Are low doses of non-vitamin K antagonists effective in Chinese patients with atrial fibrillation? A report from the Optimal Thromboprophylaxis in Elderly Chinese Patients with Atrial Fibrillation (ChiOTEAF) registry

Background Suboptimal low dosages of non-vitamin K antagonist oral anticoagulants (NOACs) are often inappropriately used due to a fear of bleeding, particularly among elderly patients. Such practice is common in Asia, and we aimed to evaluate the use of low-dose NOACs and their impact on clinical outcomes among Chinese patients with atrial fibrillation. Methods The Optimal Thromboprophylaxis in Elderly Chinese Patients with Atrial Fibrillation (ChiOTEAF) registry was a prospective, multicenter study conducted in China from October 2014 to December 2018. For this report, we included NOAC-treated patients with available data on NOAC dosage and one-year follow-up. Logistic regression analysis assessed the association (adjusted for age, sex, prior ischemic stroke, prior major bleeding, heart failure, coronary artery disease, hypertension, diabetes mellitus, chronic kidney disease, liver disease, current anemia) between the low doses and study outcomes among NOAC-treated patients, as well as comparisons with non-anticoagulated patients. Results The eligible cohort included 1310 NOAC-treated patients (mean age of 72.1 ± 10.9; 38.9% female), of whom 341 (26.0%) received a low “off-label” dose. The use of low-dose NOACs was independently associated with higher odds of the composite outcome (OR: 2.51; 95% CI: 1.11–5.71) and thromboembolism (OR: 4.73; 95% CI: 1.11–20.01). Compared with non-anticoagulated patients, lower rates of the composite outcome (7.3% vs. 11.3%; p = 0.025) and all-cause death (5.3% vs. 9.7%; p = 0.007) were seen in the low-dose group (ORs 0.50; 95% CI: 0.32–0.78, and 0.42; 95% CI: 0.26–0.70, respectively). Conclusions Low doses of NOACs should not be recommended as a part of standard therapy among Chinese patients with atrial fibrillation as their use was associated with a higher odds ratio of the composite outcome and thromboembolic events compared with standard dose NOAC regimens. Compared to non-treatment, the use of low-dose NOAC may result in a survival benefit (but not thromboembolic reduction) among high-risk patients.