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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References 

1. 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
2. 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
3. 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
4. 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