An irregular heartbeat, known as atrial fibrillation, can also lead to ischaemic stroke.

BBC: Andrew Marr: Why do healthy people have strokes?

In 2002 rt-PA was given an EU licence on condition it was used on patients under 80 within three hours of them having an ischaemic stroke.

BBC: Brain

Dr Philip Gorelick, from Michigan State University, said the studies were "major steps forward in the successful treatment of acute ischaemic stroke, and pave the way for new treatment options".

BBC: 'Clot nets' help stroke recovery