Bay?s? syndrome refers to the association between interatrial block and supraventricular arrhythmias'mainly the occurrence of atrial fibrillation. It is also a risk factor for cardio-embolic stroke. Rapid recognition by analyzing characteristic patterns in the surface ECG will help the physician to closely monitor the patient for atrial fibrillation and decide on anticoagulation therapy if the clinical risk of stroke is increased.Interatrial blocks...