SYMPLICITY-FLEX: Renal Denervation Misses in Mildly Hypertensive Patients

September 16, 2014

WASHINGTON, DC — A very small study in patients with mildly elevated blood pressure has shown that renal denervation failed to lower systolic blood pressure compared with patients undergoing a sham control procedure.

Presenting the data from SYMPLICITY-FLEX at TCT 2014 , Dr Steffen Desch (University of Leipzig Heart Center, Germany) reported that patients randomized to renal denervation had a 7.0-mm-Hg reduction in 24-hour ambulatory blood pressure at six months, whereas the sham control arm patients had a 3.5-mm-Hg reduction. This difference was not statistically significant.

When investigators performed a per-protocol analysis, excluding two patients who had incomplete ablations, one patient who did not undergo a sham procedure, and another who should not have been randomized because of severe renal-artery stenosis, there was a statistically significant 4.8-mm-Hg greater reduction in systolic blood pressure in the renal-denervation patients compared with the sham arm.

Still, Desch told heartwire that he no longer performs renal-denervation procedures. He said the last ablation he performed was in January 2014, just before Medtronic, the sponsor of the SYMPLICITY HTN-3 study, announced the trial missed its primary end point. "The press release came out in January, and I was just a little hesitant to go on," said Desch.

The SYMPLICITY HTN-3 study was later presented at the American College of Cardiology 2014 Scientific Sessions in March and reported by heartwire . Six months following renal denervation, the SYMPLICITY HTN-3 investigators reported a mean change in systolic blood pressure of 14.13 mm Hg in the renal-denervation arm and 11.74 mm Hg in the sham control arm, a difference of 2.39 mm Hg that was not statistically significant. Similarly, there was no significant reduction in the 24-hour ambulatory blood-pressure measurement.

Speaking with the media, Desch said the FLEX study differed from HTN-3 in that they randomized patients with mildly elevated systolic blood pressure. The patients all had resistant hypertension, and 40% were treated with five or more antihypertensive agents, but the baseline systolic blood pressure in FLEX was approximately 144 mm Hg. Comparatively, the baseline systolic blood pressure in SYMPLICITY HTN-3 was 163 mm Hg. FLEX investigators measured only 24-hour ambulatory blood pressure.

"This is a whole different patient population as compared with SYMPLICITY HTN-3," said Desch.

The study was small, with just 35 patients in the renal-denervation arm and 36 in the sham control arm. As noted, the study missed its primary end point at six months, with investigators observing no difference in the mean change in 24-hour systolic blood pressure from baseline to six months between the two groups.

Despite the negative results, Desch still believes renal denervation might pan out, especially as the technology improves. Newer "spiral" catheters might be able to achieve better technical success by allowing physicians to perform circumferential ablation of the renal arteries, he noted.

Dr Horst Sievert (Cardiovascular Center, Frankfurt, Germany), who was not affiliated with the study but is a member of the European Society of Cardiology writing committee that issued a consensus statement on renal denervation in April 2013, said he still performs renal denervation in resistant-hypertension patients at his center.

Commenting on the SYMPLICITY-FLEX study, Sievert took an optimistic view of the data, saying investigators had "extraordinary results" given the patient population. The intention-to-treat and per-protocol reductions in systolic blood pressure were 7.0 mm Hg and 8.3 mm Hg, respectively, and this reduction was sizable for patients with mild hypertension. "You couldn't expect more than what was achieved," he said.

Desch reports no conflicts of interest. Sievert reports consulting fees and honoraria from Abbott, Access Closure, AGA, Angiomed, Aptus, Atrium, Avinger, Bard, Biosense Webster, Boston Scientific, Bridgepoint, Carag, Cardiac Dimensions, CardioKinetix, CardioMEMS, Cardiox, Celonova, Coherex, Contego, Covidien, CSI, CVRx, EndoCross, ev3, FlowCardia, Gardia, Gore, GTIMD Medical, Guided Delivery Systems, Hemoteq, InSeal Medical, InspireMD, Lumen Biomedical, HLT, Lifetech, Lutonix, Maya Medical, Medtronic, NDC, Occlutech, Osprey, Ostial, PendraCare, pfm Medical, Recor, ResMed, Rox Medical, SentreHeart, Spectranetics, SquareOne, Svelte Medical Systems, Trireme, Trivascular, Vascular Dynamics, Venus Medical, Veryan, and Vessix.

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