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Using the CHA2DS2-VASc Score for Refining Stroke Risk Stratification in ‘Low-Risk’ Asian Patients With Atrial Fibrillation
Study Questions:
How well do the ATRIA and CHA2DS2-VASc scores compare for predicting stroke risk in low-risk atrial fibrillation (AF) patients?
Methods:
Using the universal National Health Insurance Research Database in Taiwan, a cohort of 186,570 patients with AF who were not prescribed antithrombotic therapy were followed between 1996 and 2011. The primary endpoint was the development of ischemic stroke, as identified on cerebral imaging. The CHA2DS2-VASc score includes points for congestive heart failure, hypertension, older age, prior stroke, vascular disease (prior myocardial infarction or peripheral artery disease), and female gender. The ATRIA score includes points for prior stroke, older age, diabetes, congestive heart failure, proteinuria, poor renal function, and female gender. Patients were deemed “low stroke risk” if their ATRIA score was 0-5.
Results:
During a mean follow up of 3.4 ± 3.7 years, 23,723 patients (12.7%) experienced an ischemic stroke. According to the ATRIA score, 39.3% of patients were deemed “low risk” for stroke. Among the 73,242 patients categorized as low-risk on the basis of an ATRIA score (0-5), the CHA2DS2-VASc score ranged from 0-7 and annual stroke rates ranged from 1.06-13.3% at 1 year of follow-up. The CHA2DS2-VASc score performed better than the ATRIA score when assessed by the c-statistic (0.698 vs. 0.627, p < 0.0001). The CHA2DS2-VASc score also improved the net reclassification index by 11.7% when compared to the ATRIA score (p < 0.0001).
Conclusions:
The authors concluded that there were varied rates of stroke and CHA2DS2-VASc scores in the cohort of patients categorized as “low risk” by the ATRIA score. In contrast, patients categorized as low risk by the CHA2DS2-VASc score had an annual stroke rate near 1%.
Perspective:
This study leverages the size and scope of the Taiwanese national health system database to describe the national history of AF in patients not receiving antithrombotic therapy. Of concern, this ‘untreated’ population represented more than half of all AF patients in their national database. This study also demonstrates that the ATRIA score, while rarely used clinically, is not sufficient for identifying truly ‘low risk’ patients for whom oral anticoagulation is likely to not be beneficial. At the present time, use of the CHA2DS2-VASc score is supported by the major society guidelines in both North America and Europe, and this study supports its use preferentially. It is important for clinicians to remember that aside from the very low risk patients (CHA2DS2-VASc of 0), the vast majority of AF patients should be treated with antithrombotic therapy, preferably oral anticoagulation.
Keywords: Myocardial Infarction, Stroke, Heart Failure, National Health Programs, Atrial Fibrillation, Proteinuria, Fibrinolytic Agents, Taiwan, Hypertension, Diabetes Mellitus
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