Renal Denervation Study Yields Disappointing Data
At European Society of Hypertension (ESH) Scientific Sessions, held from 14th to 17th June 2013, in Milan, Italy, study of the benefits of renal denervation for the treatment of resistant hypertension suggested that the reduction in blood pressure (BP) is smaller than observed in clinical trials and is considerably smaller when systolic BP is assessed using ambulatory BP monitoring (ABPM).
In fact, when ABPM was used to measure BP, the reduction was just one-third of that observed when assessed in the office. On average, the reduction in BP when using traditional office-cuff measurements was 17.6mm/Hg six months after renal denervation, but the reduction was just 5.9mm/Hg when assessed using 24-hour ABPM. Results from office measurement are less than what was observed in Medtronic's SYMPLICITY HTN-2 trial but still in the same range. But in SYMPLICITY, there are only few ABPM results.
In total, 109 patients with resistant hypertension were treated with renal denervation at hypertension clinics in Belgium, France, the Czech Republic, Norway, the UK, Switzerland, and Sweden. The baseline office systolic BP was 175mm/Hg, and the baseline 24-hour ABP was 157mm/Hg. At six months, office and ABPM systolic BP were reduced by 17.6mm/Hg and 5.9mm/Hg, respectively (p<0.03 for both).
As a comparison, Prof Alexandre Persu (Cliniques Universitaires Saint-Luc, Brussels, Belgium) cited the Syst-Eur trial, a placebo-controlled study of elderly patients with isolated systolic hypertension. The 24-hour ABPM reduction in systolic BP achieved with renal denervation at the ten clinical centres was just 3.9mm/Hg larger than what was observed in placebo-treated patients in Syst-Eur.
The analysis also revealed a very large variation in the response to renal denervation. In fact, a substantial proportion of patients treated with renal denervation had no change in BP at all or even showed increased systolic BP after the procedure. When measured in the office, 23 per cent of patients who received renal denervation had unchanged or higher BP six months after the procedure. Using ABPM, this proportion increased to 35 per cent, while the results were much more consistent in the active treatment arm of Syst-Eur.
Future steps, according to Persu, are randomised, controlled clinical trials that include a primary end point using ABPM. In addition, drug therapy needs to be optimised and patients need to be screened appropriately for secondary and white-coat resistant hypertension, including only those with truly resistant hypertension. In the real world, the prevalence of apparently resistant hypertension is approximately 10 to 15 per cent, according to Persu, but the proportion is significantly reduced when ABPM is used to assess BP, and the proportion of patients who will finally prove eligible for renal denervation is even lower.
New guidelines for the management of hypertension were presented at the ESH meeting and while the writing committee, comprising ESH and European Society of Cardiology experts, called renal denervation promising, the group stopped there. The guidelines state that the procedure needs more data from long-term comparison trials to establish safety and efficacy against the best possible drug regimens.