Clinical relevance of syncope in patients with pulmonary embolism

Background: Syncope is an unusual clinical manifestation of pulmonary embolism (PE), and the clinical significance of syncope in PE patients remains controversial. We investigated the incidence of syncope, examined the clinical factors associated with syncope, and assessed the association between syncope and the short-term outcomes of PE. Methods: We retrospectively classified patients presenting with PE into 2 groups: patients with syncope and those without syncope. We compared the clinical and computed tomography parameters between the groups. Results: Among 1084 patients diagnosed with PE, 45 (4.2%) presented with syncope. Four patients which presented with cardiac arrest were excluded from the study. The syncope group showed significantly higher blood biomarker levels and higher rates of central PE and right ventricular dilation than the control group. Unprovoked PE (odds ratio [OR] 8.046, 95% confidence interval [CI] 3.073-21.069, p < 0.001), female sex (OR 3.419, 95% CI 1.348-8.675, p=0.010), central PE (OR 2.854, 95% CI 1.298-6.278, p=0.009), and troponin I level (OR 2.812, 95% CI 1.765-4.480, p < 0.001) were observed to be independent factors associated with syncope in PE patients. However, multivariate analysis showed that the presence of syncope was not a significant predictor of adverse outcomes and recurrent venous thromboembolism in PE patients. Conclusions: Although syncope is associated with a more severe form of PE, it does not influence the short-term prognosis of PE. Central PE, blood troponin I level, unprovoked PE, and female sex were observed to be clinical factors related with syncope in patients with PE.