Evidence gap on renal denervation closing while procedure widely used, German study finds

Renal denervation procedure image courtesy of Medtronic
Renal denervation procedure image courtesy of Medtronic

An abstract presentation during EuroPCR 2013 (21–24 May, Paris, France) focused on assessing the number and quality of published clinical trials underpinning the wide use of renal denervation in Germany. It strongly made the point that in the past, clinical trial data on the procedure had been scarce and that the long-term durability of treatment effects had not been proven in a large number of patients.

The abstract written by Michael Weisser and Ute Zerwes, from a company entitled Assessment in Medicine, Loerrach, Germany, highlighted that renal denervation, although new, was already a widely used procedure. The abstract noted: “In Germany alone, more than 2,000 performed cases were officially registered by the Federal Statistical Office in 2011”.

It also expressed the fact that the procedure was increasingly being used in real-life clinical practice even though there had been a lack of high-level evidence. “Obviously, care providers do not rely on published clinical evidence for this treatment alone, [but] the gap between available clinical evidence and current extent of application of this treatment has to be closed by further clinical trials from an evidence-based medicine point of view,” the study said, taking the perspective of a potential Health Technology Assessment stakeholder.

Weisser and Zerwes carried out a literature review in June 2012, which incorporated a high level of search sensitivity, analysing publications about renal denervation in patients with resistant hypertension.

They included clinical studies with outcomes for ≥10 patients, guidelines, expert consensus statements, position papers and systematic reviews. The review included publications in English, German, French, Italian and Spanish. They excluded publications that focused on diagnosis of renal hypertension and/or haemodialysis and animal studies. They also excluded case reports, reviews, letters, comments, news and editorials.

The researchers searched Medline and all databases provided by The Cochrane Library and chose 18 publications as being potentially relevant. These were screened in full text, and then 12 were found to be relevant as they directly reported results of different clinical trials. In this set of publications there was one randomised controlled trial and 11 non-randomised trials.

“All trials together included less than 500 patients who had actually received the treatment according to author statements. No publication was able to provide outcome parameters for a follow-up period of more than two years. The clinical trial involving the highest level of evidence, ie. the randomised controlled trial, only provided a follow-up of six months,” the abstract stated.

During the oral presentation on May 23rd in Paris, Weisser pointed out that the evidence gap was closing as one year clinical trial data of the quoted randomised study were published six months after the review was carried out. Furthermore, there were 28 randomised, controlled trials known and listed at clinicaltrials.gov by the time of the presentation, Weisser said, which would very likely close the gap seen in the past. He also made the point that there were no reimbursement incentives for the strong use of the procedure in Germany, making it likely that the high clinical need had driven the development experienced.