Atrial fibrillation and stroke: epidemiology.

The statistics for AFib are impressive. (online video available at: http://education.amjmed.com/video.php?event_id=445&stage_id=5&vcs=1). The principal risk with AFib, stroke or thrombotic embolism, is increased 5-fold in some series; AFib accounts for ≥15% of all strokes in the United States, 36% of strokes for individuals aged >80, and up to 20% of cryptogenic strokes, which means >100,000-125,000 embolic strokes per year, of which >20% are fatal. Patients with ischemic stroke and AFib are significantly (P<.0005) more likely to be chronically disabled, bedridden, and to require constant nursing care, particularly older patients (≥85 years). Prevention of these thromboembolic outcomes requires prophylactic anticoagulation therapy. The "gold standard" for anticoagulation has been warfarin, despite its well-known side effects and adherence challenges for patients. The recent approvals of several new, novel oral anticoagulation (NOAC) agents, however, presents physicians with a benefit/risk profile that represents an important advance over warfarin prophylaxis. The principal risk with all oral anticoagulants is bleeding. An important misconception about warfarin is that if anticoagulated patients bleed, the risk can be quickly reversed, but most trial experience has found that warfarin reversal requires 24 hours to halve the INR value. Reversal of anticoagulation with the NOACs is unproven at present; possible approaches are presented in this review, but since the NOACs have both rapid onsets of action and short biologic half-lives, they do not present the same reversal challenges as warfarin. Finally, physicians must be aware of thromboembolic risk assessment. The principal risk assessment scores are CHADS2, updated with the more recent CHA2DS2-VASc to provide more accurate assessment of low-risk patients; this review concludes with a novel flow-chart showing physicians how the CHADS2/CHA2DS2-VASc scoring systems can be used.