CHADS2 score

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CHADS2 Score Microchapters

Overview

Calculation of the CHADS2 Score

Interpretation of the CHADS2 Score

Antithrombotic Therapy Based on the CHADS2 Score

Use of the CHADS2 Score in Populations without Atrial Fibrillation

Description of the Original Study

Strengths

Limitations

CHA2DS2-VASc

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and Keywords: CHADS score

Overview

CHADS2 score is a clinical prediction rule for the estimation of the risk of stroke among patients with non-rheumatic atrial fibrillation (AF), a common and serious cardiac arrhythmia associated with an increased risk of thromboembolic stroke. AF can cause stasis of blood in the atria, leading to the formation of a mural thrombus that can dislodge into the blood flow, reach the brain, and cause a stroke. CHADS2 score is used to assess the risk of stroke and determine whether or not antithrombotic therapy is required with either anticoagulants therapy or antiplatelets for the prevention of thromboembolism.[1] 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 was validated by a study on non-rheumatic AF patients aged 65 to 95 who were not prescribed the anticoagulant warfarin.[2]

Calculation of the CHADS2 Score

The CHADS2 risk score is calculated by adding the points assigned to the different variables shown below.[2]

Variable 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 transient ischemic attack (TIA)
2

Interpretation of the CHADS2 Score

Shown below is the probability of the annual stroke risk by the corresponding CHADS2 score value.[2]

CHADS2 Score Stroke Risk % 95% Confidence Interval
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

Antithrombotic Therapy Based on the CHADS2 Score

Shown below is a table depicting the recommended treatment strategies with anticoagulation or antiplatelets based on the value of CHADS2 score as advised by the 2011 ACCF/AHA/HRS focused updates incorporated into the ACC/AHA/ESC 2006 Guidelines for the management of patients with atrial fibrillation[3][1][2]

Score Risk Anticoagulation Therapy Considerations
0 Low Aspirin Aspirin daily
1 Moderate Aspirin or Warfarin Aspirin daily or INR to 2.0-3.0, depending on factors such as patient preference
2 or greater Moderate or High Warfarin INR to 2.0-3.0, unless contraindicated (e.g. clinically significant GI bleeding, inability to obtain regular INR screening)

The 2010 Task Force for the Management of Atrial Fibrillation of the European Society of Cardiology (ESC) recommend that if the patient has a CHADS2 score of 2 and above, oral anticoagulation (OAC) therapy is recommended. OAC options include warfarin with an INR target of 2-3 or dabigatran.[4]

In order to improve upon the prognostic utility of the CHADS2 score and to incorporate additional stroke risk factors, the CHA2DS2-VASc score has been proposed.[5]. Click here to read more about the CHA2DS2-VASc score.

Use of the CHADS2 Score in Populations without Atrial Fibrillation

The CHADS2 score has been shown to also predict the risk of ischemic stroke among those patients who do not have atrial fibrillation.[6] It should be noted however, that the CHADS2 Score has not been used to guide the selection of anticoagulation therapy in patients without atrial fibrillation.

Description of the Original Study

The CHADS2 index was developed by the Gage et al., published in the Journal of the American Medical Association in June 2001, with the objective of assessing the predictive value of classification schemes that estimate stroke risk in patients with AF. To develop the index, two existing classification schemes from the Atrial Fibrillation Investigators (AFI), and the Stroke Prevention and Atrial Fibrillation investigators (SPAF) were combined, and all 3 classification schemes were validated. 1 point each was assigned for the presence of congestive heart failure, hypertension, age 75 and older, and diabetes mellitus, and 2 points were assigned for history of stroke or transient ischemic attack. Data was obtained from peer review organizations representing 7 different states to create a National Registry of Atrial Fibrillation consisting of 1733 Medicare beneficiaries aged 65 to 95 years who had non-rheumatic AF and were not prescribed warfarin at discharge. The outcome measured was the hospitalization for ischemic stroke, which was determined by medicare claims data. The 1733 patients were followed for a median of 1.2 years. The results were as follows;

