RADIOSOUND-HTN Suggests Ultrasound May Be Best for Renal Denervation

SAN DIEGO, CA—Renal denervation using ultrasound may be more effective than radiofrequency ablation for lowering blood pressure in patients with resistant hypertension, a preliminary head-to-head comparison of different techniques and technologies suggests.

When denervating only the main renal arteries, systolic daytime ambulatory blood pressure fell by an average of 6.5 mm Hg with radiofrequency ablation and 13.2 mm Hg with ultrasound ablation through 3 months (P = 0.042), Philipp Lurz, MD, PhD (Heart Center Leipzig, Germany), reported here at TCT 2018. Using radiofrequency to ablate the nerves in the main renal arteries, side branches, and accessories led to an average reduction of 8.3 mm Hg, which did not differ compared with the other two groups.

Similar patterns were seen for diastolic daytime ambulatory blood pressure, according to the findings, which were published simultaneously online in Circulation.

“Obviously, longer follow-up and large multicenter studies are needed to do head-to-head comparisons, especially to determine the long-term safety of these technologies,” Lurz said at a press conference, adding that “this pilot study precludes definite recommendations regarding the preferable renal denervation approach at present.”

RADIOSOUND-HTN

The study comes at a time when the field of renal denervation continues to move cautiously forward following the disappointment caused by the failure of the SYMPLICITY HTN-3 trial. Renewed research efforts have started to yield positive results in the form of three randomized, sham-controlled, pilot studies: SPYRAL HTN-OFF MED, SPYRAL HTN-ON MED, and RADIANCE-HTN SOLO. A fourth effort, REDUCE HTN: REINFORCE, could not duplicate that success.

All of those pilot studies had similar designs, but different renal denervation technologies were employed. The Symplicity Spyral catheter (Medtronic), which delivers radiofrequency energy through four electrodes, was used in the SPYRAL program, and the Paradise ultrasound catheter (ReCor Medical) was used in RADIANCE-HTN SOLO.

Lurz and colleagues set out to compare the two devices in the single-center RADIOSOUND-HTN trial, which randomized 120 patients with resistant hypertension to three groups:

• Denervation of the main renal arteries only with the Symplicity Spyral catheter
• Denervation of the main renal arteries, side branches, and accessories with the Symplicity Spyral catheter
• Denervation of the main renal arteries only with the Paradise catheter

At baseline, all patients had office blood pressures exceeding 160 mm Hg systolic or 90 mm Hg diastolic despite treatment with at least three antihypertensive drug classes, including a diuretic. Patients were taking an average of five medications and had a mean daytime ambulatory blood pressure of 153/86 mm Hg before renal denervation.

Across the three groups, the average reduction in daytime ambulatory blood pressure by 3 months was 9.5/6.3 mm Hg. Significant drops in systolic and diastolic pressure were seen in each group, although denervation with the Paradise catheter was associated with the largest decreases.

There was no difference across groups, however, in the proportion of patients who responded to treatment, defined as a reduction in systolic daytime blood pressure of at least 5 mm Hg. That figure was 66% when the Symplicity Spyral catheter was used in the main renal arteries only, 73% when that device was used additionally in the side branches and accessories, and 67% when the Paradise ultrasound catheter was used.

Looking at the patients who saw their blood pressure fall by at least 20 mm Hg revealed a potential advantage for denervation using ultrasound, with 29% of patients in that group reaching that threshold compared with 8% and 14% in the two radiofrequency groups.

Asked about the possible advantage for ultrasound denervation, Lurz said there are data from animal studies showing that ultrasound has a penetration depth of about 6 mm, which should be in the range to reach enough sympathetic nerves even if only the main renal arteries are targeted. It’s also possible that the ultrasound catheter provides a more complete circumferential ablation, he said, adding, however, that those explanations are hypothetical at this point.

In terms of safety, there were few events across the three groups, with one death deemed unrelated to the procedure, three vascular complications, and one hospitalization for hypertensive crisis.

Reason for Enthusiasm, but . . .

During a panel discussion at the press conference, Felix Mahfoud, MD (Saarland University Medical Center, Homburg/Saar, Germany), said he was pleased to see a late-breaking study on renal denervation because it indicates that “we’re back on track with this technology.”

Addressing that point, fellow panelist Deepak Bhatt, MD (Brigham and Women’s Hospital, Boston, MA), who was on the steering committee for SYMPLICITY HTN-3, said, “I think it’s back on track in terms of investigation, and I think there’s good reason to be enthusiastic and to continue to investigate.”

But Bhatt also provided a cautious message, stating that there is more to be learned about the technique and the right patients to treat.

“I think we still need large, adequately powered, sham-controlled trials before this technology should be approved and used in patients outside of carefully IRB-monitored studies,” he said. “I think we need to make sure that the newer technologies like ultrasound [and] more aggressive ablations such as with the Medtronic catheter are as safe as denervation seemed in SYMPLICITY HTN-3. There we demonstrated safety but lack of efficacy, so now we still need to, I think, redemonstrate safety and durability of the procedure over the long haul.”

A few years of data obtained from a sufficient number of patients is needed before renal denervation should be approved for clinical use, Bhatt continued.

“Otherwise, what’ll happen in the US is what’s happened in Europe and other parts of the world, where people are denervating without really any data supporting it,” he said. “It’s true, ultimately it does look like renal denervation has been resurrected, but if you recall there was a lot of hype there too initially, just like with the bioresorbable stents. . . . The problem with that sort of hype is it then leads to sort of overskepticism once the technology really is mature enough to be investigated. So bottom line: investigation, I’m really excited. Actual commercial use, premature.”