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NEW ORLEANS -- It's "rare" that hypertensive patients undergoing radiofrequency renal denervation end up getting another renal intervention, researchers said here, and when it does happen it usually comes quickly.

A meta-analysis comprising trial and registry data for the Symplicity Flex and Symplicity Spyral catheters found that renal artery stenosis or dissection occurred in 0.45% of patients within about 2 years post-procedure, according to a group led by Raymond Townsend, MD, of the University of Pennsylvania in Philadelphia.

Renal artery stenting was required in 0.41% of the group overall for an annual incidence of 0.20% per year, Townsend's team showed in a poster exhibited at the American Heart Association's .

"Renal artery re-intervention following renal denervation with the most commonly applied radiofrequency renal denervation system is rare," they concluded. Their meta-analysis included 5,769 patients with 10,249 patient-years of follow-up.

Median time from renal denervation to any subsequent renal intervention was 6 months; 79% of events occurred in 1 year.

Study authors noted no stent implants so far among those who underwent renal denervation with the Symplicity Spyral in particular. This is the newer system of the two from Medtronic, featuring more electrodes to deliver up to four simultaneous radiofrequency ablations in a helical pattern.

When looking at 14 trials reporting prospective follow-up imaging data, Townsend and colleagues found just one new significant stenosis in 511 people (0.20%).

In addition, most cases of severe renal artery stenosis were identified after recurrent hypertension, according to 11 published case reports.

Yet only time and more patients will tell if renal denervation is truly safe: Symplicity Spyral is under investigation in the SPYRAL HTN pivotal trial randomizing up to 433 patients to renal denervation or a sham procedure.

Additionally, the Global SYMPLICITY Registry has enrolled nearly 2,600 Spyral patients in 43 countries so far (the goal is 3,000), Townsend told the audience at a satellite session sponsored by the Cardiovascular Research Foundation.

Both "on-" and "off-" medication trials have demonstrated that the Symplicity Spyral modestly reduces ambulatory systolic blood pressure against sham controls.

Competing technologies include ultrasound denervation, notably with the Paradise system.

Other questions regarding renal denervation include durability and optimal patient selection.

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