Pulmonary embolism: MRI angiography could diagnose and exclude PE.

Clinical bottom line (level 2b)

  1. A third of patients with a suspected pulmonary embolism had one.
  2. A positive MRI scan diagnosed pulmonary embolism (LR+22) .
  3. A negative MRI scan may be able to rule out pulmonary embolism (LR-0.0) .
  4. A tenth of the scans needed to be repeated due to breathing artefacts.
Meaney et al: New England Journal of Medicine 1997; 336 (20): 1422-1427
Expires September 2003

The study

Setting: teaching hospital, USA

30 patients (aged range 22 to 83 years; mean 52, 50% male) referred for pulmonary angiography

Excluded if
  • MRI contraindication
  • mechanical ventilation



    • Independent blinded reference standard, applied in all patients from a consecutive inappropriate spectrum.
    Reference standard:
    • positive pulmonary angiogram within in 24 hours. Three independent interpreters blinded to test results.
    Diagnostic test: MRI: Gadolinium enhanced scan: imaging time 27 seconds. Patient held breath during scan. Positive diagnosis if intravascular filling defect

    The evidence

    pre-test probability of pulmonary embolism: 27%, (95% CI: 11% to 43%)

    diagnostic test pulmonary embolism no pulmonary embolism LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    MRI positive 8 1 22
    (3.2 to 150)     		89% 0.0
    (0.0 to 0.32)     		0.0%
    total 8 22

    observers 1+2: 0.64
    observer 1+3: 0.57
    observers 2+3: 0.83
    • There were three uncertain scans (10%) due to breathing artefact.

    Comments

    1. Better than ventilation-perfusion scans - faster, easier, ?fewer contrast problems.
    2. Uncertain how different radiologists, less used to reading these scans, would be able to interpret pictures.

    Citation

    1. Meaney JF, Weg JG, Chenevert TL, et al: diagnosis of pulmonary embolism with magnetic resonance angiography. New England Journal of Medicine 1997; 336 (20): 1422-1427
    Search Terms: hand search
    Contributor: Chris Ball and Clare Wotton, Unknown Month 2000
    Reviewer:

    Clinical Question.
    Patient suspected PE
    Intervention or Exposure MRI scan
    Outcome diagnosis