  • During the 2121 patient-years of follow up, 94 patients were re-admitted for an ischemic event; 73 of these patients were admitted for stroke, and 23 patients for transient cerebral ischemia.
  • The stroke rate was lowest amongst the 120 patients who had a CHADS2 score of 0.
  • The stroke rate increased by a factor of 1.5 (95% CI, 1.3-1.7) for each 1 point increase in the CHADS2 score.
  • Aspirin was associated with a hazard rate of 0.80 (95% CI, 0.5-1.3) corresponding to a nonsignificant 20% RR reduction in the rate of stroke (p=0.27)
  • Compared to the schemes developed by the AFI and SPAF, the CHADS2 index was the most accurate predictor of stroke with a c-statistic of 0.82 (95% CI, 0.80-0.84).

Strengths

  • The CHADS2 study used chart reviews rather than ICD-9-CM claims to document the presence of AF and to identify stroke risk factors.
  • The chart reviews included patients who received aspirin after being discharged from the hospital, enabling adjustment for the use of aspirin in the calculation of the CHADS2 specific stroke rate.
  • The cohort of persons used in the study were Medicare beneficiaries from 7 different states, and all geographic regions of the United States were represented.
  • As the CHADS2 study used Medicare beneficiaries who were recently hospitalized rather than healthier individuals, it is thought that CHADS2 should be generalizable to frail and elderly individuals

Limitations

  • The CHADS2 score has various limitations, which have been debated.[7] Notably, many stroke risk factors have not been included, and whilst simple, the score has only modest predictive value for thromboembolism.
  • The CHADS2 score may underestimate the risk of stroke in those patients over the age of 75 years. For this reason, some authors have advocated the use of anticoagulation among patients who are over the age of 75 years if there are no contraindications.[8]
  • When compared to data from clinical trials from The Stroke Prevention and Atrial Fibrillation investigators (SPAF) and the Atrial Fibrillation Investigators (AFI), the CHADS2 study used participants who were older and sicker. The CHADS2 study was based on the SPAF and AFI schemes; therefore, the study may have performed better if it was used in a younger cohort of patients.
  • A single chart review was used to measure the stroke risk factors, and therefore the study was unable to capture new stroke risk factors that may have developed in the cohort participants.
  • The study only looked at patients who were hospitalized and were not prescribed warfarin.
  • As Medicare claims were used to ascertain the number of ischemic events, there was no way to verify these events.
  • The 20% risk reduction of stroke with aspirin administration was not statistically significant in this study (however there is clinical significance when the study is combined with other research).
  • While the CHADS2 score provides prognostic information regarding the natural history of non-valvular AF in the absence of warfarin therapy, it should be noted that warfarin therapy also has an associated stroke risk (particularly hemorrhagic stroke) and a risk of major bleeding, and these considerations were taken into account in the development of the recommendations in the next section.[9]

CHA2DS2-VASc

Main article: CHA2DS2-VASc score

In order to improve upon the prognostic utility of the CHADS2 score and to incorporate additional stroke risk factors, the CHA2DS2-VASc score has been proposed.[10]. These additional 'clinically relevant non-major' stroke risk factors include age 65-74, female gender, and vascular disease. In the CHA2DS2-VASc score, 'age 75 and above' also has extra weight, with 2 points.

The CHA2DS2-VASc score has been recommended in the 2010 European Society of Cardiology (ESC) guidelines [11] and the 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation[12], which promote a risk factor based approach to stroke prevention, and de-emphasizes the artificial stratification into low/moderate/high risk, given the poor predictive value of these 3 categories.

Click here to read more about the CHA2DS2-VASc score.

