EBQ:Prevalence of Pulmonary Embolism among Patients Hospitalized for Syncope

complete Journal Club Article
Paolo Prandoni, M.D., Ph.D., Anthonie W.A. Lensing, M.D., Ph.D., Martin H. Prins, M.D., Ph.D., Maurizio Ciammaichella, M.D., Marica Perlati, M.D., Nicola Mumoli, M.D., Eugenio Bucherini, M.D., Adriana Visonà, M.D., Carlo Bova, M.D., Davide Imberti, M.D., Stefano Campostrini, Ph.D., and Sofia Barbar, M.D.. "Prevalence of Pulmonary Embolism among Patients Hospitalized for Syncope". NEJM. 2016. (375):1524-1531.
PubMed Full text PDF

Clinical Question

What is the prevalence of pulmonary embolism in patients admitted for first time syncope? [1]


"Pulmonary embolism was identified in nearly one of every six patients hospitalized for a first episode of syncope."

Major Points

  • although PE is classically listed in the differential diagnosis of syncope, its prevalence is not well characterized
  • patients admitted for syncope with non-low probability uniformly evaluated by imaging, regardless of clinical suspicion
    • moderate/high risk as characterized by Wells and D-dimer

Study Design

  • multicenter: 11 Italian hospitals
  • cross-sectional study of consecutive patients
  • scanned within 48 hours of admission
  • enrolled patients polled
    • autonomic activation symptoms: diaphoresis, pallor, nausea
    • known syncope risk factors: cardiac history, dehydration, bleeding, medication changes
    • DVT/PE symptoms and risk factors
  • D-dimer obtained in all patients admitted
  • CT:PA or V-Q scan for all dimer(+) or moderate-high risk per Wells


  • Italian patients admitted to 11 hospitals (both academic and non-academic) for new syncope

Patient Demographics

  • mean age 76 (75% 70 years old or older)

Inclusion Criteria

  • syncope defined as a transient LOC
    • rapid onset
    • short:<1 minute
    • spontaneous resolution
  • met admission criteria
    • trauma from fall
    • severe coexisting conditions
    • no obvious cause of syncope
    • high probability of cardiac syncope, per Evaluation of Guidelines in Syncope Study score

Exclusion Criteria

  • "obvious" non-syncopal LOC
    • epileptic seizure
    • stroke
    • head trauma
  • previous syncope
  • anti-coagulated
  • pregnant


PE prevalence

  • 2584 patients in initial assessment
    • 1867 discharged
      • 829 likely vasovagal
      • 465 situational syncope (micturation or post-prandial)
      • 380 likely drug-induced hypotension
      • 112 volume depleted
      • 81 declined hospitalization
  • 717 admitted
    • 157 excluded
      • 118 anticoagulated
      • 82 afib
      • 36 "other reasons"
      • 35 repeat syncope
      • 4 declined
  • 560 enrolled
    • 330 low Wells (<4.0) and negative D-dimer
  • 230 high Wells (95) or low pretest with positive D-dimer (135)
  • 97 confirmed pulmonary embolism on CT or VQ (97/560=17.3%)

====Significant demographic/clinical characteristics by odds ratio++++

  • 14.20: signs of DVT
  • 10.80: tachypnea (RR>20)
  • 2.55: tachycardia (>100bpm)
  • 2.83: previous DVT/PE
  • 2.34: no alternative syncopal cause (cardiac structural disease, arrhythmia, volume depletion, drug-mediated, vasovagal)
  • 2.21: active cancer
  • 1.90: hypotension (SBP<110mmHg)

Thrombotic Burden

  • on CT (72)
    • 41.7% main pulmonary artery
    • 25% lobar
    • 26.4% segmental
    • 6.9% subsegmental
  • on VQ (24)
    • 16.7% >50% lung area
    • 33.3% 26-50% lung area
    • 50% 1-25% lung area
  • on autopsy (1)
    • both main pulmonary arteries

Primary Outcome

  • prevalence of PE in first time syncope admitted to hospital: 17.3%, or one in 6

Additional Observations

  • 25% patients w/ undetermined cause of syncope had PE
    • 13% patients with alternative explanations had PE
  • not all positive PE patients had significant clot burden on imaging (67% lobar or higher, 50%>25% lung area)
    • could smaller emboli cause syncope by stimulating transient arrhythmia while passing through R heart?
  • consistently 15-20% PE across all 11 centers
  • involved only patients hospitalized for first time syncope: denominator much larger if including ambulatory or discharged patients
  • imaging not performed in the excluded group; cannot speak for PE prevalence in these people

Criticisms & Further Discussion

  • headline-grabbing prevalence: 1/6 patients hospitalized for syncope have PE
    • how should we use this to change our testing for PE in syncope patients in the ED?
  • no causality established: consider that 40% of the emboli found on imaging are considered smaller than expected to cause significant cardiac output depression
    • should you scan for emboli that may be incidental and not causative of the syncope?
      • any affect on morbidity/mortality? Will be exposed to risks of anticoagulation regardless of whether PE is symptomatic.
      • patient will be subjected to PE workup every time they present for any myriad symptoms including dyspnea, chest pain, syncope
  • consider the included population was only 21.7% of the patients presenting for syncope 560/2584, with most patients discharged or excluded
    • 3.75% (97/2584) of all syncopes presenting on initial presentation found to have PE on imaging
  • consider that the admission criteria for these 11 hospitals may be different than where you work
    • if you admit more than 28% of first time syncopal patients, how will empiric PE imaging affect your resources
    • the admitted patient cohort are higher risk than many patients admitted in U.S. for syncope
      • mean age 76
      • many had signs/symptoms of PE/DVT and would have been imaged before admission in U.S. EDs
  • very well-designed trial, but limitations to its generalizability are in the details

External Links


See Also

Pulmonary Embolism Syncope Wells Criteria



  1. Prandoni P, Lensing AW, Prins MH, Ciammaichella M, Perlati M, Mumoli N, Bucherini E, Visonà A, Bova C, Imberti D, Campostrini S, Barbar S; PESIT Investigators. Prevalence of Pulmonary Embolism among Patients Hospitalized for Syncope. N Engl J Med. 2016 Oct 20;375(16):1524-1531. PubMed PMID: 27797317.