Introduction: The prevalence of pulmonary embolism (PE) among patients with syncope is understudied. Based on a recent study with an exceptionally high PE prevalence, some advocate investigating all syncope patients for PE, including those with another clear cause for their syncope. We sought to evaluate the PE prevalence among emergency department (ED) patients with syncope. Methods: We combined data from two large prospective studies enrolling adults with syncope from 17 EDs in Canada and the United States. Each study collected the results of investigations related to PE (i.e. D-dimer or ventilation-perfusion (VQ) scan, or computed tomography pulmonary angiogram (CTPA)), and 30-day adjudicated outcomes including diagnosis of PE, arrhythmia, myocardial infarction, serious hemorrhage and/or death. Results: Of the 9,091 patients (median age 66 years, 51.9% females, 39.1% hospitalized) with 30-day follow-up, 546 (6.0%) were investigated for PE: 278 (3.1%) had D-dimer, 39 (0.4%) had VQ and 347 (3.8%) patients had CTPA performed. 30-day outcomes included: 874 (9.6%) patients with any serious outcome; 0.9% deaths; and 818 (9.0%) patients with non-PE serious outcomes. Overall, 56 patients (prevalence 0.6%; 95% CI 0.5% 0.8%) were diagnosed with PE, including 8 (0.1%) of those admitted to hospital at the index presentation. Only 11 patients (0.1%) with a non-PE serious condition had a concomitant underlying PE identified. Conclusion: The prevalence of PE is very low among ED patients with syncope, including those hospitalized following syncope. While acknowledging syncope may be caused by an underlying PE, clinicians should be cautious against indiscriminate over-investigations for PE.
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