Dynamic change in anticoagulation pattern at age 65 years in patients with atrial fibrillation and prior low thromboembolic risk

Abstract Background Atrial Fibrillation (AF) is common in elderly patients. Age ≥65 years is an independent thromboembolic risk factor in patients with AF and is an indication for the initiation of anticoagulant therapy based on CHA2DS2VASc scale. Despite this, it may be controversial to justify an arbitrary cut-off for a continuous variable to determine that risk. Objectives The primary endpoint was to assess whether the initiation of anticoagulation therapy in patients who were 65 years old prevents ischemic stroke events in low thromboembolic risk individuals at baseline (CHA2DS2VASc 0 points in male and 1 in women). Another aim was to evaluate whether there were differences in major bleeding events in this population. Methods We used data from the CardioCHUVI-AF registry that included 16202 patients with a diagnosis of AF from the Vigo Health Area between January 2014 and January 2018 Of these, 861 individuals (5.3%) had low embolic risk at baseline. Eight patients with Hypertrophic Cardiomyopathy, 26 with mechanical prostheses and 3 with mitral stenosis were excluded. Of the remaining 824 patients, 389 (2.4%) ceased to belong to this low embolic risk group due to age (≥65 years) during the follow-up period. Univariate analysis was performed with age ≥65 years to compare the incidence of ischemic stroke and major bleeding events in anticoagulated patients with those in non-anticoagulated patients. Results A total of 389 patients with a diagnosis of AF and initial low embolic risk were followed for 8.1±1.5 years (median 8.9, IQR 7.8-9.0 years). The mean age at the start of follow-up was 60.9±2.7 years. Before the age of 65, 187 patients (48.1%) were anticoagulated. A total of 261 patients were under anticoagulant treatment after turn to 65 years (67.1%, an increase of 19.0% in the rate of anticoagulation). Therefore, 32.9% of the individuals were not anticoagulated despite the fact that they had an indication at that time. In the Kaplan-Meier curves of our study population before reaching 65 years of age, no significant differences were observed in the rate of ischemic stroke events between anticoagulated and non-anticoagulated patients [HR, 1.22; 95%CI 0.41-3.64; p=0.718] or in the rate of major bleeding [HR 1.03, 95%CI 0.36-2.95; p=0.949]. However, in the same population that had already reached 65 years of age at the end of follow-up, statistically significant differences were observed in favor of anticoagulated patients in the incidence of ischemic stroke [HR 0.19, 95%CI 0.05-0.77; p=0.020] without an increase in the rate of hemorrhagic events [HR 0.85, 95%CI 0.32-2.27; p=0.745]. Conclusions Our registry highlights the dynamic nature of the CHA2DS2VASc scale based on age. Thus, patients with a CHA2DS2VASc score of 0 points (1 if they are women) who are close to 65 years should be evaluated periodically, starting anticoagulation therapy at that age.