A diagnosis of atrial fibrillation is not a predictor for pulmonary embolism

BACKGROUND AND OBJECTIVES: Atrial fibrillation causes stroke by embolization of blood clots from the left atrium. This suggests that it also can cause pulmonary embolism through embolization of thrombi from the right atrium. Our objective was to investigate if atrial fibrillation is an independent risk factor for pulmonary embolism. METHOD: This is a retrospective registry study of a random sample of 1.5 million Swedish residents alive on January 1, 2010 (n = 1,442,028) who were followed until the end of 2017. Information about comorbidity, medication and outcomes was obtained from the Swedish national health registers. The endpoint was a first-time event of pulmonary embolism. RESULTS: The group with atrial fibrillation was >25 years older (mean) than the group without and had almost three times higher incidence of pulmonary embolism (2.91 and 1.09 per 1000 year at risk, p < 0.001). After adjustment for age and other co-factors, atrial fibrillation without oral anticoagulant protection was not associated with increased risk for pulmonary embolism (HR 1.03, CI 0.94-1.13). Adjustment for the competing risk of dying showed similar results (sHR 0.99, CI 0.70-1.40). The higher rate of pulmonary embolism among patients with atrial fibrillation can be fully explained by differences in age and comorbidity. CONCLUSION: A diagnosis of atrial fibrillation is not a predictor for pulmonary embolism.