Bottom Line: A blood clot in the lungs was rarely identified in patients who went to the emergency department after fainting.
Why The Research Is Interesting: Fainting (known as syncope) is a common symptom people can experience. A blood clot in the lungs (known as a pulmonary embolism or PE) has been recognized as a serious cause of syncope but data are scant and the evidence is conflicting on how frequent that is the case.
Who and When: More than 1.6 million adults who went to an emergency department for syncope in five databases in four countries (Canada, Denmark, Italy and the United States); data collected from 2010 to 2016
What (Study Measures): Frequency of PE at emergency department and hospital discharge identified by diagnosis codes (primary outcome)
How (Study Design): This was an observational study. Researchers were not intervening for purposes of the study and they cannot control all the natural differences that could explain the study findings.
Authors: Giorgio Costantino, M.D., of the Fondazione Instituto di Ricovero e Cura a Carattere Scientifico Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy, and coauthors
Results: The frequency of PE diagnosis ranged from 0.06 percent to 0.55 percent of all patients who went to the emergency department for syncope; among hospitalized patients, the frequency ranged from 0.15 percent to 2.10 percent.
Study Limitations: The main limitation is using administrative data to identify patients with syncope and PE because patients can be missed.