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{{Seealso|Atrial fibrillation anticoagulation}}
{{Template:CHADS Score}}
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{{SK}} CHADS score


==Overview==
==Overview==
'''CHADS score''' or '''CHADS<sub>2</sub> score''' is a [[clinical prediction rule]] for estimating the risk of [[stroke]] in patients with [[rheumatic fever|non-rheumatic]] [[atrial fibrillation| atrial&nbsp;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,<ref name="pmid15477396 ">{{cite journal | title=Selecting patients with atrial fibrillation for anticoagulation: stroke risk stratification in patients taking aspirin | journal=Circulation | year=2004 | volume=110 | issue=16 | pages=2287&ndash;92 | author=Gage BF, van Walraven C, Pearce L, ''et al.'' | pmid=15477396 | doi=10.1161/01.CIR.0000145172.55640.93 | url=http://circ.ahajournals.org/cgi/content/full/110/16/2287}}</ref> since AF can cause stasis of blood in the upper [[Heart chamber|heart chambers]], leading to the formation of a [[mural thrombus]] that can dislodge into the blood flow, reach the brain, cut off blood supply to the brain, and cause a stroke. A high CHADS<sub>2</sub> score corresponds to a greater risk of stroke, while a low CHADS<sub>2</sub> score corresponds to a lower risk of stroke. The CHADS<sub>2</sub> score was validated by a study of nonrheumatic atrial fibrillation patients aged 65 to 95 who were not prescribed the anticoagulant [[warfarin]].<ref name=Gage2001>{{cite journal |author=Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ |title=Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation |journal=JAMA |volume=285 |issue=22 |pages=2864–70 |year=2001 |url=http://jama.ama-assn.org/cgi/content/full/285/22/2864 |pmid=11401607 |doi=}}</ref>
CHADS<sub>2</sub> score is a [[clinical prediction rule]] for the estimation of the risk of [[stroke]] among patients with [[rheumatic fever|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]].  CHADS<sub>2</sub> score is used to assess the risk of stroke and determine whether or not antithrombotic therapy is required with either [[anticoagulant]]s therapy or antiplatelets for the prevention of thromboembolism.<ref name="pmid15477396">{{cite journal | title=Selecting patients with atrial fibrillation for anticoagulation: stroke risk stratification in patients taking aspirin | journal=Circulation | year=2004 | volume=110 | issue=16 | pages=2287&ndash;92 | author=Gage BF, van Walraven C, Pearce L, ''et al.'' | pmid=15477396 | doi=10.1161/01.CIR.0000145172.55640.93 | url=http://circ.ahajournals.org/cgi/content/full/110/16/2287}}</ref>  A high CHADS<sub>2</sub> score corresponds to a greater risk of stroke, while a low CHADS<sub>2</sub> score corresponds to a lower risk of stroke. The CHADS<sub>2</sub> score was validated by a study on non-rheumatic AF patients aged 65 to 95 who were not prescribed the anticoagulant [[warfarin]].<ref name="Gage2001">{{cite journal |author=Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ |title=Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation |journal=JAMA |volume=285 |issue=22 |pages=2864–70 |year=2001 |url=http://jama.ama-assn.org/cgi/content/full/285/22/2864 |pmid=11401607 |doi=}}</ref>


==Method==
==CHADS2 Score Original Study==
The CHADS<sub>2</sub> scoring table is shown above:<ref> {{cite web|url=http://www.cardiology.org/tools/risk_of_stroke_AF.html |title=Risk of Stroke with AF |accessdate=2007-09-14 |publisher=VA Palo Alto Medical Center and at Stanford University: the Sportsmedicine Program and the Cardiomyopathy Clinic }}</ref><br />


Adding together the points that correspond to the conditions that a patient has will result in the CHADS<sub>2</sub>
=== Description ===
score. This score is used in the next section to estimate stroke risk. <br>
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).


