Pulmonary Embolism Causes <1% of Syncope, Study Confirms


Rarity of lung clots contradicts PESIT data

Researchers confirmed in a retrospective study that pulmonary embolism is unlikely to cause syncope that results in a trip to the emergency room.

Fewer than 1% of nearly 1.7 million patients treated at emergency departments for syncope had pulmonary embolism, according to databases from Canada, Denmark, Italy, and the U.S., reported Giorgio Constantino, MD, of Italy’s Ospedale Maggiore Policlinico in Milan, and colleagues.

Pulmonary embolism was responsible for syncope in just 0.06% to 0.55% of those cases, they wrote in JAMA Internal Medicine; among those admitted, PE was the cause in 0.15% to 2.10%.

“Pulmonary embolism was rarely identified in patients with syncope. Although pulmonary embolism should be considered in every patient, not all patients should undergo evaluation for pulmonary embolism,” the authors concluded. “The unnecessary exposure to radiation and the risk of contrast allergy is significant. Furthermore, the false-positive rate of tests, such as the D-dimer assay and computed tomographic pulmonary angiograms, is high, leading to more tests and overdiagnosis and including risks of unnecessary anticoagulation.”

“Pulmonary embolism has always been considered an uncommon cause of syncope,” according to Constantino’s group. The new data confirm this belief and fly in the face of the PESIT study, which estimated the prevalence of pulmonary embolism to be as high as 3.7% in patients going to the emergency department with syncope.

Still, no studies so far have been perfect.

“Because PESIT used a structured algorithm to assess for the presence of pulmonary embolism, one could hypothesize that previous studies, as well as clinical practice, might have underestimated pulmonary embolism prevalence. Even in the present study, some pulmonary embolism diagnoses could have been missed because they were not suspected, and therefore no information relevant to pulmonary embolism was reported in the administrative data,” the investigators acknowledged.

To identify as many cases of pulmonary embolism as possible, they determined the prevalence of lung clots at 90-day follow-up (assuming they were also there at emergency department arrival) and determined it lay in the 0.14%-0.83% range of all those who fainted and went to the emergency room (or 0.35%-2.63% of the hospitalized subset).

“Even in this case, pulmonary embolism was identified in less than 1% of patients, suggesting that, even if some pulmonary embolism had been missed at first evaluation, most were not clinically relevant,” Constantino and colleagues emphasized.

The findings make it hard to justify initiating standard diagnostic algorithms for pulmonary embolism in every syncope patient, they concluded.

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