CHADS2 Score for Stroke Risk Assessment in Atrial Fibrillation 

Updated: Apr 19, 2017
  • Author: Tarek Ajam, MD, MS; more...
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CHADS2 and CHA2DS2-VASc Score for Stroke Risk Assessment in Atrial Fibrillation

Atrial fibrillation (AF) is a cardiac arrhythmia with the potential to cause thromboembolism. Studies suggest that AF increases the risk of stroke five-fold. [1]  Thus, it is important to determine which patients with AF may benefit from oral anticoagulant (OAC) and possibly aspirin therapy to reduce the risk of stroke. OACs used in this setting include the following medications for stroke preventions in atiral fibrillation:

  • Warfarin, with a goal International Normalized Ratio (INR) of 2-3 and percent time in therapeutic INR (TTR) remains ≥ 70%
  • Dabigatran
  • Rivaroxaban
  • Apixaban
  • Edoxaban

First published in 2001, the CHADS2 score (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, stroke [double weight]) was developed to more accurately predict the risk of stroke in patients with nonrheumatic AF. [2]  The index was derived by combining risk factors from prior studies and then testing their validity in a cohort of 1,773 Medicare-aged patients over 2,121 patient years. [3, 4]  Valvular AF which is not represented by this study includes the presence of moderate to severe mitral stenosis or the presence of mechanical prosthetic valve.

See Tables 1 and 2, below. 

Table 1. CHADS2 Score: Stroke Risk Assessment in Atrial Fibrillation (Open Table in a new window)

Score CHADS2 Risk Criteria
1 point Congestive heart failure
1 point Hypertension
1 point Age ≥ 75 years
1 point Diabetes mellitus
2 points Stroke/transient ischemic attack

Table 2. CHADS2  Score and Corresponding Annual Stroke Risk (Open Table in a new window)

CHADS2 Score Adjusted Stroke Risk (%)
0 1.9
1 2.8
2 4
3 5.9
4 8.5
5 12.5
6 18.2

The above adjusted stroke rates are based on data for hospitalized patients with AF and were published in 2001. [2]  Actual stroke rates in contemporary nonhospitalized cohorts might vary from these estimates since stroke rates are decreasing [5]

See also Medscape's Atrial Fibrillation CHADS2 Score for Stroke Risk calculator.

Although simple, the CHADS2 score does not include many common stroke risk factors, and its limitations have been highlighted by its non-inclusion of common stroke risk factors. Even patients classified as low risk by CHADS2 in its original validation study have a stroke rate of 1.9% per year, which is close to the criterion of a cardiovascular event rate of 20% over 10 years for primary prevention strategies (ie, statin therapy). [6, 7]

Consequently, CHADS2 was expanded to include three additional independent risk factors: vascular disease (coronary artery disease, peripheral artery disease, aortic atherosclerosis), age 65-74 years, and female sex. [8, 9, 10] This new, more inclusive scoring system is the CHA2DS2-VASc score. [11]

The CHA2DS2-VASc score better discriminated stroke risk in nonvalvular AF subjects with a baseline CHADS2 score of 0 to 1; its improved predictive ability was demonstrated in a nationwide Danish registry from 1997 to 2008. [12]  In a Swedish population with nonvalvular AF, [13] women had a moderately increased stroke risk compared with men. However, women younger than 65 years without other AF risk factors had a low risk for stroke, and it was concluded that those patients did not require OAC prophylaxis. 

The 2016 European Society of Cardiology (ESC) guidelines recommend using the CHA2DS2-VASc score to estimate stroke risk in AF patients and to start OACs in men with a score of 1 or higher and women with a score of 2 or higher. [14]  The 2014 American Heart Association/ American College of Cardiology/ Heart Rhythm Society (AHA/ACC/HRS) guidelines also recommend the CHA2DS2-VASc score for the assessment of stroke risk in paitents with nonvalvular AF. Consideration of OAC prophylaxis is recommended for patients with a score of 1 and OAC use is a definite recommendation for patients with a score of 2 or greater and for those with a history of stroke or transient ischemic attack. [15]  

Use of the CHA2DS2-VASc score to determine stroke risk in patients having cardiac surgery independent of AF has been advocated. [18] Stroke prevention versus bleeding risk in AF can be addressed if the HAS-BLED (Hypertension, Abnormal renal/liver function, Stroke, Bleeding history or predisposition, Labile INR, Elderly, Drugs/alcohol concomitantly) score is also calculated with the CHA2DS2-VASc score.

See Tables 3, 4, and 5, below. See also Medscape's Atrial Fibrillation CHA2DS2-VASc Score for Stroke Risk calculator.

Table 3. CHA2DS2-VASc Score and Risk Criteria (Open Table in a new window)

Score CHA2DS2-VASc Risk Criteria
1 point Congestive heart failure
1 point Hypertension
2 points Age ≥75 years
1 point Diabetes mellitus
2 points Stroke/Transient Ischemic Attack/Thromboembolic event
1 point Vascular disease (prior MI, PAD, or aortic plaque)
1 point Age 65 to 74 years
1 point Sex category (ie, female sex)

Table 4. CHA2DS2-VASc Score and Corresponding Annual Stroke Risk (Open Table in a new window)

CHA2DS2-VASc Score Adjusted Stroke Risk, (% per year)
0 0
1 1.3
2 2.2
3 3.2
4 4.0
5 6.7
6 9.8
7 9.6
8 6.7
9 15.2

Adjusted stroke rate scores are based on data from Lip and colleagues. [5, 8, 16, 17]  The actual rates of stroke in contemporary cohorts may vary from these estimates.

Table 5. Treatment Recommendations Based on CHA2DS2-VASc Score [15] (Open Table in a new window)

CHA2DS2-VASc Score Recommendation
0 None
1 None or aspirin or OAC
2 or more OAC