ECG signal

Dr Diana R Holdright
MD, FRCP, FESC, FACC, MBBS, DA, BSc

Consultant Cardiologist

Dr Diana Holdright
 
 

Treatments - Renal Artery Denervation

High blood pressure or hypertension is a very common condition, affecting 30% to 40% of all adults in the UK, rising to around 70% in the over 70s age group.  The risk of coronary artery disease and stroke are directly related to blood pressure readings, and treatment to lower blood pressure is typically a combination of lifestyle changes (weight loss, regular exercise and a reduction in salt and alcohol intake) and drug therapy in the form of antihypertensives. Most patients need more than one drug, each taken at least daily, to lower their blood pressure adequately; however, in a significant proportion of patients it is not possible to lower the blood pressure to target levels despite multiple drugs at high doses.

It has been known for many years that the sympathetic nervous system (part of the “fight or flight” response, which automatically regulates many body functions) is more active than normal in patients with hypertension. Sympathetic nerves supplying the kidneys contribute to the development and perpetuation of hypertension, triggering a number of chemical pathways which aggravate the situation. The blood pressure lowering effect of blocking this sympathetic activation was demonstrated surgically as far back as the 1950s, but it is only very recently that there has been a resurgence in interest, and in particular in the use of a minimally invasive technique to block the sympathetic nerve supply to the renal arteries, the blood vessels supplying the kidneys; this is called renal sympathetic denervation.

Under local anaesthetic and sedation a tube is passed using X-ray guidance into the blood vessel in the groin and up to the renal artery. Energy, in the form of radiofrequency, is applied through the catheter within the renal arteries, effectively denervating the arteries and blocking the sympathetic signals which would otherwise operate.  Catheter-based renal denervation for the treatment of resistant hypertension has featured prominently at recent international hypertension and cardiology meetings, following initial reports that the treatment reduced blood pressure significantly with an acceptably low complication rate. However, unexpected and disappointing results from the latest SYMPLICITY HTN-3 trial have just been announced. This phase 3 study testing catheter-based renal denervation for the treatment of resistant hypertension failed to achieve its primary efficacy end point, which was a sustained reduction in systolic blood pressure at six months.1 This is in stark contrast to the very encouraging results from the earlier SYMPLICITY HTN trials which showed a significant and sustained fall in blood pressure following renal denervation. Quite why the results were not replicated in the latest study is uncertain. However, the earlier studies were not blinded since they did not include a control arm with a sham procedure, suggesting that the benefits seen in the earlier trials were potentially due to a placebo effect and not to denervation per se. As ever, this underscores the importance of meticulously designed and conducted trials prior to the introduction of new techniques in the clinical arena.

Download and print

1 http://newsroom.medtronic.com/phoenix.zhtml?c=251324&p=irol.newsArticle&ID=1889335&highlight=

Treatments - Renal Artery Denervation