The accepted scenario linking atrial fibrillation (AF) and thromboembolism seems straightforward. During AF, thrombus formation is promoted by both blood stasis in poorly contractile atria and a hypercoagulable state, resulting in an extremely high risk of thrombus migration through the systemic circulation. Preventing AF episodes plus treatment with an anticoagulant should therefore dramatically reduce the burden of stroke. One important limitation of such a strategy is the difficulty in recording exhaustively the episode of AF—often clinically silent, cryptogenic AF—and hence identify patients at high risk of stroke. However, through the development of wearable devices such as smart watches and implantable loop recorders (ILRs), which can monitor electrocardiograms (ECGs) over long periods and perform screening for AF, this difficulty can now be overcome.