Introduction

Renal denervation (RDN) by radiofrequency ablation is a minimally invasive catheter-based technique targeting the renal sympathetic nerves which has emerged as a promising therapy for resistant hypertension since the initial Symplicity HTN-1 study was published in 2009 [1]. At the time, the role of sympathetic renal nerves in the development and course of hypertension had already been proven [2, 3] and the safety and efficacy of renal nerve ablation had been confirmed in animals models [4]. The “proof of concept” Symplicity HTN-1 trial demonstrated the safety and initial efficacy of the procedure in humans and led to the design of the first randomized trial, Symplicity HTN-2 [5]. Both trials revealed an impressive blood pressure-lowering effect and the safety of RDN [1, 5]. The 36-month long-term follow-up of the Symplicity HTN-1 study confirmed a sustained blood pressure (BP) reduction of 33/19 mm Hg [6]. These promising results were also confirmed later in many registries reporting on the effects of RDN on office and ambulatory BP [7]. Also the early results of the Global Symplicity Registry (GSR) – an open label, multi-indication registry, currently being conducted worldwide to evaluate the safety and efficacy of RDN with the Symplicity RDN System – support the view that RDN is an effective and safe procedure in reducing BP.
The Symplicity Trials and later reports led to great enthusiasm in the medical community and resulted in a consensus statement on RDN of European experts published in the “European Heart Journal” [7] followed by the position statement of the European Society of Hypertension (ESH) [8] and current ESH/ESC Guidelines for the management of arterial hypertension [9]. According to the ESH/ESC Guidelines, renal denervation may be considered as a possible treatment for patients with resistant hypertension meeting the restricted criteria for the procedure. Knowing the limitations of previous trials (including small sample sizes, limited assessment of ambulatory BP, lack of blinding, and lack of sham procedure as a control) all above-mentioned documents underlined however the necessity of a larger and properly designed, blinded trial with a masked procedure to determine the role of RDN.

Symplicity HTN-3

The Symplicity HTN-3 trial is the first blinded, randomized, sham-procedure controlled trial of RDN for treatment-resistant hypertension [10]. In March 2014 the highly surprising results of this...


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