Prospective Study of Pulmonary Embolism Presenting as Syncope

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.

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?

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.

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.

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 ± 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%).

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.