“Ingenious" is how a new treatment for high blood pressure has been described. It is quick, simple and so far seems to remain effective for at least three years.
Australian researchers are leading the way with this new treatment which works by silencing nerves that cause blood pressure to rise.
There appear to be no significant side effects of this procedure which is performed under local anaesthesia and allows most people to go home the same day.
At the moment, it is only available for those with intractable high blood pressure which does not respond to lifestyle changes and drug therapy.
“Intractable" means they are taking three or more drugs a day but still have systolic pressures (the top figure) between 160 and 180 millimetres of mercury.
They represent the tip of the great iceberg of Australians with blood pressure problems.
Further research is now under way to test whether this treatment would be effective in people below the waterline, who have moderate to high blood pressure, and who constitute 95 per cent of the Australian high blood pressure population.
The new treatment is a sophisticated, ultra-modern version of a crude treatment performed some 70 years ago.
The nerve connection
It has long been recognised that nerve signals from the region of the kidney are intrinsic to the process of producing and maintaining high blood pressure.
These signals go via the brain to the rest of the body, according to Henry Krum, professor of medicine and director of the Monash Centre of Cardiovascular Research and Education in Therapeutics.
Some 70 years ago, surgeons tried to silence these nerves. But rather than targeting them at the kidneys, Krum says they tried to disrupt them earlier as they left the spinal cord.
It was an imprecise process among delicate structures and left people with a wide range of side effects, from incontinence, to impotence, to being unable to adjust their posture or even stand up. But it was effective at lowering blood pressure.
When modern drug therapy came along this surgery was understandably abandoned.
But drugs don’t always work. Even after taking five a day at optimum doses and making all the appropriate lifestyle changes – becoming lean, having a low-salt diet, doing exercise and quitting smoking – in some, high blood pressure still does not budge.
Such people are at very high risk and can virtually hear their inner time-bomb ticking. They have the No. 1 global risk factor for premature death and disability, and remain at risk for strokes, heart attacks, and kidney and heart failure.
When modern catheter technology came along, it became possible to send a catheter almost anywhere in the body.
Krum says two bright innovators from New York recognised the nerve target for high blood pressure had not gone away and that it could be reached in a new non-invasive way, with a catheter. This was a paradigm shift.
Sent up through the groin, the catheter could travel to the kidneys, identify the renal nerves and silence a percentage of them with heat.
The genius of physician Howard Levin and engineer Mark Gelfand, who are inventors in cardiovascular medicine, was to recognise this opportunity.
The good fortune for Australia was that they asked our researchers to do the first trials in humans.
The perfect testing ground
Australia is known for its expertise in the sympathetic nerves of the kidneys and the role these play in high blood pressure (see story right). Australia also has good basic science and a regulatory environment which, unlike those in the United States and Europe, is not “constipated", says Krum.
He is a leader in cardiovascular therapeutics and had worked with Levin in New York. The innovative pair asked him to lead this research in Australia then co-ordinate the international trials.
The results of the first trial were published in 2009 to acclaim. They showed silencing the nerves brought systolic pressure down by about 30 millimetres of mercury.
By this stage, the effect had lasted a year. But would it endure? It was known that nerves grow back after organ transplants. Would they grow back in this case too and undo the benefit?
This November, the three-year data was published in The Lancet. It showed the benefit was not lost. Blood pressure not only stayed down but appeared to get lower over time.
Mean systolic pressure was down by 32 millimetres and diastolic (the lower number) by 14 millimetres. Krum says 10 per cent of people were defined as “non-responders" because their systolic drop was less than 10 millimetres.
The results showed age, renal impairment and diabetes had no significant impact on the way people responded.
But as the starting pressures of this population were so high, people remained on their medication throughout the process and are still on it.
How this will play out in people with less dramatic blood pressure is still unknown. “Ask me again in five years," says Krum. Around 30 per cent of Australians are said to have high blood pressure.
The procedure, known as renal denervation, is available in all capital cities but is not covered by Medicare. It costs between $10,000 and $12,000.
The Australian Financial Review