Catheter-based renal denervation (RDN) may not be superior to usual care in reducing blood pressure (BP) in patients with resistant hypertension, according to a study published March 6 in Hypertension. Further, poor medication adherence may partially explain the condition of apparent resistant hypertension.

Rosa L. de Jager, MD, et al., analyzed data from SYMPATHY, a prospective open-label multicenter trial in Dutch patients with resistant hypertension (defined as an average daytime ambulatory systolic BP measurement ≥135 mmHg, despite use of ≥3 BP-lowering agents or with documented intolerance for ≥2 BP-lowering agents). In order to assess the efficacy of RDN in resistant hypertension, patients were randomly assigned in a 2:1 ratio to usual care plus RDN or usual care alone. The trial's primary endpoint was a change in daytime ambulatory systolic BP at six months after RDN. In addition, the effect of adherence to BP-lowering drugs was explored.

Primary analyses of 139 patients showed a mean difference between RDN and control in changes in daytime ambulatory systolic BP after 6 months of 2.0 mm Hg (95 percent confidence interval, −6.1 to 10.2 mm Hg) in favor of control. In 80 percent of patients, fewer medications were detected than prescribed and adherence changed during follow-up in 31 percent of patients. In those with stable adherence during follow-up, mean difference between RDN and control for daytime systolic ambulatory BP was −3.3 mm Hg (−13.7 to 7.2 mm Hg) in favor of RDN. The authors also found that RDN as therapy for resistant hypertension "was not superior to usual care."

"Importantly, our data suggest that the direction and the magnitude of the treatment effect considerably change when medication adherence is taken into account," the authors explain.

The study's results "may have considerable societal impact," the authors conclude. Because patients are filling prescriptions but not using them, they are "staying at increased cardiovascular risk." The researchers explain that the reasons for resistance to prolonged pharmacological therapy are complex, and that moving forward, "there is great need to more extensively focus on interventions that potentially improve medication adherence."

In an editorial comment, Hillel Sternlicht, and George L. Bakris, MD, note that "Going forward, just because trials of resistant hypertension use ambulatory systolic blood pressure to exclude white coat hypertension, spectrometric evaluation of urine or blood for antihypertensive metabolites should be used to assess adherence before and during a study and should become routine."

Keywords: Antihypertensive Agents, Blood Pressure, Cardiovascular Diseases, Confidence Intervals, Denervation, Follow-Up Studies, Hypertension, Kidney, Medication Adherence, Prospective Studies, Research Personnel, Risk Factors, White Coat Hypertension

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