CHADS2 score

CHADS2 Score Microchapters
Overview
CHADS2 Score Original Study
CHADS2 Risk Score Calculator
Guideline

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sadaf Sharfaei M.D.[2]

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. 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.

CHADS2 Score Original Study

Description

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. 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.
• 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.

CHADS2 Risk Score Calculator

Calculation of the CHADS2 Score for Atrial Fibrillation Stroke Risk

CHADS2 Score for Atrial Fibrillation Stroke Risk
Variable	Score
Congestive Heart Failure	1
Hypertension: blood pressure consistently above 140/90 mmHg (or treated hypertension on medication)	1
Age ≥ 75 years	1
Diabetes Mellitus	1
Prior stroke or transient ischemic attack (TIA)	2
CHADS2 Score:
Interpretation:

Interpretation of the CHADS2 Score for Atrial Fibrillation Stroke Risk

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

• Score 0: Low risk (1.9% stroke risk, 95% CI 1.2-3.0); Consider Aspirin daily
• Score 1: Moderate risk (2.8% stroke risk, CI 2.0-3.8); Consider Aspirin or Warfarin depends on patient preference
• Score 2: Moderate risk (4% stroke risk, 95% CI 3.1-5.); Warfarin with an INR target of 2-3, unless contraindicated
• Score 3: Moderate risk (5.9% stroke risk, 95% CI 4.6-7.3); Warfarin with an INR target of 2-3, unless contraindicated
• Score 4: High risk (8.5% stroke risk, 95% CI 6.3-11.1); Warfarin with an INR target of 2-3, unless contraindicated
• Score 5: High risk (12.5% stroke risk, 95% CI 8.2-17.5); Warfarin with an INR target of 2-3, unless contraindicated
• Score 6: High risk (18.2% stroke risk, 95% CI 10.5-27.4); Warfarin with an INR target of 2-3, unless contraindicated

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

Prevention of Thromboembolism

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) "