Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and its prevalence is projected to continuously increase over the next few decades.¹ AF patients usually have several important comorbidities, such as hypertension, diabetes and heart failure, and “lone AF” is becoming uncommon.² The incidence of AF significantly increased when patients have more systemic diseases. In the previous study from Taiwan, the risk of new-onset AF increased from 0.77 per 1000 person-years for patients with a CHADS₂ (congestive heart failure, hypertension, age ≥75, diabetes mellitus, and prior stroke or transient ischemic attack) score of 0 to 34.6 per 1000 person-years for those with a score of 6.³ AF is an important risk factor of ischemic stroke with a worse prognosis and higher recurrence rate compared to that of non-AF related stroke.⁴ The risk of AF-related stroke is not homogenous and mainly depends on the presence or absence of clinical risk factors. Several scoring systems, including CHADS₂ and CHA₂DS₂-VASc (congestive heart failure, hypertension, age ≥75, diabetes mellitus, prior stroke or transient ischemic attack, vascular disease, age 65–74, female) schemes,^5-6 which incorporated clinical important factors have been developed to estimate the risk of stroke and guide anti-thrombotic therapies for AF patients.