The CHADS2 score for stroke risk stratification in atrial fibrillation – friend or foe?

The risk of stroke in patients with non-valvular atrial fibrillation (NVAF) varies widely depending on patient age and the presence of other risk factors such as hypertension, diabetes mellitus, congestive heart failure or prior stroke or transient ischaemic attack (TIA) (1, 2). Warfarin reduces the risk of stroke by about twothirds when compared to placebo or no treatment, and by about two-fifths when compared to aspirin, but substantially increases major bleeding (2, 3). The most feared complication of warfarin is intracranial bleeding which occurs at the rate of 2–5 per 1,000 patients per year and often results in disability or death (3). Consequently, the decision to use warfarin must balance the benefits of warfarin for stroke prevention against the risk of major bleeding. The goal of stroke prediction models is to help clinicians and patients select the most appropriate antithrombotic therapy for stroke prevention. Because the absolute benefit of warfarin for stroke prevention increases with increasing baseline stroke risk whereas the absolute risk of major bleeding is more constant (3, 4), the balance between benefits and risks of warfarin in individual patients is determined primarily by their baseline untreated stroke risk. In this paper we critically examine the value of the CHADS2 (acronym for recent Congestive heart failure, history of Hypertension, Age≥75 years, Diabetes mellitus, and past history of Stroke or TIA) risk index to estimate stroke risk in patients with NVAF.