Abstract
Background and objectives
Previous studies have suggested that atrial fibrillation is a risk factor for pulmonary embolism. Oral anticoagulant therapy is the mainstay of treatment for atrial fibrillation and pulmonary embolism. We wanted to investigate if atrial fibrillation remained associated with the development of pulmonary embolism if oral anticoagulant treatment was accounted for.
Method
In this retrospective registry study a random sample of 20% of the adult Swedish population comprising approximately 1.5 million individuals were included during 2010–2017 in a cohort analysis. The endpoint was acute pulmonary embolism. In the cohort study, patients were analysed according to oral anticoagulant treatment and presence of atrial fibrillation at baseline.
Results
The group with atrial fibrillation was >25 years older than the group without and had almost three times higher incidence of pulmonary embolism (2.91 vs 1.09 /1000 year at risk, p<0.001). Individuals with atrial fibrillation on oral anticoagulant therapy had a lower risk of pulmonary embolism in multi-variable analysis (HR 0.59, CI 0.45–0.77). In the unadjusted analysis participants with atrial fibrillation without oral anticoagulant therapy showed an increased risk of pulmonary embolism (HR 3.33, CI 3.05–3.63). However, after multi-variable adjustment this association disappeared (HR 0.98, CI 0.89–1.07). In the entire atrial fibrillation cohort, no association was seen with the development of pulmonary embolism after multi-variable adjustment (HR 0.92, CI 0.84–1.01). The higher rate of pulmonary embolism among patients with atrial fibrillation can be fully explained by differences in age and co-morbidity.
Conclusion
Atrial fibrillation does not appear to be a clinically relevant risk factor for pulmonary embolism. Oral anticoagulant therapy protects against the development of pulmonary embolism in patients with atrial fibrillation.
Associations with pulmonary embolism
Funding Acknowledgement
Type of funding source: Other. Main funding source(s): The main author has received funding from Stockholm County Council (Clinical postdoctorial appointment)
Decision-Making in Clinical Practice: Oral Anticoagulant Therapy in Patients with Non-valvular Atrial Fibrillation and a Single Additional Stroke Risk Factor