BP Reductions With Renal Denervation Durable to 30 Months: SYMPLICITY HTN-2

May 19, 2013

San Francisco, California — New data from the Symplicity HTN-2 study confirm the long-term efficacy of renal denervation in patients with resistant hypertension, with researchers reporting 30-month data showing that the novel catheter-based approach produces sustained blood pressure reductions in this group of patients.

Reporting on the Symplicity system (Medtronic) at the American Society of Hypertension (ASH) 2013 Scientific Sessions, lead investigator Dr Murray Esler (Baker IDI Heart and Diabetes Institute, Melbourne, Australia) said the results--despite being positive--still leave some unanswered questions when it comes to this emerging treatment for reducing blood pressure in resistant hypertension patients.

"I'll put this in a broader context," said Esler. "To use the words of Winston Churchill when he was rallying Britain during the war, 'This is but the end of the beginning.' There is a long way to go. In fact, to use the words of another politician, there are many known unknowns. Some of these will be answered soon with the Symplicity [HTN]-3 study, which is a little tighter designed than the Symplicity 2 study."

The Symplicity HTN-3 trial

Results of Symplicity HTN-2, a six-month study, were previously reported by heartwire . The ongoing Symplicity HTN-3 trial is a multicenter, 500-patient-plus, randomized, controlled trial testing the safety and effectiveness of the treatment in patients with uncontrolled hypertension (receiving at least three antihypertensive medications, one of which must be a diuretic). Led by Drs George Bakris (University of Chicago School of Medicine, IL) and Deepak Bhatt (VA Medical Center, Boston, MA), the trial will incorporate ambulatory blood-pressure monitoring in contrast to previous trials that relied on office blood-pressure measurements.

Commenting for heartwire on the 30-month results, ASH president-elect Dr Domenic Sica (Virginia Commonwealth University, Richmond, VA) said the renal-denervation field is changing so rapidly, with new and more novel catheters and the opportunity for more complete ablation, that long-term data from trials such as Symplicity HTN-2 will soon be dated. There are a number of companies entering into the fray, and five renal denervation catheter systems have already received CE Mark approval in Europe, including Symplicity. None are approved yet in the US.

"The field has potential," said Sica. "Many people have developed a love for the procedure and have been sufficiently enthusiastic about things that the more prudent physician, such as someone like myself, always steps back a little and lets it play out. It will never be as great as people say it's going to be, and it will never be as negative as the naysayers say. It'll find middle ground. It will require a prudent understanding of the field to determine what the middle ground is so that the procedure is used in the best patients."

Sustained reduction out to 30 months

The 30-month follow-up included data on 37 patients randomized to renal denervation. From baseline, systolic and diastolic blood pressure were reduced by 35 mmHg and 13 mmHg, respectively. Through 30 months, 84% of patients--including seven patients who crossed over from the comparator arm once the trial was completed--achieved a > 10 mmHg reduction in systolic blood pressure, and just over 70% of patients achieved a > 20 mmHg reduction in systolic blood pressure. These data are in line with the results observed at six, 12, and 24 months, said Esler.

In addition to the changes in blood pressure, there was a reduction in heart rate, down from 74 bpm at baseline to 69 bpm at 30 months. There was no reported increase in the dosing of blood-pressure medications post-procedure.

To heartwire , Sica cautioned that the study was small and there are always concerns about patients lost to follow-up. (In total, 49 patients were assessed at the six-month primary end point vs 37 assessed at 30 months.) Esler reminded the ASH audience that renal denervation is not a cure for resistant hypertension, but rather a complement to drug therapy. It is important for clinicians to remind patients undergoing the procedure about this important caveat because there are concerns some patients, after undergoing an invasive procedure, presume to be cured and stop their medication.

The emergence of renal denervation trials on the hypertension scene has inadvertently led to better treatment of resistant hypertension, added Esler. In attempting to identify patients who might qualify for treatment, physicians may make more disciplined efforts to get blood pressure under control, leading some patients to no longer qualify for the catheter-based procedure because of blood pressure improvements.

"It has brought this aspect of hypertension into focus," said Esler. "In the conduct of the trials, we are finding many patients we thought we would be denervating are not getting it because we're getting better at lowering their blood pressure with medication."

Need for procedural improvements

Despite the number of companies entering the field--Esler said there were 54 at last count--there is still a need for procedural improvements. Right now, the biggest problem is that it is impossible for clinicians to know if they have achieved successful denervation of the renal artery. "This is really a black hole for the interventionalist," he said. In addition, better selection of potential responders is needed.

Sica said that while it may not be possible to determine the patient best suited for the procedure based on demographics, it might be possible to identify a group of patients more receptive to renal denervation. For example, there are hypertensive patients who are medication intolerant, or those taking multiple medications but have bad side effects. "I think we can identify groupings of patients that we can go after that would be complementary to existing therapies without them being resistant hypertensives," he told heartwire .

Thumbs up from the ESC

In late April, as reported by heartwire , the European Society of Cardiology (ESC) issued a consensus statement on the use of catheter-based renal denervation for the treatment of high blood pressure. They said that the treatment can be considered a therapeutic option in patients with drug-resistant hypertension who cannot get to goal with a combination of lifestyle and pharmacologic therapy.

In Europe, Medtronic's Symplicity system has received CE Mark approval. Others include EnligHTN (St Jude Medical), used in the EnligHTN-1 study, Vessix V2 (Boston Scientific) used in REDUCE-HTN, OneShot (Covidien) used in RHAS, and Paradise (ReCor Medical) used in the REALISE study.

Esler reports research grants, honorarium, and serving on advisory boards for Medtronic. Sica is an advisor/consultant to Takeda, Novartis, Gambro, Medtronic, and CVRx. He receives research/grant support from Medtronic.

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