CHADS2 score

For other uses, see Chad (disambiguation).

	Condition	Points
C	Congestive heart failure	1
H	Hypertension: blood pressure consistently above 140/90 mmHg (or treated hypertension on medication)	1
A	Age ≥75 years	1
D	Diabetes mellitus	1
S2	Prior Stroke or TIA	2

The CHADS₂ score is a clinical prediction rule for estimating the risk of stroke in patients with non-rheumatic atrial fibrillation (AF), a common and serious heart arrhythmia associated with thromboembolic stroke. It is used to determine whether or not treatment is required with anticoagulation therapy or antiplatelet therapy,^[1] since AF can cause stasis of blood in the upper heart chambers, leading to the formation of a mural thrombus that can dislodge into the blood flow, reach the brain, cut off supply to the brain, and cause a stroke. A high CHADS₂ score corresponds to a greater risk of stroke, while a low CHADS₂ score corresponds to a lower risk of stroke. The CHADS₂ score is simple and has been validated by many studies.^[2]

The CHADS₂ scoring table is shown above:^[3] adding together the points that correspond to the conditions that are present results in the CHADS₂ score, that is used to estimate stroke risk.

Stroke risk assessment, and antithrombotic therapy

Annual Stroke Risk^[2]

CHADS2 Score	Stroke Risk %	95% CI
0	1.9	1.2–3.0
1	2.8	2.0–3.8
2	4.0	3.1–5.1
3	5.9	4.6–7.3
4	8.5	6.3–11.1
5	12.5	8.2–17.5
6	18.2	10.5–27.4

According to the findings of the initial validation study, the risk of stroke as a percentage per year for the CHADS₂ score is shown in the Table.

The CHADS₂ score does not include some common stroke risk factors and its various pros/cons have been carefully discussed.^[4] Nonetheless, this score is simple and thus it has become widely used.

To complement the CHADS₂ score, by the inclusion of additional 'stroke risk modifier' risk factors, the CHA2DS2-VASc score has been proposed.^[5] These additional non-major stroke risk factors include age 65-74, female gender and vascular disease. In the CHA2DS2-VASc score score, 'age 75 and above' also has extra weight, with 2 points.

The CHA2DS2-VASc score has been used in the new European Society of Cardiology guidelines for the management of atrial fibrillation.^[6][7]

The European Society of Cardiology (ESC) guidelines recommend that if the patient has a CHADS₂ score of 2 and above, oral anticoagulation therapy (OAC) such as warfarin (target INR of 2-3) or one of the new OAC drugs, such as dabigatran) should be prescribed.

If the CHADS₂ score is 0-1, other stroke risk modifiers could be considered: (i) If there are 2 or more risk factors (essentially a CHA2DS2-VASc score score of 2 or more), OAC is recommended; and (ii) If there is 1 risk factor (essentially a CHA2DS2-VASc score score=1), antithrombotic therapy with OAC or aspirin (OAC preferred) is recommended, and patient values and preferences should be considered.

A CHA2DS2-VASc score score=0 corresponds to a 'truly low risk,’^[8][9] and thus the recommendation is to prescribe either aspirin or no antithrombotic therapy, but 'no antithrombotic therapy' is preferred.^[10]

Stroke risk assessment should always include an assessment of bleeding risk. This can be done using validated bleeding risk scores, such as the HEMORR₂HAGES or HAS-BLED scores. The latter is recommended in the ESC and Canadian guidelines.^[11] If the patient is taking warfarin, then knowledge of INR control is needed to assess the 'labile INR' criterion in HAS-BLED; otherwise for a non-warfarin patient, this scores zero.

Anticoagulation

Score	Risk	Anticoagulation Therapy	Considerations
0	Low	None or Aspirin	Aspirin daily
1	Moderate	Aspirin or Warfarin	Aspirin daily or raise INR to 2.0-3.0, depending on patient preference
2 or greater	Moderate or High	Warfarin	Raise INR to 2.0-3.0, unless contraindicated

Treatment strategies recommended based on the CHADS₂ score are shown in the table.^[1][2]

How the treatment recommendations based on the CHADS₂ score are modified by considering additional 'stroke risk modifier' risk factors using the CHA2DS2-VASc score, see ESC guideline recommendations, which recommend the management as shown in the following table:

CHA₂DS₂-VASc

	Condition	Points
C	Congestive heart failure (or Left ventricular systolic dysfunction)	1
H	Hypertension: blood pressure consistently above 140/90 mmHg (or treated hypertension on medication)	1
A2	Age ≥75 years	2
D	Diabetes Mellitus	1
S2	Prior Stroke or TIA or thromboembolism	2
V	Vascular disease (eg. peripheral artery disease, myocardial infarction, aortic plaque)	1
A	Age 65-74 years	1
Sc	Sex category (i.e. female gender)	1

The CHA₂DS₂-VASc score is a refinement of CHADS₂ score and extends the latter by including additional common stroke risk factors, as discussed below.

The maximum CHADS₂ score is 6, whilst the maximum CHA₂DS₂-VASc score is 9.

