Renal sympathetic efferent and afferent nerves are crucial for the initiation and maintenance of systemic hypertension, and as such renal sympathetic denervation is a potential therapeutic target for hypertension.Krum et al. describe the development of a novel, percutanoeus, catheter-based approach to renal sympathetic denervation.The lumen of the main renal artery is cannulated and the surrounding sympathetic nerves destroyed by radiofrequency waves, and in a swine model this technique has been shown to reduce noradrenaline content in the kidney by as much as 85%.

Fifty patients received percutaneous radiofrequency catheter-based treatment between June 2007 and November 2008, with subsequent follow-up to 1 year. The primary endpoints were office blood pressure and safety data at 1,3,6,9, and 12 months after the procedure. Both renal and magnetic resonance angiography were performed to ensure no anatomical damage from the procedure, and blood-pressure lowering effectiveness was assessed by repeated measures ANOVA. 5 patients were excluded from treatment for anatomical reasons (such as the presence of dual renal artery systems).

Following the procedure, a significant and progressive reduction in blood pressure was observed over the 12 months since treatment (figure 1); by comparision the 5 patients not treated showed a mean rise in blood pressure. Baseline and six-moth glomerular filtraion rate data were available for 25 patients, and showed a mean increase from 79 to 83mL/min/1.73m2. One intraprocedural renal artery dissection occurred before radiofrequency energy delivery, without further sequelae, and there were no other renovascular complications.

This was a proof-of-concept study, and as such lacks a control group.Furthermore, in an age of advanced pharmacotherapy for hypertension, can an invasive approach ever be completely justifiable?It is most likely that this technique will evolve to have a role in those with truly resistant hypertension.

·Krum H, Schlaich M, Whitbourn R, et al. Catheter-based renal sympathetic denervation for resistant hypertension: a multicentre safety and proof-of-principle cohort study. Lancet 2009; published online March 30. DOI:10.1016/S0140-6736(09)60566-3

· Interventional management of resistant hypertension. Doumas M, Douma S. Lancet 2009; published online March 30. DOI:10.1016/S0140-6736(09)60624-3