Atrial fibrillation and risk of venous thromboembolism: a Swedish Nationwide Registry Study

Aims Atrial fibrillation (AF) is associated with arterial thromboembolism, mainly ischaemic stroke, while venous thromboembolism (VTE) in AF is less well studied. The aim of this study, therefore, was to examine the relationship between AF and VTE, including pulmonary embolism (PE) and deep venous thrombosis (DVT). Methods and results AF cases without previous VTE, ischaemic stroke or pulmonary arterial hypertension were identified from the Swedish Inpatient Registry between 1987 and 2013 and compared to two population controls per case without AF matched for age, sex, and county with respect to the incidence of VTE, PE, and DVT. In total, 463 244 AF cases were compared to 887 336 population controls. In both men and women, VTE rates were higher among AF patients the first 30 days after an AF diagnosis [40.2 vs. 5.7 in men and 55.7 vs. 6.6 in women per 1000 person-years at risk, respectively; hazard ratios 6.64 (95% confidence interval, 5.74-7.69) and 7.56 (6.47-8.83)]; and then decreasing, simultaneously with an increasing number of AF patients being treated with oral anticoagulation. VTE risk was similar to controls after 9 months in men but remained slightly elevated in women. Conclusion AF is strongly associated with an increased risk of VTE during the first months after diagnosis. Introduction of anticoagulant therapy soon after AF diagnosis might reduce the risk of VTE as well as of ischaemic stroke.