Evidence continues to point favorably to the efficacy and safety of renal denervation as a treatment for resistant hypertensive patients. Findings from Symplicity HTN-2, published Dec. 18 in Circulation, showed benefits persisted at one-year while control patients who crossed over to renal denervation after the six-month primary endpoint was met experienced drops in blood pressure similar to the treatment group.

Three-year results for Symplicity HTN-1 gave renal denervation a thumbs up for longer-term efficacy and safety, but the trial was not randomized. Symplicity HTN-2, an ongoing randomized study, enrolled 106 patients with drug-resistant hypertension with systolic blood pressure of 160 mm Hg or higher who were on at least three medications for hypertension. Forty-nine patients underwent a catheter-based renal denervation procedure (Symplicity, Medtronic) and 51 received no treatment with medication unchanged. At six-month follow-up, 83.7 percent in the treatment group experienced a reduction of office-based systolic blood pressure of at least 10 mm Hg.

In this study, Murray D. Esler, MBBS, PhD, of the Baker IDI Heart and Diabetes Institute in Melbourne, Australia, and colleagues reported one-year results for the treatment group and six-month results for the 35 patients in the control group who elected to undergo the procedure after the six-month primary endpoint was met.

At 12 months, mean systolic blood pressure in the initial renal denervation group remained significantly lower than at baseline, with a change of minus 28.1 mm Hg; at six months, the mean was minus 31.7 mm Hg. The percentage of patients who experienced a reduction of office-based systolic blood pressure of at least 10 mm Hg dipped slightly, to 78.7 percent.

The cross-over group results paralleled findings at six months for the treatment group, with mean office-based systolic blood pressure dropping from 190 mm Hg at baseline to 166.3 mm Hg at six months and 62.9 percent experiencing a reduction of office-based systolic blood pressure of at least 10 mm HG.

The six-month cross-over results provide some additional safety data, including:

• One right renal artery dissection during guide catheter insertion for angiography, which was stented without further complications; and
• One hospitalization due to a hypotensive episode needing intravenous fluids and reduction in antihypertensive dosing. The patient was discharged with no further problems.

“This follow-up of the initial renal denervation cohort of patients confirms that the significant drop in mean blood pressure seen at six months post-renal denervation (minus 32 mm Hg) is sustained at 12 months follow-up (minus 28 mm Hg) with no significant difference between blood pressure reductions at six and 12 months,” Esler and colleagues wrote. “These results are consistent with the longer term responses observed in the Symplicity HTN-1 trial and an associated renal denervation registry which reported substantial drops in SBP [systolic blood pressure] at 12 (minus 23 mm Hg) and 24 months (minus 32 mm Hg) for 153 patients with resistant hypertension.”

The researchers noted that at six months and prior to renal denervation, the mean systolic blood pressure in the control group had increased from 182.8 mm Hg to 190 mm Hg. “This increase in blood pressure while on a stable antihypertensive regimen may represent a natural tendency for blood pressure to increase in patients with treatment-resistant hypertension and suggests a potential cost in delaying renal denervation treatment,” they wrote. “However, these patients represent a subset of the original control group; removal of subjects who chose not to undergo renal denervation or no longer had a SBP less than 160 mm Hg introduces selection bias that may account for the differences in pre-procedure blood pressure and renal function.”

Renal function measures remained unchanged at six and 12 months after renal denervation, and there were no reports of persistent symptomatic hypotension. Those findings add to evidence suggesting the procedure is safe, they wrote.

Symplicity HTN-2 did not use 24-hour blood pressure monitoring, and patients and staff were not blinded to the intervention. The authors wrote that the randomized Symplicity HTN-3 trial has been designed to overcome those shortcomings.

Medtronic Ardian funded the study.

For more information on renal denervation as a potential treatment of hypertension, heart failure and atrial fibrillation, please read “Newest Frontier in Cardiac Care: Kidneys” in the winter issue of Cardiovascular Business.