Diagnosis and Management of Pulmonary Embolism

Current Concepts:
Blocking of the pulmonary artery by foreign matter such as a blood clot, fat, air, tumor tissue.
The third most common cause of death in hospitalized patients.
Most patients with DVT develop PE (Majority of cases are unrecognized clinically).
Untreated, approximately 1/3 of patients who survive an initial PE die of a future embolic episode.

Frequency:
In the US:
  • 60% of patients who died in hospitals had PE.
    The diagnosis was missed in up to 70%.
Prospective studies demonstrated DVT in:
  • 10-13% of all medical patients placed on bed rest for 1 week,
  • 29-33% of all patients in medical ICUs,
  • 20-26% of patients with pulmonary diseases who stays at bed for ≥3 days,
  • 27-33% of those admitted to a critical care unit after MI,
  • 48% of patients who are asymptomatic after CABG.
Pathphysiology of PE:
  • VIRCHOW’S TRIAD
    Local trauma to vessel wall
    Hypercoagulability
    Stasis
  • Hypercoagulable state
    Inherited (Primary)
    Secondary (Acquired)
  • Primary Hypercoagulable states
  • Acquired Hypercoagulable states

Non-imaging Diagnostic Methods:
  • PLASMA D-DIMER ELISA
    • Natural Break down of fibrin to D-Dimers
    • Sensitive but not specific as it
    • Increases in MI, repsis, cancer, any other systemic
  • ABG
    • No difference between average PaO2 in patients with and without PE
    • Not part of diagnostic strategy
  • ECG
    • Exclude AMI
    • Raise suspicion of PE
    • Confirm the diagnosis

Imaging Diagnostic Methods:
  • CXR
    • Abnormal CXR in ¼ of patients.
    • Focal oligemia (Westermark’s sign) indicates massive central embolic occlusion.
    • Peripheral wedge shaped density above the diaphragm (Hampton’s hump) indicates pulmonary infarction.
    • Small pleural effusion.

Spiral or the new multi-detector CT:
  • Replacing V/Q scan
  • Replacing pulmonary Angio in Dx
  • More specific, more accessible
  • Provides alternative diagnosis in 30% of cases
  • May miss sub segmental emboli
  • Give information about the size and function of RV
  • Requires a high dose of injected contrast (can use non iodinated contrast) - check creatinine
  • Diagnostic even in the presence of an abnormal chest radiograph

Ventilation-Perfusion scan:
  • Perfusion scan:
    • Technetium 99m-labeled macro aggregated albumin (MAA).
    • injected intravenously.
  • Ventilation scan:
    • Technetium 99m DTPA aerosol.
    • Inhaled.
  • Second choice imaging test.
  • 70% of patients have an indeterminate result and need another test to make the diagnosis.
  • Good in the presence of a normal chest radiograph.
  • Not helpful in the presence of an abnormal chest radiograph, in patients with COPD or cardiac disease.
  • Does not provide an alternative diagnosis.

Pulmonary angiography:
  • Was the Gold standard, replaced by the new multidetector CT scanning
  • Invasive - catheter inserted into femoral vein, up the IVC through into right-sided cardiac chambers and into pulmonary arteries.
  • Contrast injected directly into pulmonary arteries.
  • Required when interventions are planned as:
    • Suction catheter embolectmy.
    • Mechanical clot fragmentation.
    • Catheter directed thrombolysis.

With MRA:
Keep your tablets in the pack in which they were supplied.
Keep your tablets below 30°C.
Keep your tablets in a safe place where children cannot see or reach them.

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