American doctors have used lasers to "vapourise" blood clots in stroke victims.

The experimental treatment was carried out by a team at the Oregon Stroke Center in Portland.

Stroke, in 80% of patients, is caused by a blood clot.

Five patients who were identified as having a clot-caused stroke had a catheter - equipped with a laser - threaded through their carotid blood vessels until it reached the exact location of the clot.

Laser drawn to red

Medical staff were able to see where the catheter was using an aniogram.

They then moved the laser to within 1cm of the clot and activated it.

Light from the laser is drawn only to red - the colour of clots - rather than white, the colour of the vessel surrounding the clot.

Currently, acute treatment for stroke caused by blood clots involves the administration of clot-dissolving drugs.

The advantage of laser surgery is that the clot can be eliminated within minutes rather than hours.

The Oregon Stroke Center team found that the patients studied had to be given laser treatment within 8 to 24 hours of a stroke, depending on its location.

Team leader Dr Wayne Clark told the American Stroke Association's 25th annual conference: "It looks very promising. But at this point, we're mainly studying safety. We have achieved complete vessel re-opening in some patients, while in others, treatment was not possible due to difficulties getting to the clot with the laser-tipped catheter."

Dr Clark said that mechanical clot removal - either with lasers or clot suction devices - could be the next wave of acute stroke treatment.

He added: "We don't know which device or which technique will be the answer, but I think it is reasonable to say that five years from now, mechanical clot disruption will be a major factor in the treatment of acute stroke, particularly in patients with larger strokes, this type of treatment could be useful."