Early Study Shows Positive Clinical Results with Novel Renal Denervation Device

LOS ANGELES, CA—Three-fourths of patients with resistant hypertension show a positive blood pressure (BP) response to treatment with a novel multi-electrode renal denervation catheter, according to 6-month, first-in-man results presented November 5, 2012, at the American Heart Association Scientific Sessions.

For the EnligHTN I trial, Vasilios Papademetriou, MD, of Hippokration General Hospital of Athens (Athens, Greece), and colleagues studied 46 patients with resistant hypertension (176/96 mm Hg) taking an average of 4.1 antihypertensive medications. Patients were treated with a multi-electrode catheter ablation system (EnligHTN, St. Jude Medical, St. Paul, MN), which differs from the single-tip electrode ablation catheter that has been used in trials such as Symplicity HTN 1 and 2 to achieve sympathetic fiber interruption through the renal artery wall.

 The EnligHTN catheter is 8-Fr compatible and features 4 electrodes on an expandable basket. Two rounds of ablation—the second after slight pull-back of the catheter—are performed at 90 seconds per round, with electrodes reaching a temperature of 75 degrees C. The goal is to create a predictable pattern of transmural lesions circumferentially around the renal artery, causing renal fiber interruption without scarring. The EnligHTN system is CE marked in Europe and has not been approved in the United States.

 Efficacy Sustained at 6 Months

 At 6 months (3-month results were presented at the Transcatheter Cardiovascular Therapeutics symposium in Miami, FL), there was no clinically significant change in renal function after treatment. In addition, the primary endpoint of office BP reduction continued to maintain the positive results that were achieved at 1 and 3 months, as did 24-hour ambulatory BP (table 1).

 Table 1. Blood Pressure Reductions from Baseline (Systolic/Diastolic)

All P values are < 0.0001 except 24-hour diastolic at 1 month (P = 0.003) and 3 months (P = 0.0002).

Three-fourths (76%) of the patients (n = 34) were classified as “responders,” meaning they achieved more than a 10 mm Hg reduction in systolic BP from baseline. Only 6.7% had systolic BP above 180 mm Hg, and two-thirds of patients experienced a great enough BP reduction by 6 months to move to a lower stage of hypertension classification/treatment. In addition, one-third (33.3%) no longer met the classification for hypertension at all (< 140 mm Hg systolic).

There were no serious periprocedural adverse events, although there were some nonserious adverse events including vasospasm, puncture site hematoma, low back pain, and hypotensive episodes. Serious device/procedural events included worsening of pre-existing proteinuria (n = 1), symptomatic hypotension (n = 1), and worsening of pre-existing renal stenosis (n = 1).

“The procedure is safe, it can be done without any major complications,” Dr. Papademetriou said. “It results in a rapid reduction in blood pressure. We noticed a reduction of 28/10 mm Hg at 1 month and even earlier and this is sustained up to 6 months. We can therefore conclude that the EnligHTN system delivers a promising therapy for the treatment of patients with drug-resistant hypertension.”

Similar to Symplicity?

Commenting on the results, Robert M. Carey, MD, of the University of Virginia Health System (Charlottesville, VA), noted how the 6-month reduction in BP with the EnligHTN system (26/10 mm Hg) was similar to that achieved over the same time period in Symplicity 1 (22/11 mm Hg reduction) and Symplicity 2 (33/11 mm Hg reduction). A major difference was the lack of a control group in EnligHTN I, he noted.

He cautioned, though, that “the results from available clinical trials cannot simply be extrapolated to less severe forms or secondary forms of hypertension. We need to engage in blinded, controlled efficacy studies in order to make that jump.”

Dr. Carey estimated the frequency of true resistant hypertension as being about 14%, noting that of these patients, recent research suggests that about 58% can achieve BP goals through sequential nephron blockade with different types of diuretics acting at different nephron segments. “So it comes down to an issue of cost and side effects and efficacy of oral therapy vs. renal denervation blockade,” he said.

A key knowledge gap to address in future studies is whether renal re-inervation occurs long term and if so whether it cancels the observed reduction in BP. “So far, we would predict from the available data that the reduction in blood pressure would probably not be canceled,” Dr. Carey said. “But these studies need to continue, and we need to accumulate long-term clinical outcomes data as well.”

Source:

Papademetriou V. EnligHTN I, first-in-human multicenter study of a multi-electrode renal denervation catheter in patients with drug-resistant hypertension. Presented at: American Heart Association Scientific Sessions; November 5, 2012; Los Angeles, CA.

Disclosures:

• Dr. Papademetriou reports serving on the speaker’s bureau for Astra Zeneca and receiving research grants from and serving as a consultant/advisory board member for St. Jude Medical.
• Dr. Carey reports no relevant conflicts of interest.

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