The ‘torpedo’ that blasts nerves to cut blood pressure

ATORPEDO-LIKE device that zaps nerves with sound waves has been shown to lower high blood pressure.

When the gadget, smaller than a matchstick, is placed inside the renal artery (which carries blood from the heart to the kidneys) it fires ultrasound waves to destroy nerves in the artery walls. These play a key role in regulating blood pressure.

New research shows that destroying these nerves this way resulted in a significant drop in blood pressure.

one in three adults in the Uk has high blood pressure, or hypertension — defined as a reading of 140/90mmHg or above. As hypertension rarely causes symptoms, many of those affected don’t even realise they have a problem.

If high blood pressure is left untreated, it can lead to heart failure, stroke, heart attacks and irreversible kidney damage — treatment usually begins with lifestyle changes, such as changes to diet, reducing salt intake or losing weight.

If that does not work, drugs such as ACE inhibitors (which dilate blood vessels, easing pressure), beta-blockers (which block hormones that raise blood pressure) and diuretics (which remove excess fluid) can help. But in around a third of patients, these drugs fail to control blood pressure.

The new torpedo-technique is based on the understanding that, in some cases, hypertension is caused in part by misfiring nerves in the kidneys — which cause more salt and water to be retained, which raises blood pressure.

With the new treatment, a small incision is made in the groin under local anaesthetic and a catheter (a flexible tube) is inserted and navigated through blood vessels to the artery supplying the kidney.

Inside the catheter is a tiny torpedo - shaped device attached to an ultrasound generator at the other end.

The device itself is contained inside a balloon which, once in situ, is inflated with water so that it expands to press against the artery walls.

At the press of a button, the ultrasound is then fired around the artery for seven seconds at a time, generating sufficient heat to destroy the misfiring nerves, while the water keeps the artery walls cool to protect them from the damaging heat.

In the new study, researchers at Columbia University in the U.S. and the University of Paris in France combined the results from three trials involving more than 500 people with hypertension: the results showed that twice as many patients given the ultrasound therapy reduced their blood pressure to less than 135/85mmHg, compared with patients in placebo groups, reported the journal JAMA Cardiology in March.

Commenting on the findings, Professor Bryan Williams, a specialist in hypertension at University College London Hospitals NHS Foundation Trust and President of the International Society of Hypertension said: ‘It’s good to see this collation of data from these well- conducted studies of ultrasound-based renal denervation.

‘It confirms what individual studies have shown, that this technique lowers blood pressure, on average, by the amount of blood pressure lowering we would expect to see with a blood-pressure lowering drug.

‘The technique also appears safe in experienced hands.

‘The challenge is how to position this treatment option alongside the mainstay treatment options for high blood pressure, which are adopting a healthy diet and lifestyle, and the use of tried-and-tested blood pressure-lowering medications when needed.’