More Proof: Renal Denervation Success Depends on Total Ablation

Marlene Busko

September 01, 2014

BARCELONA — There's more evidence that success in patients with resistant hypertension who undergo renal denervation depends on ablating all accessory renal arteries[1].

That comes from a series of 66 patients with resistant hypertension who underwent the procedure; two-thirds "responded" with systolic blood-pressure drops of more than 20 mm Hg at six months. Of the 42 patients who responded, 38 had complete ablation and four had incomplete ablation.

"If the patient has small renal arteries that are not accessible, which is frequently the case, it will not be possible to perform a complete ablation," so renal denervation will not have the desired effect, Dr Linda Schmiedel (Technische Universitat Dresden, Germany) said in a press conference here at the European Society of Cardiology (ESC) 2014 Congress . The procedure can be effective, but success depends on careful patient selection and complete ablation, she said.

The negative SYMPLICITY HTN-3 trial had suggested that renal denervation is "dead in the water," but this study is somewhat encouraging, although the procedure is far from ready for prime time, and clinicians should focus on other ways to treat resistant hypertension, two experts say.

"The results were good, but not impressive . . . but there is hope," session cochair Prof Joep Perk (Linnaeus University, Health and Caring Sciences, Kalmar, Sweden) told heartwire . "What I think this will mean is that we'll get a boost in the technology to do the whole procedure more precisely and do what the anatomy asks you to do," he said. If he were a policy maker, he would say, "Let's get the technology better in a large amount of people before we start to roll it out."

Prof Joep Perk

"In March, when the SYMPLICITY HTN-3 trial was published, there was no efficacy; now we have heard that there is a more efficient approach—that you do not only intervene in the main renal artery, but if there are accessory ones, that you consider them also," ESC spokesperson Prof Heinz Drexel (VIVIT-Institut, Feldkirch, Austria) noted to heartwire . Research "should go on," he continued, but stressed that drug therapy should not be overlooked in the meantime. "I think the mineral corticoid-receptor antagonists are not used enough," he said.

Of note, longer-term results from SYMPLICITY-HTN 3 are also being reported today at ESC 2014. Other experts have already stressed that better patient selection and more effective technology and technique may be the way forward for renal-denervation therapy, which is widely available in some European countries but as yet not approved in the US.

Going Back to Basics: Anatomy Matters

Dr Linda Schmiedel

Resistant hypertension—defined as blood pressure that remains above 140/90 mm Hg despite adhering to full doses of an appropriate three-drug treatment regimen that includes a diuretic—greatly increases risk of cardiovascular events, Schmiedel noted. The risk doubles with each blood-pressure increment of 20/10 mm Hg, making effective blood-pressure treatment vital.

In 2009, it appeared that decreasing renal sympathetic-nerve activity by performing point-by-point radiofrequency application in the main renal arteries might be a solution. In SYMPLICITY HTN, the procedure reduced blood pressure by 23/11 mm Hg, she noted.

But in these studies, renal denervation was performed in normal arteries that were more than 20 mm long and 4 mm in diameter, and not in accessory renal arteries, which have a small diameter that would increase the risk of developing a vascular stenosis.

The researchers sought to determine whether the absence of radiofrequency ablation in accessory arteries might affect blood-pressure control attained at six months after surgery.

They performed renal denervation in 110 patients (58% men) with a mean age of 65 who had a mean ambulatory blood pressure of 154/85 mm Hg and were taking more than six antihypertensive drugs.

Six months after the procedure, 66 patients were available for follow-up and had office and 24-hour ambulatory blood-pressure measurements.

About a third of the patients (24) did not respond, and their office blood pressure increased by about 14 mm Hg.

Patients with complete ablation had a greater blood-pressure reduction with renal denervation (18/5 mm Hg) than those whose ablation was not complete (12/3 mm Hg), but the difference was not significant (p=0.67).

The procedure costs about €4000, Schmiedel said. In reply to a question asking what she would offer a patient with resistant hypertension, she said she would perform a 3D MRI to see whether the patient had inaccessible accessory arteries, which would rule out renal denervation.

"If you cannot really denervate the whole arterial branch, you still have a few arteries that trigger hypertension," Perk noted. Like Drexel, he feels that resistant hypertension can be better controlled with existing antihypertensives. "There are very few patients [with hypertension that cannot be controlled], but it takes time [and] effort," he added. Swedish guidelines recommend that patients buy a device to monitor their blood pressure at home, much like diabetic patients monitor their glucose, he said, which greatly improves compliance.

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