Essence of this Article
Atrial fibrillation (AF) is the most common form of cardiac arrhythmia. Disorganized atrial contraction, leading to blood stasis and low shear conditions, encourages the formation of fibrin-rich thrombi within the left atrium and left atrial appendage. Embolization of atrial thrombi can then result in ischaemic stroke. Other factors such as heart failure, diabetes and previous stroke increase the risk of stroke in patients with AF.
Atrial fibrillation-related thrombi
AF, the most common form of cardiac arrhythmia, is associated with the formation of ‘venous-type’ fibrin-rich thrombi. AF involves a lack of organized atrial contraction. By reducing the movement of blood, AF creates stagnant blood and low shear conditions, which encourage the formation of thrombi in the left atrium or left atrial appendage of the heart.36 These thrombi can break free and embolize to block a cerebral artery, causing ischaemic injury. Consequently, AF is associated with a major risk of ischaemic stroke.
- Heart failure
- History of hypertension
- Prior history of stroke or transient ischaemic attack (TIA)
Several scoring systems are available to help clinicians estimate the stroke risk in AF. One popular, validated risk assessment tool is ‘CHADS2’. This system assigns single points for Congestive Heart failure, hypertension, Age over 75 and Diabetes, and two points for history of Stroke or TIA. A total score over 2 is considered high risk.48, 49 More recently, the ‘CHA2DS2-VASc’ scoring system has been proposed in guidelines as an improvement on the CHADS2 score for identification of patients with AF who require anticoagulation, and those who do not.50, 51
Incidence and prevalence of AF
AF is the most common sustained arrhythmia seen in clinical practice occurring in 1–2% of the general population.52 AF has been reported as affecting an estimated 6 million people in the European Union and at least 2.7 million people in the United States in 2010.52, 53
Ischaemic stroke, resulting from an embolism, is a serious complication of AF.49 The incidence of stroke in patients with non-valvular AF (i.e. AF not caused by damage to the mitral valve) is between twofold and sevenfold greater than in the general population. For patients with AF caused by valvular disease, the risk of stroke increases 17-fold.558