{| class="wikitable" style = "float: left; margin-left:15px; text-align:center"
===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.
!Condition
* 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.
!Points
* 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 CHADS<sub>2</sub> score has various limitations, which have been debated.<ref>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.</ref>  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.<ref>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.</ref>
* 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 CHADS<sub>2</sub> 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.<ref name="Steiner2006">{{cite journal|title=Intracerebral hemorrhage associated with oral anticoagulant therapy: current practices and unresolved questions.|journal=Stroke|year=2006|first=Thorsten|last=Steiner|coauthors=Jonathan Rosand, Michael Diringer|volume=37|issue=1|pages=256–62|id=PMID 16339459 {{doi|10.1161/01.STR.0000196989.09900.f8}}|url=http://stroke.ahajournals.org/cgi/reprint/37/1/256|format=|accessdate= }}</ref>
 
==CHADS2 Risk Score Calculator==
 
=== Calculation of the CHADS2 Score for Atrial Fibrillation Stroke Risk ===
{{#Widget:CHADS2score}}
 
===Interpretation of the CHADS2 Score for Atrial Fibrillation Stroke Risk===
Shown below is the probability of the annual stroke risk by the corresponding CHADS<sub>2</sub> score value.<ref name="Gage2001" />
* 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<ref name="JanuaryWann2014">{{cite journal|last1=January|first1=C. T.|last2=Wann|first2=L. S.|last3=Alpert|first3=J. S.|last4=Calkins|first4=H.|last5=Cleveland|first5=J. C.|last6=Cigarroa|first6=J. E.|last7=Conti|first7=J. B.|last8=Ellinor|first8=P. T.|last9=Ezekowitz|first9=M. D.|last10=Field|first10=M. E.|last11=Murray|first11=K. T.|last12=Sacco|first12=R. L.|last13=Stevenson|first13=W. G.|last14=Tchou|first14=P. J.|last15=Tracy|first15=C. M.|last16=Yancy|first16=C. W.|title=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|journal=Circulation|year=2014|issn=0009-7322|doi=10.1161/CIR.0000000000000041}}</ref>===
 
{| class="wikitable" style="width: 80%;"
|-
|-
| &nbsp;'''C'''&nbsp;
| colspan="1" style="text-align:center; background:LightGreen" |[[ACC AHA guidelines classification scheme#Classification of Recommendations|Class I]]
| &nbsp;[[Congestive heart failure]]
| <center>1</center>
|-
|-
| &nbsp;'''H'''  
| bgcolor="LightGreen" |<nowiki>"</nowiki>'''1.''' Selection of [[antithrombotic therapy]] should be based on the risk of [[thromboembolism]] irrespective of whether the [[AF]] pattern is paroxysmal, persistent, or permanent. ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: B]])'' <nowiki>"</nowiki>
| &nbsp;[[Hypertension]]: blood pressure consistently above 140/90 mmHg (or treated hypertension on medication)
| <center>1</center>
|-
|-
| &nbsp;'''A'''  
| bgcolor="LightGreen" |<nowiki>"</nowiki>'''2.''' In patients with nonvalvular [[AF]], the [[CHA2DS2-VASc score]] is recommended for assessment of stroke risk. ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: B]])'' <nowiki>"</nowiki>
| &nbsp;Age >/=75 years
| <center>1</center>
|-
|-
| &nbsp;'''D'''  
| bgcolor="LightGreen" |<nowiki>"</nowiki>'''3.''' For patients with nonvalvular [[AF]] with prior [[stroke]], [[TIA|transient ischemic attack (TIA)]], or a [[CHA2DS2-VASc score]] of 2 or greater, oral [[anticoagulant]]s are recommended. Options include: [[warfarin]] ([[INR]] 2.0 to 3.0) ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: A]])'', [[dabigatran]] ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: B]])'', [[rivaroxaban]] ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: B]])'', or [[apixaban]] ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: B]])''.<nowiki>"</nowiki>
| &nbsp;[[Diabetes Mellitus]]
| <center>1</center>
|-
|-
| &nbsp;'''S<sub>2</sub>'''
| bgcolor="LightGreen" |<nowiki>"</nowiki>'''4.''' Re-evaluation of the need for and choice of [[antithrombotic therapy]] at periodic intervals is recommended to reassess [[stroke]] and [[bleeding]] risks. ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: C]])'' <nowiki>"</nowiki>
| &nbsp;Prior [[Stroke]] or [[Transient ischemic attack | TIA]]
|-
| <center>2</center>
| bgcolor="LightGreen" |<nowiki>"</nowiki>'''5.''' For patients with [[atrial flutter]], [[antithrombotic therapy]] is recommended according to the same risk profile used for [[AF]]. ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: C]])'' <nowiki>"</nowiki>
|}
|}
{{Clr}}


