Pushing the boundaries of renal denervation for resistant hypertension

A proportion of patients with hypertension continue to have elevation of blood pressure resistant to treatment with several medication classes. This situation causes great concern to physicians and patients alike, with relatively few options once maximally tolerated medical therapy has been exhausted. While exact estimates of the prevalence of resistant hypertension vary, it appears that approximately 10–15% of patients in an outpatient cardiovascular referral population have this condition [1]. In patients with resistant hypertension, initial studies of catheter-based renal denervation have shown significant reductions in blood pressure that appear to be sustained through at least 2–3 years [2]. An ongoing randomized clinical trial aims to establish the efficacy and safety of renal denervation for resistant hypertension in a rigorous fashion [3]. The studies to date have largely focused on patients with baseline office systolic blood pressure 160 mm Hg (or in some studies 150 mm Hg in diabetic patients). Therefore, the effects of renal denervation in patients with office systolic blood pressures of 140–160 mm Hg are not well characterized. In this issue of Catheterization and Cardiovascular Interventions, Kaltenbach et al. present their series of 20 consecutive patients with office systolic blood pressures of 140–160 mm Hg on an average of 5.4 antihypertensive drugs [4]. Ten of the patients had diabetes, two of whom were insulin dependent. Four patients had peripheral artery disease. The procedure was successfully completed in all 20 patients, with no procedural complications, no significant reductions in renal function, and no renal artery stenosis seen on 6-month follow-up ultrasound. The baseline office blood pressure was 148/83 mm Hg and decreased by 13/5 mm Hg at 6 months (P <0.01 for systolic blood pressure change, the primary endpoint) and the effect was more pronounced at 6 months than at 3 months. The mean ambulatory 24-hr blood pressure was reduced by 11/4 mm Hg (P <0.01) over 6 months. Four patients were able to reduce antihypertensive medications because of normalization of blood pressure. Sixteen patients experienced blood pressure reductions, with 15 patients achieving a systolic blood pressure less than 140 mm Hg. Eleven patients had a reduction in systolic blood pressure reduction of more than 10 mm Hg compared with baseline. Thus, the observed reductions in blood pressure were in a clinically meaningful range. This important and carefully conducted pilot study establishes the safety of renal denervation in milder cases of resistant hypertension. As such, it significantly pushes the boundaries of catheter-based renal denervation and is a major conceptual advance. This study also indirectly supports the safety of proceeding with evaluation of renal denervation in patients without extreme blood pressure elevations for indications such as heart failure or chronic renal insufficiency [5]. Of course, a larger, randomized, multicenter trial will be necessary before broad adoption of renal denervation in patients with blood pressures in the 140–160 mm Hg range. Questions remain about which patients may respond and whether this rate can be improved. Furthermore, the operators in this study have a large amount of experience with renal denervation and the results may not be