The logic behind the device is sound

Eoin Redahan

It is estimated that a high proportion of strokes that occur among this group are caused by a blood clot that forms in a small pouch in the heart's upper left chamber.

The new device effectively seals off this area - known as the left atrial appendage.

Theoretically, this should prevent a blood clot formed in the pouch from travelling to the brain and causing a stroke.

German researchers used the device to successfully seal off the area in the hearts of 15 patients with chronic atrial fibrillation.

They used a catheter to place the device at the mouth of the appendage.

Pointless pouch

Dr Horst Sievert, a senior consultant at the Cardiovascular Center of Bethanien Hospital in Frankfurt, said: "The left atrial appendage has no purpose; no one needs it.

"Its only function is to form clots. It can be blocked with no disadvantage to the patient."

Implanting a mechanical device to block the left atrial appendage can be done safely and with relative ease

Dr Horst Sievert

The blocking device is a self-expanding metal cage made of nitinol that pops open as the metal warms up inside the body.

The cage is covered with a membrane, which both blocks the atrial appendage and allows normal tissue to grow into the device.

Tiny spikes attached to the alloy cage that protrude through its covering anchor the device in place.

Dr Sievert said that after six months none of the patients had suffered a stroke. Neither had there been any complications.

Drug therapy

The anti-clotting drug warfarin is used to prevent strokes in atrial fibrillation patients.

However, the drug can be difficult to control and many patients cannot take it.

Dr Sievert stressed that more work was needed to show that the therapy will prevent strokes.

He said: "This initial study supports the concept that implanting a mechanical device to block the left atrial appendage can be done safely and with relative ease.

"It may became a valuable alternative for patients with chronic, non-rheumatic AF in whom standard anticoagulation therapy is contraindicated or poorly tolerated."

'Extraordinary'

Eoin Redahan, of the Stroke Association, told BBC News Online that the research was "extraordinary".

He said: "It certainly takes a different approach to the problem caused by atrial fibrillation.

"Although the numbers involved were small, the logic behind the device is sound.

"Atrial fibrillation is a major risk factor for stroke and warfarin is the main way to counteract this risk.

"However it is a very difficult medication to give the correct dosage and any other system that might help counteract the effects is to be welcomed.

"We will watch further trials with interest."

The research is published in Circulation: Journal of the American Heart Association.