"The aim is not necessarily to get rid of medication completely but to make the blood pressure medication-controlled," said Mercy cardiologist Professor John Ormiston, who is involved in the trial. "Many patients are able to reduce their medication."
The treatment is a form of renal de-nervation, which interferes with nerves in the outer walls of arteries supplying the kidneys by damaging them with heat. Around 14 bursts of ultrasound energy, each lasting 15 seconds, are aimed at each of the two renal arteries.
Separately, ultrasound - guided by magnetic resonance imaging - is also used to treat uterine fibroids and is being trialled in the treatment of various cancers.
The renal nerves are part of the sympathetic nervous system which links the main organs responsible for blood pressure regulation. In people with high blood pressure, the sympathetic nervous system is overactive. Renal de-nervation was catching on as a treatment done with a catheter inserted into a blood vessel at the groin and threaded up to the renal arteries.
However, this technique suffered a blow when a trial involving more than 500 patients found that the reduction in average blood pressure at six months was not statistically significantly greater in the treatment group than in those given a sham version of the procedure.
Professor Ormiston said he stopped performing the catheter-based procedure after the study results were published in March.
However, he suspected factors such as some doctors' relative inexperience with the procedure had weakened the results.
Treatment gives retiree his life back
Ray Brokenshire's blood pressure began spiralling out of control last October.
The condition put the retiree, of Temuka in South Canterbury, in Timaru Hospital's intensive care unit and Christchurch Hospital's coronary care unit after he began passing out.
Ray Brokenshire.
He was on seven medicines to control his blood pressure but was still suffering terrible headaches and dizzy spells.
"I just lost any control of my life. I couldn't drive, I couldn't read the newspaper. I would be sitting there working on my computer and my blood pressure would go up and I couldn't even see the screen. I'd collapse and the ambulance would be called."
Over Christmas while he was in Timaru Hospital, a United States doctor mentioned a trial sponsored by a US company and put him in touch with Auckland cardiologist Professor John Ormiston.
Mr Brokenshire, 67, was admitted to the trial and several weeks ago, at no cost to him, received the treatment - ultrasound ablation using sound waves to permanently impair over-active nerves in the arteries supplying the kidneys.
"I can't stop smiling," he said, "because I got my life back."
How effective
42 patients treated in two trials of Kona Medical's ultrasound system for drug-resistant high blood pressure
73% had a clinically significant drop in blood pressure at three months
81% at six months
Source: Kona Medical
