Prospective Study of Pulmonary Embolism Presenting as Syncope

Background: Syncope represents a common condition among the general population. It is also a frequent complaint of patients in the emergency department (ED). Pulmonary embolism (PE) considers a differential diagnosis, particularly in a case of syncope without chest pain. Study Question: What is the prevalence of PE among patients who presented an episode of syncope to the ED and among those hospitalized for syncope in a tertiary care hospital? Study Design: From January 2012 to December 2017, we conducted a prospective observational study among adult patients presenting themselves to the ED consecutively or admitted for syncope. Measures and Outcomes: Syncope and PE were defined by professional guidelines. PE was ruled out in patients who had a low pretest clinical probability, as per Wells score and a negative D-dimer assay. In other patients, computed tomography pulmonary angiography was performed. Results: Seventeen thousand eight-two patients (mean age 71.3 +/- 13.24 years) visited the ED for syncope. PE was detected in 45 patients (mean age 65.75 6 +/- 9.45 years): 4 with low risk, 26 with intermediate risk, and 15 with high risk. The prevalence of PE in those hospitalized with syncope was 11.47%, which is 45 of 392 (confidence interval 95% 8.48-15.04), and was 2.52%, 45 of 1782 (confidence interval 95% 1.8-3.3), in patients presenting with syncope to the ED. The location of the embolus was bilateral in 24 patients (53.33%), in a main pulmonary artery in 10 (22.22%), in a lobar artery in 10 (22.22%), and in a segmental artery in 1 (2.22%). Conclusions: The occurrence of syncope, if not explained otherwise, should alert one to consider PE as a differential diagnosis. PE rate, presenting as syncope, is the highest in patients with large thrombi, which is responsible for bilateral or proximal obstruction in a main or lobar pulmonary artery.