The CHADS
2 score and its updated version, the CHA
2DS
2-VASc score, are
clinical prediction rule A clinical prediction rule or clinical probability assessment specifies how to use medical signs, symptoms, and other findings to estimate the probability of a specific disease or clinical outcome.
Physicians have difficulty in estimated risks of ...
s for estimating the risk of
stroke
A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...
in people with
non-rheumatic atrial fibrillation (AF), a common and serious
heart arrhythmia
Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adult ...
associated with thromboembolic stroke. Such a score is used to determine whether or not treatment is required with
anticoagulation
Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...
therapy or antiplatelet therapy,
since AF can cause stasis of blood in the upper
heart chamber
The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...
s, 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 score corresponds to a greater risk of stroke, while a low score corresponds to a lower risk of stroke. The CHADS
2 score is simple and has been validated by many studies.
In clinical use, the CHADS
2 score (pronounced "chads two") has been superseded by the CHA
2DS
2-VASc score ("chads vasc"), which gives a better stratification of low-risk patients.
Use
The CHA
2DS
2-VASc score is a widely used
medical tool used to guide physicians on
blood thinning treatment to prevent
stroke
A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...
in people with non-valvular
atrial fibrillation (AF).
CHADS2
The CHADS
2 score does not include some common stroke risk factors, and its various pros/cons have been carefully discussed. Adding together the points that correspond to the conditions that are present results in the CHADS
2 score, that is used to estimate stroke risk.
CHA2DS2-VASc
To complement the CHADS
2 score, by the inclusion of additional 'stroke risk modifier' risk factors, the CHA
2DS
2-VASc-score has been proposed.
In clinical use, the CHADS
2 score has been superseded by the CHA
2DS
2-VASc score, which gives a better stratification of low-risk patients. The CHADS
2 score has been outperformed by the CHA
2DS
2-VASc in multiple patient groups including patients with AF who are receiving outpatient elective electrical cardioversion.
Thus, the CHA
2DS
2-VASc score is a refinement of CHADS
2 score and extends the latter by including additional common stroke risk factors, that is, age 65–74, female gender and vascular disease. In the CHA
2DS
2-VASc score, 'age 75 and above' also has extra weight, with 2 points.
The maximum CHADS
2 score is 6, whilst the maximum CHA
2DS
2-VASc score is 9 (not 10, as might be expected from simply adding up the columns; the maximum score for age is 2 points).
Major guidelines have used the above fixed annual stroke risk as a guideline of starting anticoagulant treatment; where the ischemic stroke risk of more than 1% to 2% should be an indication to start an anticoagulant therapy. However, actual risk of getting stroke varies according to sampling method and geographical regions, as well as use of appropriate study analysis methodology. A meta-analysis of various studies in 2015 shown that annual stroke risk is less than 1% in 13 of the 17 studies for CHA
2DS
2-VASc score of 1, 6 out of 15 studies reported risk of 1 to 2% and 5 out of 15 studies reported risk of more than 2% for CHA
2DS
2-VASc score of 2. Nevertheless, stroke rates vary by study setting (hospital vs community), population (trial vs general), ethnicity, etc. Some studies included in the metaanalysis include females with score 1 by virtue of gender (who are low risk), into the aggregate rates; others included do not account for followup anticoagulation use (thus lowering rates) and were analysed by excluding all patients ever started on anticoagulants ('conditioning on the future' error).
The CHA
2DS
2-VASc Score has shown increasing popularity over time while the CHADS
2 has shown decreasing popularity,
which could "partly be related to introduction of guidelines recommending the use of the CHA
2DS
2-VASc score for stroke risk stratification".
The predictive abilities of risk scores for ischemic stroke in patients with kidney function impairment is questionable: a large head-to-head external validation study demonstrated poor discrimination and calibration in patients with reduced kidney function.
Treatment recommendations
The CHA
2DS
2-VASc score has been used in the 2012 and subsequent
European Society of Cardiology
The European Society of Cardiology (ESC) is an independent non-profit, non-governmental professional association that works to advance the prevention, diagnosis and management of diseases of the heart and blood vessels, and improve scientific u ...
guidelines for the management of
atrial fibrillation.
The 2014
American College of Cardiology
The American College of Cardiology (ACC), based in Washington, D.C., is a nonprofit medical association established in 1949. It bestows credentials upon cardiovascular specialists who meet its qualifications. Education is a core component of the ...
/American Heart Association Task Force on Practice Guidelines and the
Heart Rhythm Society guidelines also recommend use of the CHA
2DS
2-VASc score.
The European Society of Cardiology (ESC),
and
National Institute for Health and Care Excellence (NICE) guidelines recommend that if the patient has a CHA
2DS
2-VASc score of 2 and above, oral anticoagulation therapy (OAC) with a vitamin K antagonist (VKA, e.g. warfarin with target
INR of 2-3) or one of the
direct oral anticoagulant drugs (DOACs, e.g. dabigatran, rivaroxaban, edoxaban, or apixaban) is recommended.
If the patient is 'low risk' using the CHA
2DS
2-VASc score (that is, 0 in males or 1 in females), no anticoagulant therapy is recommended.
In males with 1 stroke risk factor (that is, a CHA
2DS
2-VASc score=1), antithrombotic therapy with OAC may be considered, and people's values and preferences should be considered. Even a single stroke risk factor confers excess risk of stroke and mortality, with a positive net clinical benefit for stroke prevention with oral anticoagulation, when compared to no treatment or aspirin. As mentioned above, thromboembolic event rates differ according to various guideline treatment thresholds and methodological approaches.
Anticoagulation
Treatment recommendations based on the CHA
2DS
2-VASc score are shown in the following table:
Based on the ESC guidelines on AF, oral anticoagulation is recommended or preferred for people with one or more stroke risk factors (i.e. a CHA
2DS
2-VASc score of ≥1 in males, or ≥2 in females).
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 the 'safer' DOAC drugs, where the threshold for offering stroke prevention (i.e. oral anticoagulation) is a stroke rate of approximately 1%/year.
Those patients recommended for stroke prevention treatment via oral anticoagulation, choice of drug (i.e. between a vitamin K antagonist and direct oral anticoagulant (DOAC)) can be evaluated using the
SAMe-TT2R2 score to help decision-making on the most appropriate oral anticoagulant.
Bleeding risk
Stroke risk assessment should always include an assessment of bleeding risk. This can be done using validated bleeding risk scores, such as the HEMORR
2HAGES or
HAS-BLED
HAS-BLED is a scoring system developed to assess 1-year risk of major bleeding in people taking anticoagulants for atrial fibrillation (AF). It was developed in 2010 with data from 3,978 people in the Euro Heart Survey.
Major bleeding is defined ...
scores. The HAS-BLED score is recommended in guidelines, to identify the high risk patient for regular review and followup and to address the reversible risk factors for bleeding (e.g. uncontrolled hypertension, labile INRS, excess alcohol use or concomitant aspirin/NSAID use).
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 criterion scores zero. A high HAS-BLED score is not a reason to withhold anticoagulation. Also, when compared to HAS-BLED, other bleeding risk scores that did not consider 'labile INR' would significantly underperform in predicting bleeding on warfarin, and would often inappropriately categorise many patients who sustained bleeds as 'low risk'.
History
The CHA
2DS
2-VASc score expanded from the CHADS2 score, first published in 2001.
References
External links
Dosing informationgiven CHADS
2 Score
Online calculator of the CHA2DS2-VASc score
{{DEFAULTSORT:Chads Score
Diagnostic cardiology
Stroke
Medical scoring system
Medical mnemonics