Reassessment of Risk for Stroke During Follow-up of Patients With Atrial Fibrillation

Background: International guidelines suggest that oral anticoagulants (OACs) can be omitted for patients with atrial fibrillation (AF) without a CHA2DS2-VASc score greater than 0 (men) or 1 (women) (1, 2). However, stroke risk is not static among patients with AF, and about 90% develop at least 1 new risk factor before presentation with ischemic stroke (3). Therefore, patients with AF who have a CHA2DS2-VASc score of 0 (men) or 1 (women) at baseline and acquire more comorbidities over time would no longer be low-risk. Objective: To investigate incidence of an increase in CHA2DS2-VASc score to at least 1 (men) or 2 (women) among patients with newly diagnosed AF and a baseline score of 0 (men) or 1 (women). Methods and Findings: From 1 January 1997 to 31 December 2010, a total of 14606 patients with newly diagnosed AF and a CHA2DS2-VASc score of 0 (n= 8745 men) or 1 (n= 5861 women) who did not receive antiplatelets or OACs were identified in the Taiwan National Health Insurance Research Database (NHIRD). New onset of AF was assumed if no diagnosis was found in the database from 1 January 1996 to the date of diagnosis of incident AF (index date). The absence of CHA2DS2-VASc comorbidities in patients with incident AF was ascertained from the index date back to 1 January 1996. Acquisition of incident comorbidities and, therefore, an increase in CHA2DS2-VASc score was based on whether International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM), codes for the comorbidities were registered in NHIRD by physicians who cared for the patients. The study end point was an increase in CHA2DS2-VASc score to at least 1 (men) or 2 (women). Patients were censored at occurrence of ischemic stroke or death, at the start of antiplatelet or OAC use, 7 years after incident AF, or on 31 December 2011, whichever came first. The diagnostic accuracy of ICD-9-CM codes in NHIRD for important comorbidities, such as hypertension, diabetes, heart failure, myocardial infarction, and ischemic stroke, has been validated (4). Cumulative incidence curves for increases in CHA2DS2-VASc scores were plotted using the KaplanMeier method. All statistical analyses were performed using R, version 3.2. 5 (R Foundation for Statistical Computing). The mean age of the study population was 47.8 years (SD, 11.5). During a mean follow-up of 3.24 years (47275 total person-years), 5301 (36.3%) patients with AF acquired at least 1 new risk factor. In men, the cumulative incidence of an increase in CHA2DS2-VASc score to 1 or higher was 16.1% (95% CI, 15.2% to 16.9%) at 1 year, 24.5% (CI, 23.5% to 25.5%) at 2 years, and 49.1% (CI, 47.8% to 50.3%) at 7 years (Figure). In women, the cumulative incidence of an increase in CHA2DS2-VASc score to 2 or higher was 16.2% (CI, 15.1% to 17.1%) at 1 year, 24.9% (CI, 23.7% to 26.1%) at 2 years, and 49.9% (CI, 48.4% to 51.4%) at 7 years (Figure). The numbers of ischemic strokes and deaths in each interval are also shown in the Figure. Figure. Cumulative incidence curves for increases in CHA2DS2-VASc score to 1 (men) or 2 (women). During follow-up, 5301 (36.3%) patients with atrial fibrillation acquired 1 new risk factor, and 16.1% of men and 16.2% of women had an increase in their score 1 y after incident atrial fibrillation. Discussion: Guidelines state that individual risk varies over time, so the need for anticoagulation must be re-evaluated periodically in all patients with AF (5). This is particularly important for patients with AF who have a CHA2DS2-VASc score of 0 (men) or 1 (women) at baseline. These patients are classified as low-risk and thus do not receive OACs. However, their scores may increase after AF is diagnosed, and use of OACs should be initiated to prevent stroke when patients are no longer at low risk. Despite recognition of the importance of regular reevaluation of stroke risk in patients who initially have low risk to avoid delayed initiation of use of OACs, a reasonable interval for risk assessment has not been previously studied. In our analysis, about 16.1% of men and 16.2% of women who were initially at low risk had a CHA2DS2-VASc score of at least 1 (men) or 2 (women) 1 year after incident AF. Therefore, we propose that CHA2DS2-VASc scores should be reassessed at least annually in patients with AF so that OACs can be prescribed in a timely manner for stroke prevention.