don't have elevated sympathetic nervous activity as the main contributor to their hypertension.

The investigators suggested that future trials "focus on identifying these patients to avoid futile renal denervation procedures but also on defining specific anatomic predictors associated with a more effective renal denervation procedure."

In RADIOSOUND-HTN, radiofrequency ablations were handled with the Symplicity spiral catheter; ultrasound ablations were performed with the Paradise catheter.

Safety data showed few events across groups:

• Radiofrequency ablation of the main artery only (n=39): one death (not related to procedure) and one vascular complication
• Radiofrequency ablation of main artery plus branches (n=39): one vascular complication and one hospitalization for hypertensive crisis
• Ultrasound ablation of main artery alone (n=42): one vascular complication

This makes the safety profile of these denervation techniques "acceptable," Lurz said, noting that there was no renal artery stenosis in any patient.

The single-center trial had 120 patients randomized (of which 117 completed 3-month follow-up). Participants were patients with resistant hypertension who had been treated with at least three drug classes at 50% or greater maximum dosage -- this they kept constant unless there was an indication for a change in medication.

Baseline 24-hour ambulatory BP was 150/84 mm Hg and was similar between groups.

"Longer follow up and larger, multi-center studies investigating different renal denervation technologies and techniques are needed to determine long term safety as well as efficacy," Lurz told the audience.

Even so, the new data "indicate we are back on track for this technology," said Felix Mahfoud, MD, of Saarland University Medical Center in Germany.

"We now have three sham-controlled trials indicating that the technology is working and there are two pivotal studies ongoing in the U.S., Australia, Europe, and Japan," he said in a TCT press conference. "Lastly, I think it's interesting that we are now at the stage of development of renal denervation where head-to-head trials are coming."

"I think it's back on track in terms of investigation. There's good reason to be enthusiastic and continue to investigate" agreed fellow panelist Deepak Bhatt, MD, MPH, of Brigham and Women's Hospital in Boston.

However, "I think we need to learn more about the technique, learn about the patients. We still need large adequately-powered sham-controlled trials before the technology should be approved," Bhatt said. "We need to make sure the newer technology of ultrasound is as safe as radiofrequency was in SYMPLICITY. We need to re-demonstrate safety."

Otherwise the disappointment after the hype will only lead to overskepticism once the technology is mature enough to be investigated, Bhatt cautioned.

RADIOSOUND-HTN had the limitation of being "neither designed nor sufficiently powered to compare nocturnal BP between the groups," the investigators acknowledged. In addition, BP was assessed only at 3 months, whereas a more pronounced effect may be expected at 6 months, given the data from SPYRAL-HTN-ON-MED and SYMPLICITY-HTN-2, they said.

Another caveat was that the trial only included patients with larger renal arteries because of the assumption that sympathetic fibers are farther from the lumen and therefore more relevant to radiofrequency ablation and its high penetration depth.

"Therefore, results might have differed in a cohort of patients with smaller renal artery diameters," Lurz's group cautioned.

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