News from the FDA/CDC

FDA panel split on efficacy of Spyral renal denervation system


The Food and Drug Administration’s Circulatory System Devices Panel unanimously agreed that the Symplicity Spyral Renal Denervation System (Medtronic) is safe, but the panel was split on its efficacy and whether the benefits outweighed the risks associated with its use.

The panel voted 13-0, with 0 abstentions, that it is safe, but 7-6, with 0 abstentions, that it is effective. It voted 6-6, with 1 abstention, that the benefits outweigh the risk. The moderator’s tiebreaker vote went against the benefit-risk profile, for a final vote of 6 yes, 7 no, and 1 abstention.

The Symplicity Spyral system provides a catheter-based approach to denervate the renal arteries using radiofrequency energy. The proposed indication is for reduction of blood pressure in patients with uncontrolled hypertension despite their use of antihypertensive medications, or in patients who cannot tolerate antihypertensive medications.

The Spyral device received breakthrough device designation in March 2020. The FDA determined that the device met the criteria for inclusion in the program because it was a novel technology and had the potential to provide more effective treatment for patients with resistant or uncontrolled hypertension.

Medtronic presented data from two studies, the SPYRAL HTN-OFF and SPYRAL HTN-ON randomized trials.

HTN-OFF enrolled patients with hypertension whose medications could be discontinued at the start of the trial. The primary effectiveness endpoint was the mean difference in the baseline adjusted 24-hour ambulatory systolic blood pressure (ASBP) from baseline to 3 months post renal denervation or sham procedure. The study showed a statistically significant reduction of 3.9 mm Hg ASBP in patients who received the device compared with sham control patients.

HTN-ON evaluated patients with uncontrolled hypertension who continued taking their blood pressure medications during treatment with either the Spyral renal denervation device or a sham device. The primary endpoint was the mean difference in the baseline adjusted 24 hour ambulatory systolic blood pressure at 6 months. The study showed a nonsignificant 24-hour 0.03–mm Hg reduction in ambulatory systolic blood pressure in active-treatment patients compared with sham control patients.

Many on the panel agreed that the device was safe and effective. Randall Starling, MD, professor of medicine in the Heart, Vascular, and Thoracic Institute at Cleveland Clinic, said that he was comfortable with the data presented by Medtronic and that his affirmative vote reflected his recognition that hypertension is not effectively treated with current medications and that another tool in the armamentarium to treat patients is needed.

Matthew Corriere, MD, Frankel Professor of Cardiovascular Surgery at the University of Michigan, Ann Arbor, abstained from voting on whether the benefits of the system outweighed its risks. “I think there is potential benefit, but we don’t know which patients are most likely to have a benefit that outweighs any risks. More selective indications for this product could potentially tip the balance of the benefit outweighing the risks,” he said.

Robert Yeh, MD, director, Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Boston, said he believed that the device was safe and effective and that its use resulted in a favorable risk-benefit ratio for patients. He pointed to the wide variability in effectiveness across the patient population and suggested that as the device becomes more widely used, experience will show which patients will benefit the most from its use.

Keith Allen, MD, director of surgical research at St. Luke’s Hospital of Kansas City, Kansas City, Mo., said the data presented by Medtronic reassured him that the device was safe, but he said he remained unconvinced that the device was effective. “I think that, while this is a safe procedure, the efficacy was mild at best, and that was only at 3 months,” he said.

Other panel members agreed.

“Yes as to safety, but no as to effectiveness,” said Mark Lockhart, MD, professor, department of radiology, University of Alabama, Birmingham. “There is too much uncertainty about there actually being a real benefit to outweigh even a small risk of an invasive procedure,” he said.

One of the statisticians on the panel, Benjamin Saville, PhD, director and senior statistical scientist, Berry Consultants, Austin, Texas, said he did not feel that effectiveness was adequately demonstrated in the trial data presented by Medtronic.

He agreed there is a small but potentially clinically meaningful benefit but voted no because he did not think benefit was demonstrated for those patients in the proposed indication. “For me, I think I would need additional randomized data to convince me that the benefits outweigh the risks.”

Julia Lewis, MD, professor of medicine at Vanderbilt University, Nashville, Tenn., voted against endorsing the device for efficacy. “We have one study that is negative and one that is minimally positive,” and there is no reason to think one of those results is more valid than the other, she said.

“So as far as I’m concerned, we still don’t know the efficacy of this, and if it gets on the market, the anecdotal, small sample size of each individual physician using this intervention will not allow them to select out the patients that will benefit from those who won’t benefit, and to not have a definitive study that better defines that it is efficacious and in whom is actually a disservice to the public,” she concluded.

After the panel meeting, Medtronic issued a statement on the result.

“We appreciate the robust conversation that occurred prior to the vote,” Jason Weidman, senior vice-president of the coronary and renal denervation business at Medtronic, said in the statement. “We will continue to collaborate with the FDA on bringing a new option to the millions of people living with high blood pressure.”

The lead investigator of the SPYRAL HTN-ON MED trial, David Kandzari, MD, chief at Piedmont Heart Institute and Cardiovascular Services, added, “The totality of the evidence demonstrated that there is a benefit with the SPYRAL RDN catheter, and there is no question about the safety of the procedure.”

A version of this article first appeared on

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