2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation (DO NOT EDIT)[12]

Prevention of Thromboembolism

Risk-Based Antithrombotic Therapy

See also: CHA2DS2-VASc Score
Class I
"1. Selection of antithrombotic therapy should be based on the risk of thromboembolism irrespective of whether the AF pattern is paroxysmal, persistent, or permanent. (Level of Evidence: B) "
"2. In patients with nonvalvular AF, the CHA2DS2-VASc score is recommended for assessment of stroke risk. (Level of Evidence: B) "
"3. For patients with nonvalvular AF with prior stroke, transient ischemic attack (TIA), or a CHA2DS2-VASc score of 2 or greater, oral anticoagulants are recommended. Options include: warfarin (INR 2.0 to 3.0) (Level of Evidence: A), dabigatran (Level of Evidence: B), rivaroxaban (Level of Evidence: B), or apixaban (Level of Evidence: B)."
"4. Re-evaluation of the need for and choice of antithrombotic therapy at periodic intervals is recommended to reassess stroke and bleeding risks. (Level of Evidence: C) "
"5. For patients with atrial flutter, antithrombotic therapy is recommended according to the same risk profile used for AF. (Level of Evidence: C) "
Class IIa
"1. For patients with nonvalvular AF and a CHA2DS2-VASc score of 0, it is reasonable to omit antithrombotic therapy. (Level of Evidence: B) "
Class IIb
"1. For patients with nonvalvular AF and a CHA2DS2-VASc score of 1, no antithrombotic therapy or treatment with an oral anticoagulant or aspirin may be considered. (Level of Evidence: C) "
"2. For patients with nonvalvular AF and moderate-to-severe CKD with CHA2DS2-VASc scores of 2 or greater, treatment with reduced doses of direct thrombin or factor Xa inhibitors may be considered (e.g., dabigatran, rivaroxaban, or apixaban), but safety and efficacy have not been established. (Level of Evidence: C) "
"3. Following coronary revascularization (percutaneous or surgical) in patients with AF and a CHA2DS2-VASc score of 2 or greater, it may be reasonable to use clopidogrel (75 mg once daily) concurrently with oral anticoagulants but without aspirin. (Level of Evidence: B) "

References

  1. 1.0 1.1 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.
  2. 2.0 2.1 2.2 2.3 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. PMID 11401607.
  3. Fuster V, Rydén LE, Cannom DS, Crijns HJ, Curtis AB, Ellenbogen KA et al. (2011). "2011 ACCF/AHA/HRS focused updates incorporated into the ACC/AHA/ESC 2006 Guidelines for the management of patients with atrial fibrillation: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines developed in partnership with the European Society of Cardiology and in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society.". J Am Coll Cardiol 57 (11): e101-98. doi:10.1016/j.jacc.2010.09.013. PMID 21392637.
  4. European Heart Rhythm Association. European Association for Cardio-Thoracic Surgery. Camm AJ, Kirchhof P, Lip GY, Schotten U et al. (2010). "Guidelines for the management of atrial fibrillation: the Task Force for the Management of Atrial Fibrillation of the European Society of Cardiology (ESC).". Europace 12 (10): 1360-420. doi:10.1093/europace/euq350. PMID 20876603.
  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. Welles CC, Whooley MA, Na B, et al. The CHADS(2) score predicts ischemic stroke in the absence of atrial fibrillation among subjects with coronary heart disease: Data from the Heart and Soul Study. Am Heart J. Sep 2011;162(3):555-61.
  7. 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.
  8. Hobbs FD, Roalfe AK, Lip GY, et al. Performance of stroke risk scores in older people with atrial fibrillation not taking warfarin: comparative cohort study from BAFTA trial. BMJ. Jun 23 2011;342:d3653.
  9. Steiner, Thorsten; Jonathan Rosand, Michael Diringer (2006). "Intracerebral hemorrhage associated with oral anticoagulant therapy: current practices and unresolved questions.". Stroke 37 (1): 256–62. PMID 16339459 doi:10.1161/01.STR.0000196989.09900.f8.
  10. 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.
  11. 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.
  12. 12.0 12.1 (2014) "2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society". Circulation. doi:10.1161/CIR.0000000000000041. ISSN 0009-7322.

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