It remains unclear whether renal denervation will effectively change the way hypertension is treated in everyday clinical practice.

Catheter-based sympathectomy for hypertension may be suitable for people who have resistant hypertension, who may be on three or even four medications and are still not achieving control. This therapy denervates the kidneys and it has been shown to bring about a sizable reduction in blood pressure in the follow-up period of a year to 18 months.

The results of the Symplicity study (Prof Esler Murray et al) have generated great interest, and the investigators may have paved the way for interventional management of patients with resistant hypertension. ???The Symplicity trial studied people with resistant hypertension,??? said Prof Edward Johns, Head of UCC??™s Department of Physiology.

???These are very exciting times. Questions arise as to whether this approach might also confer benefits to patients with other types of hypertension ??” essential hypertension, for example.???

It has been shown that catheter-based renal denervation can safely be used to substantially reduce blood pressure in treatment-resistant, hypertensive patients. Non-selective surgical sympathectomy was effectively used as a treatment of severe hypertension before antihypertensive drugs became generally available.

Nerve activation
Activation of renal sympathetic nerves is key to the pathogenesis of essential hypertension. The Symplicity authors aimed to assess the effectiveness and safety of catheter-based renal denervation for reduction of blood pressure in patients with treatment-resistant hypertension. Previous studies have also shown a significant reduction in blood pressure can be achieved with catheter-based renal denervation in patients whose essential hypertension was uncontrolled, despite treatment with three or more antihypertensive drugs.

In the Symplicity HTN-2 trial, renal denervation resulted in impressive reductions in mean, office-based measurements of blood pressure (32/12mmHg at six months). It is thought that the trial data may provide opportunities to develop novel compounds targeting sensory nerves in the kidneys.

Revolutionary?
Although renal denervation might prove to be a revolutionary treatment for hypertension, the complexity of its pathophysiology makes it unlikely that inhibition of one factor will be effective in all patients, and over-optimism should be avoided, the study authors state.

Recently-developed endo-vascular catheter technology enables selective denervation of the human kidney, with radio-frequency energy delivered in the renal artery lumen, accessing the renal nerves located in the adventitia of the renal arteries.

A first-in-man study of this approach showed successful renal denervation with reduction of sympathetic activity and renin release, in parallel with reductions of central sympathetic outflow. Safety and feasibility trials of this procedure identified substantial reductions of blood pressure without substantial procedure-related complications, the authors reported.

A 33/11mmHg reduction in blood pressure was noted in the renal denervation group compared with the control group, during the six-month follow-up.

In the Symplicity study, renal denervation led to a reduction in blood pressure of 10mmHg, or more in 84 per cent, of treated patients.

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Irish Medical Times