Resistant hypertension is an increasingly prevalent health problem associated 
with important adverse cardiovascular outcomes. The pathophysiology that 
underlies this condition involves increased function of both the sympathetic 
nervous system and the renin-angiotensin II-aldosterone system. A crucial link 
between these 2 systems is the web of sympathetic fibres that course within the 
adventitia of the renal arteries. These nerves can be targeted by applying 
radiofrequency energy from the lumen of the renal arteries to renal artery walls 
(percutaneous renal sympathetic denervation [RSD]), an approach that has 
attracted great interest. This paper critically reviews the evidence supporting 
the use of RSD. Small studies suggest that RSD can produce dramatic blood 
pressure reductions: In the randomized Symplicity HTN-2 trial of 106 patients, 
the mean fall in blood pressure at 6 months in patients who received the 
treatment was 32/12 mm Hg. However, there are limitations to the evidence for 
RSD in the treatment of resistant hypertension. These include the small number 
of patients studied; the lack of any placebo-controlled evidence; the fact that 
blood pressure outcomes were based on office assessments, as opposed to 24-hour 
ambulatory monitoring; the lack of longer-term efficacy data; and the lack of 
long-term safety data. Some of these concerns are being addressed in the ongoing 
Renal Denervation in Patients With Uncontrolled Hypertension (Symplicity HTN-3) 
trial. The first percutaneous RSD system was approved by Health Canada in the 
spring of 2012. But until more and better-quality data are available, this 
procedure should generally be reserved for those patients whose resistant 
hypertension is truly uncontrolled.