Up to 40% of ischaemic strokes have no known cause, and thus are classified as 'cryptogenic stroke'. Some of these strokes may be caused by atrial fibrillation (AF), an abnormal heart rhythm that can lead to blood clots from the heart travelling up into the brain. In today's podcast, Prof Vincent Thijs is back, talking about how to detect AF in stroke patients, and what we can do about cryptogenic stroke.