Researchers measure heart nerve signals

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AUSTRALIAN scientists have for the first time measured nerve signals being sent to the heart, in a breakthrough they hope will lead to better treatments for people who suffer heart attacks.

Scientists placed micro-electrodes into the nerves leading to the heart and kidneys of sheep to accurately measure the impulses - with immediately unexpected results.

Despite the heart's vital and unceasing work, during times of rest the brain directs more sympathetic nerve activity at the kidneys than the heart.

"We found that very interesting," said Dr Clive May, Principal Research Fellow at the Howard Florey Institute (The University of Melbourne).

"The sympathetic nerves are the nerves which are stimulated in fight and flight, so they stimulate the heart to work faster and harder.

"So when you're just sitting around there's not a lot happening (nerve-wise), but when you get up to run down the street, suddenly the whole system fires up."

The scientists were also able to accurately measure how, after a heart attack, these sympathetic nerve impulses are known to fire at an elevated level even when at rest.

The constant bombardment of nerve impulses - at close to maximum rate - can cause an irregular heart beat in heart attack patients and even sudden death.

"It's the bodies way of trying to get the heart to pump more blood ... but the problem is the heart is damaged after the heart attack," Dr May said.

In the past the elevated nerve activity could only be inferred from blood tests, and Dr May said an improved understanding of it could help to produce new drugs or techniques designed to control it.

Medical advances also meant that more people were surviving their initial heart attack, adding to the number of people now living with these elevated nerve impulses.

"Because medicine has got so much better, doctors are able to save many of these patients - but they still have damage to their heart," Dr May said.

"Just in Australia there are 300,000 patients with heart failure, and the prognosis for it is worse than many cancers at the moment."

Results of the study are published in the prominent US journal PNAS (Proceedings of the National Academy of Science).