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Burning the nerves around the kidneys could permanently lower blood pressure among people who don’t respond well to medication.

For decades, the kidneys’ nerves have been known to regulate blood pressure. So-called renal denervation involves inserting a catheter into the thigh’s femoral artery to access the arteries that feed the kidneys. Applying radio wave pulses burns the nerves in the artery walls, reducing their activity.

The technique has shown promise as a treatment for high blood pressure, but there is a lack of data on its safety and long-term efficacy. To find out more, at Saarland University in Saarbrücken, Germany, and his colleagues looked at 80 people who had high blood pressure, despite taking antihypertension drugs. Thirty-eight of the participants underwent renal denervation and 42 had a sham procedure, acting as the control group.

At the start of the study, all the participants’ systolic pressure – the force at which the heart pumps blood around the body – was between 150 millimetres of mercury (mmHg) and 180 mmHg. Anything above 140 mmHg . Their diastolic pressure, the resistance to blood flow in the blood vessels, was at least 90 mmHg, the upper end of a healthy reading.

Three years after the procedure, the renal denervation participants’ systolic and diastolic blood pressure readings were 10 mmHg and 5.9 mmHg lower, respectively, than their sham group counterparts. Most of the participants continued to take blood pressure-lowering drugs throughout the study.

No safety issues were linked to renal denervation over the three years.

Exactly how renal denervation works isn’t well understood. Mahfoud and his team suggest the shock to the nervous system may reconfigure the body’s blood vessels or affect hormone systems in the kidneys that control blood pressure. High blood pressure raises the risk of heart attacks and strokes, among other medical conditions.

Speaking of the systolic reduction in particular, the team described the result as “clinically meaningful and thought to be associated with lower rates of cardiovascular events”.

Not everyone is entirely convinced of renal denervation’s potential in the clinic, however.

“The numbers are quite small in this paper, but it did look as if renal denervation lowered blood pressure more than the sham control,” says at the University of Manchester, UK.

Renal denervation will probably only be targeted at people who are resistant to medication, says Heagerty, because it is an expensive procedure and generic drug therapy is relatively cheap.