Atrial Fibrillation and Stroke:State-of-the-art and future directions

Stroke is a major complication of atrial fibrillation (AF). About 25% of ischaemic stroke are cardio-embolic in origin; AF is the most common cause of those.1 Nonvalvular AF carries a 5-fold increased risk of stroke,2 while AF related to mitral stenosis increases the risk of stroke by 20-fold.3 The attributable risk of stroke for AF increases with age unlike other factors such as hypertension for instance.4When the AF is asymptomatic but detected on a cardiac implantable electronic device (CIED) or a wearable monitor, it is described as being subclinical. It is suspected that subclinical AF might be the cause of cryptogenic strokes (i.e., strokes of unknown aetiology).5 While previous studies showed that atrial high-rate events (AHREs) detected on a CIED were associated with increased risk of stroke,5,6 treating such episodes with anticoagulation has not been shown to reduce the risk of stroke. In fact, anticoagulation in these cases resulted in higher incidence of a composite of death or major bleeding, mainly driven by the increased risk of bleeding.7Not only that AF can cause stroke and vice versa,8 but stroke patients with AF were shown have higher stroke severity and mortality compared to those without.9 The effect of AF on mortality rate was primarily driven by stroke severity.9 The worse clinical and imaging outcome in AF-related strokes was attributed to bigger volumes of more severely hypo-perfused tissues, resulting in larger infarct size and higher risk of haemorrhagic transformation.10In this narrative review article, we provided an overview of the burden of AF and stroke, the complex interplay between the two conditions, as well as the treatment and secondary prevention of stroke in patients with AF. We comprehensively discussed the current evidence and the ongoing conundrums, and highlighted the future directions on the topic