Drug-resistant Hypertension: Is Renal Sympathetic Denervation the Answer?

Trial: Symplicity HTN-2 Investigators, Esler MD, Krum H, et al.: Renal sympathetic denervation in patients with treatment-resistant hypertension (The Symplicity HTN-2 Trial): a randomized controlled trial. Lancet 2010, 376:1903–1909. Rating: ••Of major importance. Introduction: Sympathetic overactivity is thought to be a major contributor to the pathogenesis and progression of human hypertension [1, 2]. In particular, renal sympathetic activation results in renal vasoconstriction, increased renin secretion, and enhanced sodium and water reabsorption, all of which contribute to the development of hypertension [3]. Despite this mechanistic understanding, attempts at modulating sympathetic tone with antiadrenergic drug therapy have been limited by their poor clinical performance and undesirable side-effect profile [1, 4]. Additionally, historic surgical approaches for the treatment of hypertension with renal sympathectomy have long been abandoned due to a high perioperative morbidity and mortality [5, 6]. In recent years, the advent of a catheter-based technique using radiofrequency to destroy the renal nerves has revitalized these long abandoned thoughts of treating hypertension with renal denervation. Following encouraging results of an uncontrolled feasibility trial and a case report [7, 8], a recent randomized controlled trial (Symplicity HTN-2 [Renal Denervation in Patients With Uncontrolled Hypertension]) has further demonstrated the potential for catheter-based renal denervation in the treatment of drug-resistant hypertension. Aims: The Symplicity HTN-2 trial was designed to determine the safety and effectiveness of catheter-based renal artery denervation with the Symplicity Catheter System (Ardian, Palo Alto, CA) in reducing blood pressure in patients with drug-resistant hypertension. Methods: In this multicenter trial (involving 24 centers in Europe, Australia, and New Zealand), 106 patients ages 18 to 85 years with a systolic blood pressure of 160 mm Hg or more (≥150 mm Hg in patients with type 2 diabetes), despite treatment with three or more antihypertensive medications were randomized to undergo renal denervation while continuing prior drug therapy or to continue prior drug therapy alone. Patients who met initial screening criteria were subsequently excluded from the trial if their blood pressure fell below eligibility criteria at a second clinic visit after a 2-week screening phase. During this phase, patients were required to document medication compliance and twice-daily home blood pressure monitoring. Patients were also excluded if they were found to have unfavorable renal artery anatomy on imaging; other exclusion criteria included an estimated glomerular filtration rate of less than 45 mL/min/1.73 m2 and type 1 diabetes. The trial’s primary end point was the change from baseline in seated office-based measurement of systolic blood pressure at 6 months. During the intervention, the catheter was advanced into the renal arteries and four to six discrete low-power radiofrequency treatments were applied along the length of both renal arteries. Background use of antihypertensive drugs was held constant for the duration of the trial in both groups. Results: At baseline, the groups were well matched on most characteristics: office blood pressure was 178/96 mm Hg in the intervention group (n = 52) and 178/97 mm Hg in the control group (n = 54). Office-based blood pressure fell by 32/12 mm Hg (SD 23/11; P < 0.001) in the patients who underwent renal denervation versus no change in the control group (1/0 mm Hg, SD 21/10; P = NS). Home blood pressure fell by 20/12 mm Hg (SD 17/11) in the renal denervation group (n = 32) versus no change in the control group (n = 40). Twenty-four-hour ambulatory blood pressure fell by 11/7 mm Hg (SD 15/11; P < 0.006) in the renal denervation group (n = 20) versus no change in the control group (n = 25). There were no serious procedural complications in the denervation group and no between-group differences in renal function or in the incidence of adverse events. Discussion: The authors concluded that renal artery denervation is safe and effective in reducing office blood pressure, home blood pressure, and 24-h blood pressure at 6 months in patients with drug-resistant hypertension.