Key to cardiac arrests?

An international team has also found why many common drugs, including antibiotics and antipsychotics, can cause a potentially fatal abnormal heart rhythm, a finding which may pave the way for better drugs for cardiac arrests.

It is estimated around 40-50 per cent of all drugs in development will block one of the main `channels` that carries electricity in the heart and could cause heart rhythm problems called cardiac arrhythmias. Most sudden cardiac deaths are caused by cardiac arrhythmias1.

In the research, the scientists, led by the Victor Chang Institute in Sydney, have discovered a key clue as to why this happens, by understanding how the "gates", which effectively "open" and "close" the channel, operate.

"Just like a set of metal wires that carry electricity to light up our streets, our body has a series of channels that carry tiny charged particles called ions, into and out of cells, to trigger a heartbeat," said Prof Jamie Vandenberg, who led the team.

"Depending on the position of these gates, many common drugs bind, or attach themselves to these channels, blocking the ions from passing through. This causes what we call Long QT syndrome, where the length of the heart beat is longer than usual, which increases the risk of arrhythmia," he added.

The group of drugs most commonly associated with this side effect are anti-psychotic drugs, taken by patients with schizophrenia and other psychiatric disorders. Patients taking these drugs are up to three times more likely to die of sudden cardiac death due to an abnormal heart rhythm.