Renal denervation for the treatment of resistant hypertension: review and clinical perspective

When introduced clinically 6 years ago, renal denervation was thought to be the solution for all patients whose blood pressure could not be controlled by medication. The initial two studies, SYMPLICITY HTN-1 and HTN-2, demonstrated great magnitudes of blood pressure reduction within 6 mo of the procedure and were based on a number of assumptions that may not have been true, including strict adherence to medication and absence of white-coat hypertension. The SYMPLICITY HTN-3 trial controlled for all possible factors believed to influence the outcome, including the addition of a sham arm, and ultimately proved the demise of the initial overly optimistic expectations. This trial yielded a much lower blood pressure reduction compared with the previous SYMPLICITY trials. Since its publication in 2014, there have been many analyses to try and understand what accounted for the differences. Of all the variables examined that could influence blood pressure outcomes, the extent of the denervation procedure was determined to be inadequate. Beyond this, the physiological mechanisms that account for the heterogeneous fall in arterial pressure following renal denervation remain unclear, and experimental studies indicate dependence on more than simply reduced renal sympathetic activity. These and other related issues are discussed in this paper. Our perspective is that renal denervation works if done properly and used in the appropriate patient population. New studies with new approaches and catheters and appropriate controls will be starting later this year to reassess the efficacy and safety of renal denervation in humans.