Pulmonary embolism diagnosed in 17% of patients hospitalized for first episode of syncope

EBM Focus - Volume 11, Issue 44

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Reference - N Engl J Med 2016 Oct 20;375(16):1524

  • Pulmonary embolism (PE), a possible (though uncommon) cause of syncope, is not routinely assessed for in patients presenting with syncope.
  • A recent cross-sectional study explicitly assessed for PE with D-dimer blood testing, clinical assessment including the Wells score, and, if indicated, imaging in 560 adults hospitalized for first episode of syncope.
  • PE was detected on imaging in 17% of patients hospitalized for first episode of syncope. Although the clinical impact of PE in these patients is not known, it may be worth adding D-dimer blood tests and clinical assessments for PE to evaluations of patients being considered for hospitalization for syncope.

Syncope may be benign, but may require hospitalization if an underlying serious condition or increased mortality is suspected (Emerg Med Clin North Am 2016 Aug;34(3):601). Pulmonary embolism (PE) is considered to be a possible (though uncommon) cause, but most guidelines do not include an explicit assessment for PE as part of routine evaluation (Eur Heart J 2009 Nov;30(21):2631, Circulation 2006 Jan 17;113(2):316). To better assess the prevalence of PE in patients hospitalized for syncope, a recent cross-sectional study in Italy explicitly assessed for PE in addition to guideline-based syncope evaluations in 560 adults (mean age 76 years) hospitalized for first episode of syncope. Reasons for hospitalization included fall-related trauma, severe coexisting conditions, no clinically based explanation for syncope, or suspected cardiac cause of syncope. Patients presenting with syncope were excluded if they were not hospitalized, were pregnant, had previous episodes of syncope, or were having anticoagulation therapy. PE was ruled out in patients who had a negative D-dimer blood test and had a low clinical risk for PE (no more than 4 points on the Wells score, based on history and physical). Patients who had a positive D-dimer test and/or high clinical risk for PE also had imaging with computed tomographic pulmonary angiography or, if they were allergic to the contrast agent, a ventilation-perfusion lung scan.

All 560 patients had a D-dimer blood test and a clinical assessment for PE with the Wells score, and PE was ruled out based on these tests in 330 patients (58.9%). The remaining 230 patients had a positive D-dimer test and/or a high clinical risk for PE, and so were further assessed with imaging. PE was detected on imaging in 97 patients (17.3% of the entire cohort; 42.2% of the 230 patients who had imaging). Of these 97 patients, 63% had imaging characteristics suggestive of PE as the etiology for the syncope episode (location in main pulmonary or lobar artery or perfusion defect > 25% of the area of both lungs). Of note, 24.7% of the 97 patients with PE on imaging did not have signs or symptoms often associated with PE, such as tachypnea, tachycardia, hypotension, or signs of deep vein thrombosis. In further analysis of the entire cohort, 205 patients did not have a clinically based explanation for syncope, while 355 patients did (neural, orthostatic hypotension, or cardiac). The rate of PE on imaging was 25.4% in patients who did not have a clinically based explanation for syncope compared to 12.7% in patients who did.

This cross-sectional study showed that PE detected on imaging is not rare in adults hospitalized for first episode of syncope, particularly in adults with a positive D-dimer blood test, a high clinical risk for PE, and/or lacking a clinically based explanation for syncope. It is important to emphasize that the results of this study apply to adults hospitalized for first episode of syncope, but not necessarily to any person who presents with syncope. In fact, an additional 2,024 patients presenting for syncope were excluded because they were not admitted to the hospital, had previous syncope episodes, or met other exclusion criteria. It is also important to emphasize that the emboli were detected on imaging; the evidence assessing the clinical impact of PE discovered with imaging is limited, and a clinical follow-up of the patients in this study was not conducted. Therefore, it is not known if the addition of an explicit assessment for PE improves clinical outcomes, or if it improves current tools that estimate the risk for serious outcomes in patients with syncope, such as the San Francisco Syncope Rule. However, a D-dimer blood test and clinical assessment for PE would not add substantial time or effort to the evaluation of patients being considered for hospitalization for syncope, and so may be worth considering for these patients.

For more information, see the Syncope evaluation, Pulmonary embolism (PE), and Suspected pulmonary embolism - initial evaluation and management topics in DynaMed Plus. DynaMed users click here.


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