Atrial fibrillation is the most common arrhythmia and the likelihood of having it increases with age. If left untreated it can lead to heart failure and is a significant risk factor for stroke but risk can be greatly reduced with oral anticoagulation. Many people with AF remain asymptomatic, but the risk of stroke remains the same. Simple screening methods will help detect those at risk. Many of those with a diagnosis and at high risk of stroke remain untreated. This two-part series aims to raise awareness of the importance of early detection and appropriate treatment. Part one discusses the complications linked to AF and explores the nurse's role in screening; part two will look at management.