Renal Denervation Shows Sustained BP Improvements at 1 Year

Longer-term results from the Symplicity HTN-2 trial show sustained blood pressure reductions with renal denervation out to 1 year in patients with resistant hypertension. In addition, control patients who crossed over to treatment with the novel catheter-based system experienced BP lowering out to 6 months that was comparable to those who received immediate treatment, according to the study, published online December 17, 2012, ahead of print in Circulation.

In the main Symplicity HTN-2 trial, renal denervation via catheter-based radiofrequency (RF) ablation lowered blood pressure at 6 months in patients with treatment-resistant hypertension vs. controls. All patients had a baseline systolic blood pressure of 160 mm Hg or more despite taking at least 3 antihypertensive medications.

Consistent Results at 6 Months, 1 Year

For the updated results, initially presented March 25, 2012, at the annual American College of Cardiology (ACC)/i2 Scientific Session in Chicago, IL, researchers led by Murray Esler, MBBS, PhD, of the Baker IDI Heart and Diabetes Institute (Melbourne, Australia), looked at 1-year outcomes in the treatment arm and 6-month results in 35 patients who crossed over from the control arm to receive renal denervation.

At 1 year, the mean systolic blood pressure of the initial renal denervation group continued to be lower than baseline (-28.1 mm Hg; P < 0.0001), a reduction that was maintained from 6 months (-31.7 mm Hg; P = 0.16 vs. 1-year reduction). The crossover group also experienced a mean reduction at 6 months compared with baseline (-23.7 mm Hg; P < 0.001) that was similar to the reduction in the treatment group (P = 0.15).

Diastolic blood pressure at 6 and 12 months for the initial renal denervation group and at 6 months for the crossover group also was lower than baseline (P < 0.001 for all; table 1).

Table 1. Mean Office-based BP at Baseline, 6 and 12 Months after Renal Denervation

 

The majority of patients in the initial denervation group (83.7% at 6 months, 78.7% at 12 months) experienced drops of at least 10 mm Hg in systolic BP, while 62.9% of the crossover group experienced at least a 10 mm Hg reduction in systolic BP at 6 months.

Changes in medication use occurred in both groups. At 1 year, 27.9% of the initial renal denervation group had a decrease either in the number of medications or dose, while 18.6% had an increase. In the crossover group, 18.2% decreased their medication, while 15.2% had an increase.

In terms of safety issues, there was 1 right renal artery dissection in a crossover patient during guide catheter insertion for angiography prior to insertion of the Symplicity catheter (Ardian, Mountain View, CA). The lesion was stented without further complications and the patient was discharged following the denervation procedure without extended hospitalization. In another crossover patient, hospitalization following renal denervation was necessary because of a hypotensive episode requiring IV fluids and reduction in antihypertensive dosing. The patient was discharged with no further problems.

No significant changes in eGFR or cystatin C occurred in either group.

“This follow-up of the initial renal denervation cohort of patients confirms that the significant drop in mean blood pressure seen at 6 months post-renal denervation. . . is sustained at 12 months follow-up. . . with no significant difference between blood pressure reductions at 6 and 12 months,” the researchers conclude. They also note that prior to renal denervation treatment, the mean systolic BP of the crossover group had increased from 182.8 mm Hg to 190.0 mm Hg, suggesting “a natural tendency for blood pressure to increase in patients with treatment-resistant hypertension and suggest[ing] a potential cost in delaying renal denervation treatment.”

The Safety Debate

George L. Bakris, MD, of the University of Chicago Medical Center (Chicago, IL), called the results “very encouraging,” and noted that they confirm current experience with the procedure. In a telephone interview with TCTMD, he noted that the study helps alleviate concerns about potential side effects of renal denervation. “There really have not been the overwhelming initial concerns that were supposed to be there, they’ve just not been borne out,” he said. “There was a lot of concern about a very high incidence of renal artery stenosis from rebound hypertrophy. It hasn’t been true. In fact the complication rate in terms of the procedure itself really is directly proportional to what you would see from having a cardiac cath.”

In an e-mail communication with TCTMD, Michael Doumas, MD, of the Veteran Affairs Medical Center, George Washington University (Washington, DC), agreed that the results “add significant credit to the efficacy and safety of renal sympathetic denervation.” However, he added, “In my opinion, the current study is not sufficient to address concerns regarding long-term efficacy and safety,” for which longer-term data are needed. “Long-term concerns regarding efficacy are based on potential regeneration of renal sympathetic fibers or counter-balancing mechanisms that might attenuate the effects of [renal denervation],” Dr. Doumas explained. “Regarding safety, available results reveal an excellent safety profile which is further certified by this study. However, data for longer time periods are needed regarding renal artery anatomy and renal function.”

Dr. Bakris noted that even more important than the safety of  renal denervation is the concern that it will be viewed “as some panacea, that it’s going to cure everybody and it can be used as prophylaxis, and none of that’s true,” he said.

Instead, he explained, “this should be viewed as [appropriate for] the small subgroup of people that’s probably between 5% and 6% of all hypertensives who cannot be controlled by conventional medications. I don’t think there’s any question it’s going to have fairly significant utility in the subgroup of people that require 4, 5, 6 medications and are still not controlled.”

Study Details

For the renal denervation procedure, the Symplicity catheter (Ardian, Mountain View, CA) was advanced to the renal artery via femoral access and attached to a RF generator. Four to six discrete, low-power RF treatments were applied along the length of both main renal arteries in order to ablate the renal sympathetic nerves, because the nerves contribute to the development and perpetuation of hypertension.

 

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Source:
Esler MD, Krum H, Schlaich M, et al. Renal sympathetic denervation for treatment of drug-resistant hypertension: One year results from the Symplicity HTN-2 randomized controlled trial. Circulation. 2012:Epub ahead of print.

 

Disclosures:

• The funding source for the study was Medtronic Ardian.
• Dr. Esler reports receiving research support from Medtronic Ardian for the Symplicity HTN-2 trial.
• Dr. Bakris reports serving as the co-principal investigator of the Symplicity HTN-3 trial, sponsored by Medtronic.
• Dr. Doumas reports no relevant conflicts of interest.

 

Related Stories:

• Symplicity Works: Renal Denervation Reduces Resistant Hypertension
• Renal Denervation Reduced BP in Majority of Patients 
• Symplicity Itself: Endovascular RF Ablation Lowers Resistant Hypertension