Pioneering study a bid to prove implants a safe and effective remedy for hypertension that medicine can't ease.
In a pioneering trial, New Zealand patients are having electrical discs implanted in their arms to try to reduce life-threateningly high blood pressure that resists medication.
More than a quarter of adults have high blood pressure - hypertension - and in up to 10 per cent of this group the condition is resistant to drug treatment. High blood pressure increases a person's risk of heart attack, stroke and kidney failure.
The trial - the first time the device has been tested in humans - involves implanting a battery-powered disc about the size of a $2 coin in each lower arm just under the skin and overlying the median nerve, one of the arm's major nerves.
The "neuromodulation" device emits a series of electrical impulses for 30 minutes once a week.
The aim is to calm the over-activity of the part of the nervous system associated with the fight-or-flight and stress responses - and consequently to relax the constriction of blood vessels.
Resting blood pressure increases with age. It is generally considered to be high when above 140mm of mercury at the peak of the heart's pumping cycle to the body (systolic) or above 90 between pumping cycles (diastolic).
One of the trial participants, Lionel Petersen, 68, said the devices, implanted in his arms under local anaesthetic three months ago at Auckland City Hospital, produced a pins-and-needles sensation when they were operating.
His systolic blood pressure had dropped to "the 140s and 150s", from 190 to 200 before the trial.
"Since this device has gone in, there's been a dramatic lowering. It's looking good," said Mr Petersen, a Waikato District Council member and retired police officer, of Tuakau, south of Auckland.
He understood that if his blood-pressure reduction was confirmed during the two-year trial, his hypertension medication might be gradually reduced.
He takes six kinds of pills - four for blood pressure, a blood-thinner and one to lower his cholesterol level.
The leader of the New Zealand trial, Dr Mark Webster, a cardiologist at Auckland City Hospital, said the prospect of establishing the device as a safe and effective treatment was exciting.
"It may be possible in future to reduce the number and/or dosage of blood pressure medications in some people, but that needs to be shown."
The idea behind the trial was to interfere with the body's so-called "sympathetic nervous system" and its constriction of blood vessels. The site at which the devices were implanted was the same as that used in acupuncture to treat hypertension.
Dr Webster said the concept of the arm discs' effect was the same as in the procedure called "renal de-nervation", a treatment for drug-resistant hypertension in which nerves to the kidney were blocked using radio frequency energy.
Mr Petersen said his doctor referred him to the trial programme as an alternative to increasing the dosage of his blood pressure medication. He had previously had a side-effect - fluid retention that caused his feet to swell up "like balloons", leaving him unable to stand up.
The trial will include 110 patients at the Auckland City, North Shore, Middlemore, Wellington and Christchurch hospitals, as part of an international collaboration with hospitals in Canada and Taiwan.
How it works
* Battery-powered discs produce a small electrical impulse.
* Implanted into lower arms.
* Thought to relax blood vessels, helping to reduce blood pressure.