P658CHA2DS2-VASc score calibration in anticoagulated vs non-anticoagulated patients in a healthcare area

Abstract

Introduction Atrial fibrillation (AF) is a highly prevalent heart disease, affecting a significant proportion of patients over 65 years old. The CHA2DS2-VASc score predicts 1 year risk of a thromboembolic (TE) event and is well validated against several populations. However, calibration may vary if there is subgroup heterogeneity. Purpose To compare the CHA2DS2-VASc score calibration, in patients with or without anticoagulation (AC) in a real population of AF patients in our healthcare area. Methods Patients with an episode with atrial fibrillation/flutter were selected from a general population in a healthcare area (383,000 subjects), with 21/12/2013 as a cut-off date. Patients with valve disease, anticoagulation or antiplatelet therapy were identified. The CHA2DS2-VASc score was calculated as stipulated in the European Society of Cardiology guidelines. A CHA2DS2-VASc score of 0 is considered to be low risk for TE events (0% at 1 year), score of 1 intermediate risk (0.6% rate at 1 year), and greater than 1 high risk (3% rate at 1 year). Quantitative variables are presented as mean and standard deviation (SD). Categorical variables were presented as frequencies and percentages. A logistic regression was fitted to predict 1-year risk TE outcomes with CHA2DS2-VASc as the only covariate. Model calibration was assessed using the predicted versus actual probabilities of TE events. All analyses were performed using R v.3.4 (R Core Team, Vienna, Austria) with the packages rms and ggplot2. Results CHA2DS2-VASc was calculated in 7990 patients with AF. A total of 1824 patients were excluded either due to valvular disease (846) or due to previous antiplatelet treatment (1047). From them, 143 patients were excluded for an incomplete follow-up time (<1 year). As of December 31, 2015, 67 stroke cases had been notified from 6023 patients (1.1%) (Table 1). Mortality rate was 181 (3%) at 1 year. Patients presented overall low risks of stroke with a poor score calibration. Higher scores presented risks that were lower than predicted by CHA2DS2-VASc. Event rate at 1 year was similar regardless of the AC regime at the initial date, and also similar to a previous cohort of anticoagulated patients (Lip et al.). This similarity may indicate confounding by later AC therapy initiation, before the final assessment date. Table 1. Comparison of thromboembolic event rates in several studies % (No-AC) % (AC) % Lip 2010 % Poli 2011 % Friberg 2012 % Okumura 2014 0.01 0.01 0.02 4.5 4.5 1 AC: anticoagulation. CHA2DS2VASc score calibration Conclusion Higher CHA2DS2-VASc scores are not associated to higher risks of stroke in our healthcare area, in patients with non-valvular AF and without antiplatelet therapy.