Oral Antithrombotic Agents for the Prevention of Stroke in Nonvalvular Atrial Fibrillation

Abstract

T he rate of stroke among adults with atrial fibrilla- tion (AF) varies widely, ranging between 1% and 20% annually (mean 4.5% per year) depending on comorbidities and a patient's history of prior cerebrovascular events. 1 Stratification of stroke risk is important, because the major risk of antithrombotic medications used to lower the incidence of AF-related stroke is bleeding.2][3] The advent of several new antithrombotic agents offers alternatives to warfarin and may lower the threshold for thromboembolic risk for initiating therapy in patients with AF.In this update to the American Heart Association/ American Stroke Association (AHA/ASA) "Guidelines for the Primary Prevention of Stroke" 4 and the prevention of stroke in patients with stroke or transient ischemic attack (TIA), 5 we review recent trials testing the safety and efficacy of a thrombin inhibitor (dabigatran) and 2 factor Xa inhibitors (rivaroxaban and apixaban) in preventing stroke in patients with AF, and we revise management recommendations. 4,5Recommendations follow the AHA's and the American College of Cardiology's methods of classifying the level of certainty of the treatment effect and the class of evidence (Table 1). Summary of Current AHA/ASA Guidelines for Vitamin K Antagonists/Antithrombotics inPatients With AF Risk StratificationThe absolute risk of stroke varies 20-fold among AF patients according to age and associated vascular comorbidities.7][8] These, however, can yield differing results. 9Current AHA guidelines use the CHADS 2 stratification scheme 7 (CHADS 2 is an acronym for Congestive heart failure, Hypertension, Age ≥75 years, Diabetes mellitus, and prior Stroke or TIA).The CHADS 2 score was derived from independent predictors of stroke risk in patients with nonvalvular AF. 7 The score assigns 1 point each for congestive heart failure, hypertension, age ≥75 years, and diabetes mellitus and 2 points for prior stroke or TIA. 7The score was validated in a large cohort study and in clinical trials. 6,10For Oral Antithrombotic Agents for the Prevention of Stroke in Nonvalvular Atrial Fibrillation

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