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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.

Author Year # of pt Techniques Sensitivity Specificity
Meanly 1997 30 3D G 87% 97%
Gupta 1999 36 3D Gd 85% 96%

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