Table 3.

Nonvalvular atrial fibrillation risk stratification by CHADS₂ scheme^a and treatment recommendations

CHADS2 score	Risk level	Stroke rate per year	Treatment recommendations based on risk stratification
0	Low	1.0%	Aspirin (75−325 mg/d)
1	Low-moderate	1.5%	Warfarin INR 2−3 or aspirin (75−325 mg/d)b
2a	Moderate	2.5%	Warfarin INR 2−3b
3	High	5.0%	Warfarin INR 2−3c
≥4	Very high	> 7%	Warfarin INR 2−3c

One point for congestive heart failure, hypertension, age over 75 years, or diabetes; Two points for stroke or transient ischemic attack^b.

Abbreviation: INR, international normalized ratio.

^aAll nonvalvular atrial fibrillation patients with prior stroke or transient ischemic attack should be considered high risk and treated with anticoagulants; the CHADS₂ scheme should be applied for primary prevention.

^bConsider patient preferences, bleeding risk, and access to INR monitoring.

^cIf patient is more than 75 years old, an INR target of 1.6 to 2.5 is recommended by some.

Data from Gage BF, Waterman AD, Shannon W, et al. Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation.