Blood pressure op may be life-saver

BRONWYN TORRIE
Last updated 05:00 16/06/2013
Fletcher Allen

A new "renal denervation" procedure offers lasting and significant control with a very low risk of complication

Cardiologist Dr Scott Harding
KENT BLECHYNDEN/Fairfax NZ
STEP FORWARD: Cardiologist Dr Scott Harding, who has performed the first renal denervation procedures.

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A simple 20-minute operation to treat high blood pressure is being trialled in New Zealand, and has the potential to reduce the risk of killer strokes and heart attacks.

There is currently no effective treatment for resistant hypertension - when drugs don't work to lower high blood pressure - but a new surgical device being tested in a world-first study at Wellington Hospital could change this.

Cardiologist Dr Scott Harding performed the first renal denervation procedures on two patients last month using a new multi-electrode catheter, which zaps overactive kidney nerves responsible for raising blood pressure.

It takes about 20 minutes, compared to the single-electrode procedure that takes about an hour.

Harding believes it is a "big step forward" in treating high blood pressure.

About 5000 people around the world have been successfully treated with a single-electrode catheter. "So far the results are surprisingly good; the procedure lowers blood pressure by about 20-30 millimetres of mercury, which is the equivalent of about two to three drugs."

An immediate change in blood pressure isn't expected, but the results can last for years. "It's not like flipping a switch, you get this gradual improvement in blood pressure over a period of a month to a year."

About 10 per cent of New Zealanders are affected by resistant hypertension, which often has no symptoms but increases the risk of stroke, heart attack and kidney failure, he said.

Forty patients will have the multi-electrode procedure as part of a world-first study that also involves two Melbourne hospitals.

The study is being funded by medical device company Medtronic, which developed the Symplicity Spyral multi-electrode catheter.

Harding said the new technology was "based on old science".

Renal denervation was initially performed in the middle of last century, but the open surgery was fraught with problems and had terrible side-effects, including fainting when standing up.

"So then the drugs came along and everyone thought they were great," Harding said.

But the small group of people whose high blood pressure could not be lowered by medication remained a problem.

Wellington patients have been able to access the single-electrode procedure for about a year as part of research studies.

It is not publicly funded, nor is it covered by health insurance because it's so new, Harding said.

However, people can pay about $17,000 for the procedure to be done at a private hospital in the capital and one in Auckland.

The multi-electrode procedure is faster than the single-electrode as burning time is one minute on each side, compared to six minutes. It isn't as painful for patients as the burning time is reduced and, because it's faster, they may be able to go home the same day, he said.

"It will make it easier to do, hopefully more consistent and more comfortable for the patient and easier to fit into [surgical] schedules."

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People who suffer bad side-effects from blood pressure pills could also become candidates for this non-invasive procedure.

The same technology will be trialled in Wellington, Auckland, Singapore and Melbourne for the treatment of diastolic heart failure - when the heart loses the ability to relax and fill with blood.

"The whole concept, when it was first explored, was for a treatment of heart failure but along the way it was so effective for blood pressure lowering, that got developed first," Harding said.

It could also be used to treat other rhythmic disturbances to the heart, insulin resistance in diabetics and possibly sleep apnoea.

HOW IT WORKS BLOOD PRESSURE

 

A long catheter is inserted into the femoral artery in the upper thigh and is threaded through the renal artery near each kidney.

Once in place, a wire is released to create a spiral along the artery that leads to the kidney.

A low-power radio frequency energy is switched on for one minute to burn the nerves lining the walls of the artery.

These nerves impact the sympathetic nervous system, which affects the major organs responsible for regulating blood pressure - the brain, heart, kidneys and blood vessels.

The procedure is done on the left and right side of the kidney and results in hyperactive renal nerves being calmed, which in turn causes a reduction in the kidneys' production of hormones that raise blood pressure.

The patient is awake during the procedure but heavily sedated.

The ideal blood pressure for most people is under 130/80. Generally, hypertension is defined as having blood pressure of 140/90 or higher.

Blood pressure tests measure the force of blood against artery walls as it travels around the body. The higher the pressure, the more risk of heart attacks, strokes and kidney failure.

- Sunday Star Times

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