Atrial fibrillation (AF) is the most common type of cardiac arrhythmia and is associated with significant mortality and morbidity from stroke, thromboembolism, and related cardiovascular conditions. While the risk of stroke for AF patients as a whole tends to be greater than the general population; within the AF patient population, the risk of stroke is modified by the presence or absence of additional risk factors such as age, comorbid conditions, and prior stroke history.