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RESEARCH PRODUCT

Proceedings from the European clinical consensus conference for renal denervation: considerations on future clinical trial design: Figure 1

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Approximately 8–18% of all patients with high blood pressure (BP) are apparently resistant to drug treatment.1,2 In this situation, new strategies to help reduce BP are urgently needed but the complex pathophysiology of resistant hypertension makes this search difficult. Not surprisingly in this context, the latest non-drug treatment which triggered controversy is catheter-based renal denervation (RDN).3,4 The method uses radiofrequency energy, or alternatively ultrasound or chemical denervation, to disrupt renal nerves within the renal artery wall, thereby reducing sympathetic efferent and sensory afferent signalling to and from the kidneys.5,6 Various experimental models of hypertension strongly support this concept7,8 and available evidence also suggests that sympathetic nervous system activation contributes to the development and progression of hypertension and subsequently to target organ damage.7–11 Historical observations have shown that surgical sympathectomy can reduce BP as well as morbidity and mortality in patients with uncontrolled hypertension.12,13 However, the clinical evidence in support of RDN as an effective interventional technique in patients with resistant hypertension is conflicting. A number of observational studies and three randomized, controlled trials (Symplicity HTN-2, Prague-15, and DENERHTN) support both safety and efficacy of this new therapy14–22 but some smaller studies and the large, single-blind, randomized, sham-controlled symplicity HTN-3 trial failed to show superiority of RDN when compared with medical therapy alone.23–25 Whatever the shortcomings of individual trials may be, the possibility remains that the observed BP responses were due to placebo response, the Hawthorne effect, regression to the mean, unknown co-interventions or other bias.26 The design, conduct, and interpretation …