Syncope is a well-known initial manifestation of pulmonary embolism (PE)1. However, given the varied causes of syncope, determining the prevalence of PE among patients hospitalized for syncope is important.
A multicenter prospective study2 enrolled 560 patients not already on anticoagulation who were hospitalized for a first episode syncope. Of patients who had either a high pretest probability for PE, positive D-dimer assay or both, PE was diagnosed in 17%, or nearly 1 of 6 of enrolled patients, based on CT or ventilation/perfusion scan. PE was found more frequently among patients with syncope of undetermined cause than those with an alternative explanation (25.4% vs 12.7%).
Another multicenter prospective study (2019), however, found a much lower prevalence of PE (0.6%) among patients evaluated in the ED for syncope, including those who were not hospitalized.3 A related commentary on the article reported a prevalence of 4.1% in the total study population, assuming a “worst-case scenario calculation.” 4
Given these divergent results, perhaps the best advice is to consider PE as cause of syncope in the proper context and minimize overtesting when suspicion remains low.
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- Thames MD, Alpert JS, Dalen JE. Syncope in patients with pulmonary embolism. JAMA 1977;238:2509-2511. https://www.ncbi.nlm.nih.gov/pubmed/578884
- Prandoni P, Lensing AWA, Prins MH, et al. Prevalence of pulmonary embolism among patients hospitalized for syncope. N Engl J Med 2016;375:1524-31. http://www.nejm.org/doi/full/10.1056/NEJMoa1602172
- Thiruganasambandamoorthy V, Sivilotti MLA, Rowe BH, et al. Prevalence of pulmonary embolism among emergency department patients with syncope: a multicenter prospective cohort study [published online January 25, 2019]. Ann Emerg Med. doi:10.106/j.annemergmed.2018. https://www.annemergmed.com/article/S0196-0644(18)31535-X/fulltext
- Anonymous. Pulmonary embolism uncommon in syncope hospitalizations. Pulmonology Advisor. February 6, 2019. https://www.pulmonologyadvisor.com/pulmonary-embolism-uncommon-in-syncope-hospitalizations/printarticle/832069/
Contributed in part by Rebecca Berger MD, Department of Medicine, Mass General Hospital, Boston, MA