Even among the 355 patients thought to have had a different cause for syncope, an embolism was detected in 45 (12.7%, 95% CI: 9.2 to 16.1).

“Not surprisingly, patients with dyspnea, tachycardia, hypotension, or clinical signs or symptoms of deep-vein thrombosis were more likely to have pulmonary embolism, as were those with active cancer. However, the proportion of patients who did not have these features yet had an objective confirmation of pulmonary embolism was not negligible,” the Prandoni team found.

Ultimately, no definitive cause of the syncope was found in 205 of the 560 patients.

Dr. Prandoni told Reuters Health in an email that, based on the results, “All existing guidelines dealing with the diagnostic work-up of patients hospitalized for syncope should be rapidly reconsidered, and the execution of a diagnostic work-up for pulmonary embolism should be strongly encouraged in all such patients, including those in whom there is an apparent explanation for the episode of syncope.”

Because pulmonary embolism “is a serious and potentially lethal complication that can be treated effectively and safely with the available antithrombotic drugs, its prompt detection is crucial,” he said. “In addition, the cost of the additional diagnostic workup for pulmonary embolism is acceptably low.”