Which blood-thinning agents are used to reduce the risk of stroke in atrial fibrillation (Afib) (AF) lasting longer than 24 hours?

Updated: Apr 09, 2019
  • Author: Lawrence Rosenthal, MD, PhD, FACC, FHRS; Chief Editor: Jeffrey N Rottman, MD  more...
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Answer

The risk of stroke from AF that lasts longer than 24 hours is a major concern and is usually addressed by prescribing a blood thinner (warfarin, dabigatran, rivaroxaban, apixaban, or edoxaban). The CHADS2 prognostic scoring system was originally derived to estimate the risk of ischemic stroke in patients with AF. A higher CHADS2 score implies a higher risk of ischemic stroke; in older guidelines, a CHADS2 score of 2 or greater was considered an indication for using blood thinners. [40]  However, the CHADS2 score appears to underestimate the risk of embolic stroke in patients older than 75 years. [41]  Furthermore the CHADS2 score does not include some of the other risk factors associated with ischemic stroke in AF patients, such as female sex and vascular disease.

An analysis of the AFNET (Central Registry of the German Competence NETwork on Atrial Fibrillation) registry of 8847 patients with nonvalvular AF indicated that the CHA2 DS2-VASc score is more sensitive than the CHADS2 score for risk stratification of thromboembolic events (ischemic stroke, transient ischemic attack [TIA], systemic embolism), particularly in patients with a CHADS2 score of 0 or 1 who would have otherwise not received prescribed anticoagulation therapy on the basis of previous guidelines. [42, 43]  However, CHA2 DS2-VAScc scoring—which adds age 65-74 years, arterial disease, and female sex as stroke risk factors to the CHADS2 score [43] —placed 30.3% of those classified as CHADS2 0 or 1 into CHA2 DS2-VASc 1 or 2 and higher, groups in which oral anticoagulation is now recommended.

In another investigation of over 47,000 participants with a CHADS2  score of 0 to 1 who were not on anticoagulation therapy, Olesen et al reported a serial increase in the risk of stroke/thromboembolism with an increase in CHA2 DS2-VASc score. [44] Furthermore, a regression model with the CHA2 DS2-VASc score showed higher discrimination for predicting stroke than the model with the CHADS2 score. [44]


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