Anticoagulation

Score	Risk	Anticoagulation Therapy	Considerations
0	Low	No antithrombotic therapy (or Aspirin)	No antithrombotic therapy (or Aspirin 75-325mg daily)
1	Moderate	Oral anticoagulant (or Aspirin)	Oral anticoagulant, either new oral anticoagulant drug eg dabigatran or well controlled warfarin at INR 2.0-3.0 (or Aspirin 75-325mg daily, depending on factors such as patient preference)
2 or greater	High	Oral anticoagulant	Oral anticoagulant, using either a new oral anticoagulant drug (eg rivaroxaban or dabigatran) or well controlled warfarin at INR 2.0-3.0

Based on the ESC guidelines on Atrial Fibrillation, oral anticoagulation is recommended or preferred for patients with one or more stroke risk factors (ie. a CHA₂DS₂-VASc score of 1 and above). This is consistent with a recent decision analysis model showing how the 'tipping point' on the decision to anticoagulate has changed with the availability of new 'safer' OAC drugs.^[12][13]

References

1. ^ ^{a b} Gage BF, van Walraven C, Pearce L, et al. (2004). "Selecting patients with atrial fibrillation for anticoagulation: stroke risk stratification in patients taking aspirin". Circulation 110 (16): 2287–92. doi:10.1161/01.CIR.0000145172.55640.93. PMID 15477396. http://circ.ahajournals.org/cgi/content/full/110/16/2287. 
2. ^ ^{a b c} Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ (2001). "Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation". JAMA 285 (22): 2864–70. doi:10.1001/jama.285.22.2864. PMID 11401607. http://jama.ama-assn.org/cgi/content/full/285/22/2864. 
3. ^ "Risk of Stroke with AF". VA Palo Alto Medical Center and at Stanford University: the Sportsmedicine Program and the Cardiomyopathy Clinic. http://www.cardiology.org/tools/risk_of_stroke_AF.html. Retrieved 2007-09-14. 
4. ^ Karthikeyan G, Eikelboom JW. The CHADS2 score for stroke risk stratification in atrial fibrillation--friend or foe? Thromb Haemost. 2010 Jul 5;104(1):45-8.
5. ^ Lip GY, Nieuwlaat R, Pisters R, Lane DA, Crijns HJ. Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach: the euro heart survey on atrial fibrillation. Chest. 2010 Feb;137(2):263-72.
6. ^ European Heart Rhythm Association; European Association for Cardio-Thoracic Surgery, Camm AJ, Kirchhof P, Lip GY, Schotten U, Savelieva I, Ernst S, Van Gelder IC, Al-Attar N, Hindricks G, Prendergast B, Heidbuchel H, Alfieri O, Angelini A, Atar D, Colonna P, De Caterina R, De Sutter J, Goette A, Gorenek B, Heldal M, Hohloser SH, Kolh P, Le Heuzey JY, Ponikowski P, Rutten FH. Guidelines for the management of atrial fibrillation: the Task Force for the Management of Atrial Fibrillation of the European Society of Cardiology (ESC). Eur Heart J. 2010 Oct;31(19):2369-429.
7. ^ http://www.escardio.org/guidelines-surveys/esc-guidelines/Pages/atrial-fibrillation.aspx
8. ^ Olesen JB, Lip GY, Hansen ML, Hansen PR, Tolstrup JS, Lindhardsen J, Selmer C, Ahlehoff O, Olsen AM, Gislason GH, Torp-Pedersen C. Validation of risk stratification schemes for predicting stroke and thromboembolism in patients with atrial fibrillation: nationwide cohort study. BMJ. 2011 Jan 31;342:d124. doi: 10.1136/bmj.d124.
9. ^ Van Staa TP, Setakis E, Di Tanna GL, Lane DA, Lip GY (October 2010). "A comparison of risk stratification schema for stroke in 79884 atrial fibrillation patients in general practice.". J Thromb Haemost.: no. doi:10.1111/j.1538-7836.2010.04085.x. PMID 21029359. 
10. ^ Lip GY, Halperin JL. (Jun 2010). "Improving stroke risk stratification in atrial fibrillation". Am J Med. 123 (6): 484–8. doi:10.1016/j.amjmed.2009.12.013. PMID 20569748. 
11. ^ Cairns JA, Connolly S, McMurtry S, Stephenson M, Talajic M; CCS Atrial Fibrillation Guidelines Committee. Canadian Cardiovascular Society atrial fibrillation guidelines 2010: prevention of stroke and systemic thromboembolism in atrial fibrillation and flutter. Can J Cardiol. 2011 Jan-Feb;27(1):74-90. PubMed PMID: 21329865.
12. ^ Eckman MH, Singer DE, Rosand J, Greenberg SM. Moving the tipping point: the decision to anticoagulate patients with atrial fibrillation. Circ Cardiovasc Qual Outcomes. 2011 Jan 1;4(1):14-21.
13. ^ http://www.escardio.org/guidelines-surveys/esc-guidelines/Pages/atrial-fibrillation.aspx