Clot or not: What are we going to do about PESIT?


    Clot or not: What are we going to do about PESIT?

    In October 2016, the Pulmonary Embolism in Syncope Italian Trial (PESIT) was published in the New England Journal of Medicine. Since its publication, it has generated a great deal of conversation and controversy.


    First, a brief rundown of the study:

    Its objective was to determine the prevalence of PE among patients older than 18 who were hospitalized for a first episode of syncope. Patients with previous syncopal episodes, those on anticoagulation therapy, or those who were pregnant were excluded. After eliminating patients who were excluded or did not consent, 560 admitted patients were included in the study. Each had a d-dimer and was evaluated with the Wells Score. Patients with a negative d-dimer and a low Wells Score (330 patients in all) were deemed to be low-risk for PE and had no further PE work-up. The other 230 patients had either CTA or ventilation-perfusion scanning. Of those tested, 97 had a confirmed PE. That’s 17.3% of the admitted cohort, and 42.2% of the admitted patients who were deemed high-risk enough to be tested.


    17.3% – that’s almost one in six! Do we need to CTA everyone who presents for syncope?

    No! Let’s look more closely at the data.

    • Remember that only admitted patients were evaluated for PE in this trial. During the study period, only 3.8% of all patients who visited the ED for syncope had a PE – that’s a lot less than 17.3%.
    • The characteristics that were significantly different between the admitted patients who had PE and those who did not (previous VTE, undetermined cause of syncope, RR > 20, HR > 100, SBP < 110, clinical signs of DVT, active cancer) would prompt us to consider PE anyway.
    • Finally, of the 72 PEs confirmed by CTA, 24 were segmental or sub-segmental. In these vessels, 25-50% of positive studies are actually false positives. Even if the PE is real, the clinical significance of a clot in one of these small vessels is unknown. Anticoagulation comes with its own serious risks – we don’t want to increase someone’s risk of ICH or other bleeding for a PE that doesn’t have any physiologic effect, or worse, that isn’t there at all.


    Some final thoughts:
    This study was well-run, but it’s easy to misunderstand its conclusions. PE should be on your differential diagnosis in a patient who syncopizes. However, if your careful history and physical exam are inconsistent with PE, don’t feel compelled to search for it based solely on this research.



    1. Prandoni P, Lensing AWA, Prins M, et al. Prevalence of pulmonary embolism among patients hospitalized for syncope. N Engl J Med. 2016;375(16):1524-31.


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