Published: March 29, 2012

Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston and Dorothy Caputo, MA, RN, BC-ADM, Nurse Planner

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CHICAGO -- Renal denervation via radiofrequency ablation to treat refractory hypertension resulted in safe, significant, and sustained blood pressure reduction, two clinical trials showed.

Three-year results of the nonrandomized SYMPLICITY HTN-1 study are as good as the 2- and 1-year results, essentially maintaining a drop in office blood pressure of -33/-19 mm Hg compared with baseline, reported Paul A. Sobotka, MD, from Ohio State University in Columbus.

At baseline, more than 90% of patients had systolic blood pressure readings greater than 160 mm Hg, but at one year, more than 90% had dropped their pressure to below 159 mm Hg, said Sobotka at the American College of Cardiology meeting here.

One-year results were reported at the 2009 Transcatheter Cardiovascular Therapeutics meeting.

Renal denervation involves the use of a radiofrequency catheter to create lesions in renal arteries that disrupt the sympathetic nerve pathways that lie within the renal artery wall and lead into and out of the kidneys. The procedure, which takes about 40 minutes to complete, has been shown to reduce blood pressure in those with resistant hypertension.

Sobotka said that hypertension is the single largest contributor to death worldwide. "Every 20/10 mm Hg increase in blood pressure correlates with a doubling of 10-year cardiovascular mortality," he said.

SIMPLICITY HTN-1 is a multicenter trial encompassing 19 sites in Australia, Europe, and the U.S. The initial cohort (first-in-man study) comprised 45 patients with resistant hypertension, defined as systolic blood pressure greater than 160 mm Hg, the use of three or more anti-hypertensive medications, and an estimated glomerular filtration rate of 45 mL/minute or greater.

Researchers expanded the number of patients to 153, and the current study examined 3-year results. The average age of patients was 57 and 39% were women. Most patients were white.

Not everyone initially responds favorably to renal denervation, Sobotka said. However, this study showed that the percentage of responders increased over time. At 1 month, 69% of 143 patients responded; at 12 months, it was 79% of 130 patients; at 2 years, it was 90% of 59 patients; and at 3 years, 100% of 24 patients followed for 36 months responded.

Researchers arbitrarily chose a cutoff point of a reduction of ?10 mm Hg in systolic blood pressure to define responders.

"Although this marker was chosen arbitrarily, it may help to identify those who will be better responders to the therapy," Sobotka said.

Of the initial nonresponders (defined as a reduction of less than 10 mm Hg in systolic blood pressure), all eight patients who were followed for 3 years eventually became responders.

Whether patients were younger or older than 65 did not affect the positive blood pressure changes following treatment, Sobotka said.

The positive reductions in blood pressure remained when researchers separated out diabetic patients, as well as those with renal dysfunction.

Sobotka reported that the procedure appears safe, with relatively few complications, including no deaths related to the procedure.

"The magnitude of clinical response is significant and sustained through 3 years," he concluded. "Also, no response at 6 months in blood pressure reduction does not predict failure at 12 months."

Randomized Study

In the randomized controlled SYMPLICITY HTN-2 trial, the benefits of renal denervation were sustained out to 1 year, reported principal investigator Murray D. Esler, MD, PhD, associate director of the Baker IDI Heart and Diabetes Institute of Melbourne, Australia.

The 6-months results were reported at the 2010 American Heart Association meeting.

SYMPLICITY HTN-2 encompasses 24 centers in Europe, Australia, and New Zealand. A total of 106 patients were randomized to renal denervation or standard treatment.

At baseline both arms had similarly high blood pressure (178/98 mm Hg), "despite receiving an average daily regimen of five antihypertensive medications," Esler said.

Of the 47 patients followed for 1 year, those in the denervation group sustained a significant drop in blood pressure (-28/-10 mm Hg, P<0.001) similar to the reduction seen at 6 months.

Thirty-five patients in the control group crossed-over to renal denervation at the 6-month follow-up. They also had a reduction in blood pressure at 6 months post procedure that was similar to the treatment arm (-24/-8 mm Hg).

There were no significant safety issues associated with renal denervation, including no decline in kidney function or late vascular complications, Esler reported.

At 6 and 12 months, 21% and 28%, respectively, of the renal denervation patients had a decrease in medication. Also, 12% and 19%, respectively, had an increase in their medication.

For the crossover group, the rates of decreases and increases in medication at 6 months were 18% and 15%, respectively.

Esler concluded that renal denervation can provide long-term safety and efficacy for patients with resistant hypertension.

The Symplicity renal denervation system, which was used in the trial, is not approved by the FDA for use in the U.S.

Funding for the SYMPLICITY studies was provided by Ardian.

Sobotka disclosed that he is an employee of Medtronic. Esler disclosed that he received funding from Medtronic and Ardian.

Primary source:American College of Cardiology
Source reference:
Esler M, et al "Renal sympathetic denervation for treatment of resistant hypertension: One-year results from the Symplicity HTN-2 randomized controlled trial" ACC 2012.

Additional source: American College of Cardiology
Source reference:
Sobotka PA, et al "Symplicity HTN-1: Long-term follow-up of catheter-based renal sympathetic denervation for resistant hypertension confirms durable blood pressure reduction" ACC 2012.

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