Australasian Science: Australia's authority on science since 1938

Nerveless Blood Pressure Control

By Stephen Luntz

An old method for controlling blood pressure has finally come of age thanks to more refined surgical techniques, according to research published in The Lancet.

High blood pressure causes 7.5 million deaths per year and affects at least one-quarter of the population aged over 25. While the underlying causes lie in a mix of genetics, diet and lack of exercise, a set of nerves around the kidney act as the trigger. In the 1930s it was discovered that blood pressure could be lowered if these nerves were disrupted.

Unfortunately, surgical techniques at the time were so crude that plenty of other nerves got cut as well, resulting in side-effects such as impotence and dangerously low blood pressure upon standing up. When drugs for hypertension were invented, surgery was dropped.

However, drugs have their own problems and in recent years a form of surgery called radiofrequency ablation has been developed whereby a catheter transmits energy to the target nerves in the distal artery, causing highly focused damage. However, the long-term effectiveness of radiofrequency ablation has been unclear.

Lancet lead author Prof Henry Krum of Monash University followed up a group of patients who had been resistant to other treatments for hypertension, but whose blood pressure had fallen in the 6 months after surgery. He found the benefits continue for at least 3 years.

“These findings support the durability of the procedure and its clinical utility in a group of severe hypertensive patients who have run out of further treatment options,” Krum says. He admits that “one downside is it is not reversible,” but notes it is rare for blood pressure to drop enough for this to be an issue.

While the destruction of nerve cells may seem alarming, Krum says the only common side-effects are those associated with any major surgical procedure, and the impact on the wallet. Radiofrequency ablation costs around $10,000 and is not currently covered by Medicare, but Krum hopes this will change now that its effectiveness has been established.

The same technique is sometimes used to suppress nerve activity in the heart, and to reduce the pain of pancreatic conditions.