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Although pulmonary embolism (PE) occasionally presents with syncope, patients with syncope are not always evaluated systematically for PE. In this prospective study from Italy, researchers determined the prevalence of PE in 560 adults (mean age, 76) who were hospitalized for first episodes of syncope; pregnant women and patients taking anticoagulants were excluded. Each patient underwent D-dimer testing and Wells score calculation (in addition to standard syncope work-up); those with positive D-dimer results or high-probability Wells scores underwent pulmonary computed tomography (CT) angiography or ventilation-perfusion lung scanning.
Either D-dimer results or Wells scores were positive in 230 patients (41%), and 97 of these patients (17% of the entire cohort) had PE. PE was diagnosed in 25% of patients without another explanation for syncope but also in 13% of patients with other potential explanations. A high thrombotic burden was not universal in patients with PE and syncope; for example, 33% of patients whose PE was confirmed by CT angiography had no emboli proximal to segmental or subsegmental arteries.
Prandoni P et al. Prevalence of pulmonary embolism among patients hospitalized for syncope. N Engl J Med 2016 Oct 20; 375:1524. (http://dx.doi.org/10.1056/NEJMoa1602172)
Comment
At first glance, the 17% prevalence of PE among patients with syncope seems remarkable. However, this finding is less surprising given that the study included only hospitalized patients with first syncopal episodes. In addition, because the thrombotic burden was not extensive in some patients, PE might not have directly caused the syncopal episode in every case in which it was detected. Nevertheless, for patients similar to those included in this study (and who are high-risk or have elevated D-dimer), the findings support systematic evaluation for PE.