The CHA2DS2-VASc score is used for long-term stroke risk stratification in patients with atrial fibrillation (AF). It is one of several stroke risk stratification schemas that can help determine the 1-year risk of a thromboembolic event in nonanticoagulated patients with nonvalvular AF. One recommended interpretation of the CHA2DS2-VASc score is that a score of 0 indicates low risk (anticoagulation may not be required); a score of 1 indicates low-moderate risk (antiplatelet or anticoagulation therapy should be considered); and a score of ≥2 indicates moderate-high risk (the patient is a candidate for anticoagulation).
Carefully evaluate all of the risks and benefits prior to initiating anticoagulation in patients with nonvalvular AF. Consider not starting anticoagulation in patients with nonvalvular AF and a CHA2DS2-VASc score of 0, as these patients had no thromboembolic events in the original study. When anticoagulation is considered, tools such as the ATRIA bleeding risk score can be used to determine the risk for warfarin-associated hemorrhage. Some guidelines have suggested that aspirin monotherapy is not supported by evidence.
Calvin Hwang, MD
The CHA2DS2-VASc score was developed following the identification of additional stroke risk factors in patients with AF using the Birmingham 2009 stroke risk stratification schema (Lip 2010). The valida-tion study included 1084 patients from the Euro Heart Survey who had nonvalvular AF diagnosed by electrocardiogram or Holter monitor. The study included patients aged ≥18 years from 182 hospitals across 35 countries in 2003 and 2004. Patients had known thromboembolic status at 1 year and were not on anticoagulation therapy. The endpoints were stroke or other thromboembolic event. The study found that as the CHA2DS2-VASc score increased, the rate of thromboembolic events within 1 year in nonanticoagulated patients with nonvalvular AF also increased. No thromboembolic events were recorded in cohort patients who were classified as low risk by the Birmingham 2009 schema (score = 0). There was 1 event (0.6% event rate at 1 year) among patients classified as intermediate risk (score = 1).
Thirty-one percent of the patients in the original study group were lost to follow-up at 1 year and thus were not included in the analysis; it is possible that some of these patients had thromboembolic events. There was no statistically significant difference found between the CHA2DS2-VASc and CHADS2 risk stratification scores in predicting thromboembolic events. None of the patients included in the study were anticoagulated, but patients at particularly high risk for a thromboembolic event may have been anticoagulated previously by their primary care physician, potentially skewing the thromboembolic rates. A subsequent study examining the performance of CHA2DS2-VASc in predicting thromboembolic events for anticoagulated patients identified coronary artery disease and smoking as potential additional risk factors for thromboembolic events in this subset of patients. However, that study also did not show a statistical difference in the various predictive risk stratification abilities of the scores.
Gregory Y. H. Lip, MD
Validation References
Additional References
The HAS-BLED score can help guide the decision on whether to start anticoagulation in patients with atrial fibrillation (AF). It can be used instead of, or in conjunction with, other bleeding risk scores such as ATRIA and HEMORR2HAGES to determine the risk of major bleeding in a patient with AF. Consider comparing the risk for major bleeding as calculated by the HAS-BLED score to the risk for thromboembolic events as calculated by the CHADS2 or CHA2DS2-VASc scores to determine if the benefit of anticoagulation outweighs the risk. Patient-specific risks and benefits of anticoagulation must be weighed carefully in all patients who are potential candidates for long-term anticoagulation therapy.
Calvin Hwang, MD
Clinical factors that contribute to stroke risk and support anticoagulation in patients with AF are frequently risk factors for bleeding as well. The HAS-BLED score was developed as a practical risk score to estimate the 1-year risk for major bleeding in patients with AF (Pisters 2010). The study included 5333 ambulatory and hospitalized patients with AF from both academic and nonacademic hospitals in 35 member countries of the European Society for Cardiology. Patients were followed up at 1 year to determine survival and major adverse cardiovascular events, such as major bleeding. Major bleeding was defined as any bleeding (excluding hemorrhagic stroke) that required hospitalization, caused a decrease in hemoglobin level of >2 g/dL, and/or required blood transfusion. The study authors performed a retrospective, univariate analysis to find potential bleeding risk factors when comparing the groups with and without major bleeding at 1-year follow-up. The HAS-BLED score was developed based on the results of that analysis and known significant risk factors for major bleeding. The study results showed that the annual bleeding rate increased as risk factors increased, with an overall major bleeding rate of 1.5%.
The original study for the HAS-BLED score provided risk percentages for given risk factors but did not categorize scores as low, medium, or high risk. The HAS-BLED score in its original form has not been externally validated. A modified version of the HAS-BLED score has been validated in a Japanese population; this study used different standards for hypertension and labile international normalized ratio and did not include alcohol consumption. In a study comparing the ATRIA, HEMORR2HAGES, and HAS-BLED scores, the HAS-BLED score showed superior performance compared to the 2 other scores.
Ron Pisters, MD
Original/Primary Reference
Validation References
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