==Risk of stroke==
{| class="wikitable" style="width: 80%;"
{| class="wikitable" style = "float: right; margin-left:15px; text-align:center"
|+Annual Stroke Risk<ref name=Gage2001 />
|-
! CHADS<sub>2</sub> Score
! &nbsp;&nbsp;Stroke Risk %
! &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;95% [[Confidence interval | CI]]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
|-
| <center>'''0'''</center>
| <center>1.9</center>
| <center>&nbsp;1.2–3.0</center>
|-
| <center>'''1'''</center>
| <center>2.8</center>
| <center>&nbsp;2.0–3.8</center>
|-
| <center>'''2'''</center>
| <center>4.0</center>
| <center>&nbsp;3.1–5.1</center>
|-
|-
| <center>'''3'''</center>
| colspan="1" style="text-align:center; background:LemonChiffon" |[[ACC AHA guidelines classification scheme#Classification of Recommendations|Class IIa]]
| <center>5.9</center>
| <center>&nbsp;4.6–7.3</center>
|-
|-
| <center>'''4'''</center>
| bgcolor="LemonChiffon" |<nowiki>"</nowiki>'''1.''' For patients with nonvalvular [[AF]] and a [[CHA2DS2-VASc score]] of 0, it is reasonable to omit [[antithrombotic therapy]]. ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: B]])'' <nowiki>"</nowiki>
| <center>8.5</center>
| <center>&nbsp;6.3–11.1</center>
|-
| <center>'''5'''</center>
| <center>12.5</center>
| <center>&nbsp;8.2–17.5</center>
|-
| <center>'''6'''</center>
| <center>18.2</center>
| <center>10.5–27.4</center>
|}
|}
According to the findings of the validation study, the risk of stroke as a percentage per year is shown in the table titled Annual Stroke Risk:


While the CHADS<sub>2</sub> score provides prognostic information regarding the natural history of non-valvular atrial fibrillation (NVAF) in the absence of warfarin therapy, it should be noted that warfarin therapy also has an associated stroke risk<ref name='Steiner2006'> {{cite journal|title=Intracerebral hemorrhage associated with oral anticoagulant therapy: current practices and unresolved questions.|journal=Stroke|year=2006|first=Thorsten|last=Steiner|coauthors=Jonathan Rosand, Michael Diringer|volume=37|issue=1|pages=256–62|id=PMID 16339459 {{doi|10.1161/01.STR.0000196989.09900.f8}}|url=http://stroke.ahajournals.org/cgi/reprint/37/1/256|format=|accessdate= }}</ref> (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.
{| class="wikitable" style="width: 80%;"
 
The CHADS<sub>2</sub> score has various limitations, which have been debated <ref>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.</ref>.  Notably, many stroke risk factors have not been included, and whilst simple, the score has only modest predictive value for thromboembolism.
 
In order to improve upon the prognostic utility of the CHADS<sub>2</sub> score and to incorporate additional stroke risk factors, the [[CHA2DS2-VASc score]] has been proposed <ref>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.</ref>.  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 used in the new [http://www.escardio.org/guidelines-surveys/esc-guidelines/Pages/atrial-fibrillation.aspx European Society of Cardiology guidelines for the management of atrial fibrillation] <ref>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.</ref>.
 
The European Society of Cardiology (ESC) guidelines recommend that if the patient has a CHADS<sub>2</sub> score of 2 and above, oral anticoagulation (OAC) therapy is recommended. OAC options include warfarin with an [[INR]] target of 2-3 or [[dabigatran]]. 
 
If the CHADS<sub>2</sub> score is 0-1, other stroke risk modifiers should 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), then antithrombotic therapy with either OAC or aspirin (OAC preferred) is recommended.
 
If patients have a [[CHA2DS2-VASc score]] of 0, then such patients are ‘truly low risk’<ref>Van Staa TP, Setakis E, Di Tanna GL, Lane DA, Lip GY. A comparison of risk stratification schema for stroke in 79884 atrial fibrillation patients in general practice. J Thromb Haemost. 2010 Oct 1. doi: 10.1111/j.1538-7836.2010.04085.x. [Epub ahead of print] PubMed PMID: 21029359.</ref>. The ESC guidelines recommend either aspirin or no antithrombotic therapy, but 'no antithrombotic therapy' is preferred<ref>Lip GY, Halperin JL. Improving stroke risk stratification in atrial fibrillation. Am J Med. 2010 Jun;123(6):484-8. </ref>.
 
