New drug Multaq could dramatically reduce heart rhythm disorders, which can cause breathlessness and prove deadly

Tens of thousands of strokes could be prevented each year in patients with a common heart rhythm disorder, say researchers.

Findings from the largest trial of its kind show that Multaq reduced the chances of stroke by more than a third in those with atrial fibrillation.

The drug has already been shown to cut heart deaths by 30 per cent and the risk of hospital treatment and deaths from any cause by 25 per cent in earlier results from the same trial.

But findings on strokes released yesterday are highly significant because atrial fibrillation, known as AF, accounts for about 30,000 out of 150,000 strokes each year in the UK. Problems with the speed or rhythm of the heartbeat are known as arrhythmia.

Multaq is an anti-arrhythmic drug and is being hailed as the first advance in 20 years in tackling AF and the separate condition of atrial flutter which affects almost a million Britons.

Many AF patients need long-term drug treatment such as blood thinners and anti-clotting agents to stabilise a fast and erratic heartbeat-that can cause serious complications such as angina and heart failure.

In cases of AF the upper chambers of the heart are out of rhythm, which can result in the heart beating at a rate of 150 to 170 beats a minute rather than the normal range of 70 to 90.

The condition generates tiny blood clots which are sent around the body and can trigger a stroke. More than 4,500 patients with AF from 33 countries, including the UK, took part in a trial called Athena to investigate the effectiveness of Multaq, also known as dronedarone, on top of standard therapy.

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Half of the patients, who were all at high risk of suffering heart complications and stroke, were given a dummy treatment or placebo.

After treatment lasting at least a year, the researchers found a 34 per cent cut in risk of stroke compared with those taking placebo.

The most frequently reported side-effects were gastrointestinal, such as tummy upset. This was seen among one in four users.

The findings were presented at the European Society of Cardiology congress in Munich.

Professor Stuart Connolly, of McMaster University, Hamilton, Canada, who led the study, said it was a landmark trial. 'It is the first time that an anti-arrhythmic drug has shown a significant impact on cardiovascular outcomes,' he said.

'As stroke is one of the leading complications of atrial fibrillation, and a major cause of death and disability, these results demonstrate the unique profile of Multaq beyond its pure rhythm and rate-controlling effects.'

Dr Pete Coleman of the Stroke Association said: 'This is very encouraging.'