Zapping a nerve with radio waves could soon be used routinely to reduce blood pressure in people whose hypertension fails to respond to drugs. This would cut the risk of stroke and heart disease for hundreds of thousands of people.
The procedure targets nerves surrounding the kidney, which are housed within the wall of the renal artery. The radio waves are delivered to the inside of the artery via a probe inserted through the patient鈥檚 upper thigh.
Murray Esler of the in Melbourne, Australia, a leading member of the research team that has be trialling the procedure, says these nerves 鈥渁re really switched on鈥� in hypertensive patients. They increase blood pressure by promoting salt and water retention, and constricting blood vessels.
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To switch them off, Esler and his team used the radio-wave probe to heat the artery by 10鈥壜癈. This reduced the activity of the nerve by between 30 and 80 per cent, while leaving the artery itself unharmed.
Millions at risk
Hypertension is said to occur when a person鈥檚 systolic blood pressure rises above 140 millimetres of mercury and the diastolic pressure is above 90 mmHg. It is known to increase the risk of stroke and coronary heart disease. Worldwide, 7.1 million deaths per year are directly attributed to uncontrolled blood pressure.
Conventional drug treatments work by helping blood vessels to relax. However, 15 per cent of hypertensive patients do not respond to these drugs.
The trial involved 106 patients with systolic blood pressure of more 160 mmHg and taking three or more anti-hypertensive drugs. The normal level is 120 mmHg. Around half underwent the procedure.
After six months, the systolic blood pressure had fallen by at least 10 mmHg in 84 per cent of those who received the treatment. This is expected to reduce their risk of stroke by more than 30 per cent. Esler is unsure why it was not effective for all patients. He speculates that some were not 鈥渮apped enough鈥�.
On average, the systolic blood pressure in those who were treated dropped by 32 mmHg and the diastolic pressure by 12 mmHg, while the blood pressure in the control group was unchanged. The researcher found no serious side-effects.
The results have impressed , a cardiologist at the University of Sydney, Australia, who was not involved in the study. 鈥淭his offers a completely new approach to people who are otherwise resistant to treatment,鈥� he says.
Lasting effect
The procedure was on one man in 2008, and his blood pressure remains lower. So the treatment 鈥減robably will be permanent鈥�, Esler says.
, a specialist in vascular medicine at the University of Sydney, says that if the treatment does prove to be permanent it will have 鈥減rofound implications for patients鈥� currently required to undergo frequent clinical check-ups.
The treatment should available for routine clinical application in Europe and Australia within the next 12 months, the team say.
Neal points out, however, that the effect will need to be repeated in bigger groups and the long-term effects assessed in more detail.
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