==Anticoagulation based on the CHADS<sub>2</sub> score ==
The following treatment strategies are recommended in the table below entitled Anticoagulation based on the CHADS2 score:<ref name="pmid15477396 " /><ref name=Gage2001 />
 
{| class="wikitable" style = "float: right; margin-left:15px; text-align:center"
|-
|-
! Score
| colspan="1" style="text-align:center; background:LemonChiffon" |[[ACC AHA guidelines classification scheme#Classification of Recommendations|Class IIb]]
! Risk
! Anticoagulation Therapy
! Considerations
|-
|-
| '''0'''
| bgcolor="LemonChiffon" |<nowiki>"</nowiki>'''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. ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: C]])'' <nowiki>"</nowiki>
| Low
| [[Aspirin]]
| Aspirin daily
|-
|-
| '''1'''
| bgcolor="LemonChiffon" |<nowiki>"</nowiki>'''2.''' For patients with nonvalvular [[AF]] and moderate-to-severe [[CKD]] with [[CHA2DS2-VASc score]]s of 2 or greater, treatment with reduced doses of [[DTI|direct thrombin]] or [[Direct Xa inhibitor|factor Xa inhibitors]] may be considered (e.g., [[dabigatran]], [[rivaroxaban]], or [[apixaban]]), but safety and efficacy have not been established. ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: C]])'' <nowiki>"</nowiki>
| Moderate
| Aspirin or Warfarin
| Aspirin daily or [[International normalized ratio|INR]] to 2.0-3.0, depending on factors such as patient preference
|-
|-
| '''2 or greater'''
| bgcolor="LemonChiffon" |<nowiki>"</nowiki>'''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 [[anticoagulant]]s but without [[aspirin]]. ''([[ACC AHA guidelines classification scheme#Level of Evidence|Level of Evidence: B]])'' <nowiki>"</nowiki>
| Moderate or High
| [[Warfarin]]
| [[International normalized ratio|INR]] to 2.0-3.0, unless contraindicated (e.g. clinically significant GI bleeding, inability to obtain regular INR screening)
|}
|}
For detailed recommendations on how the treatment recommendations based on the CHADS<sub>2</sub> score are modified by considering additional 'stroke risk modifier' risk factors using the [[CHA2DS2-VASc score]], see [http://www.escardio.org/guidelines-surveys/esc-guidelines/Pages/atrial-fibrillation.aspx ESC guideline] recommendations.
==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 <ref>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.</ref> 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 were recently hospitalized rather than healthier individuals, it is thought that CHADS2 should be generalizable to frail and elderly individuals
[[Validation_of_Clinical_Classification_Schemes_for_Predicting_Stroke.pptx‎]]
==Limitations==
* 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 <ref>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.</ref>.
* 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 that were older and sicker. The CHADS2 study was based on the SPAF and AFI schemes, therefore the study may have performed better if it were 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 for aspirin effectiveness in preventing stroke was not statistically significant in this study (however there is clinical significance when the study is combined with other research, and the results suggest that aspirin therapy should be prescribed for elderly patients with AF).
<br>
==References==
==References==
{{reflist|2}}
{{reflist|2}}


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Latest revision as of 20:52, 29 July 2020

Template:Seealso

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.[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]

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.[3] 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.[4]
  • 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.[5]

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.[2]

  • 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[6]

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. ↑ 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&ndash, 92. doi:10.1161/01.CIR.0000145172.55640.93. PMID 15477396.
  2. ↑ 2.0 2.1 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. ↑ 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.
  4. ↑ 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.
  5. ↑ Steiner, Thorsten (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. Unknown parameter |coauthors= ignored (help)
  6. ↑ January, C. T.; Wann, L. S.; Alpert, J. S.; Calkins, H.; Cleveland, J. C.; Cigarroa, J. E.; Conti, J. B.; Ellinor, P. T.; Ezekowitz, M. D.; Field, M. E.; Murray, K. T.; Sacco, R. L.; Stevenson, W. G.; Tchou, P. J.; Tracy, C. M.; Yancy, C. W. (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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