Acute pulmonary embolism

Posted By Wael Nemattalla
Acute pulmonary embolism

35 years old female with dyspnea and left renal angle pain.

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  • Wael Nemattalla 2014-02-24 10:55:30

    Pulmonary embolism





    A pulmonary embolism (PE) refers to embolic occlusion of the pulmonary arterial system. The majority of cases result from thrombotic occlusion and therefore the condition is frequently termed pulmonary thrombo-embolism which is what this article mainly covers.



    Other embolic sources include



    air embolism

    fat embolism

    tumour embolism - comprised of tumour thrombus

    hydatid pulmonary embolism

    talc pulmonary embolism

    Iodinated oil pulmonary embolism

    metallic Mercury pulmonary embolism

    amniotic fluid embolism

    cement embolism - comprised of PMMA

    catheter embolism

    septic pulmonary embolism





    Pathology



    Risk factors



    primary hypercoagulable states

    protein C deficiency

    antithrombin III

    lupus anticoagulant

    recent surgery

    pregnancy

    prolonged bed rest / immobility

    malignancy

    oral contraceptive use



    Clinical assessment



    Pre‐test probability scores are intended to replace empirical assessment of patients with suspected pulmonary embolism:



    Wells score

    Geneva score

    Serological tests



    D-Dimer (ELISA)



    Commonly used as a screening test in patients with a low and moderate probability clinical assessment, on these patients:



    normal D-dimer has almost 100% negative predictive value (virtually excludes PE) - no further testing is required

    raised D-dimer is seen with PE but has many other causes and is therefore non-specific; it indicates the need for further testing if pulmonary embolism is suspected 4

    On patients with a high probability clinical assessment, a D-dimer test is not helpful because a negative D-dimer result does not exclude pulmonary embolism in more than 15%. Patients are treated with anticoagulants while awaiting the outcome of diagnostic tests 4.



    Radiographic features



    Depends to some extent on whether it is acute or chronic. Overall has a predilection for the lower lobes.



    Plain film



    Described chest radiographic signs include



    Fleishner sign - enlarged pulmonary artery (20%)

    Hampton hump - peripheral wedge of airspace opacity and implies lung infarction (20%)

    Westermark sign - regional oligaemia and highest positive predictive value (10%)

    pleural effusion (35%)

    Sensitivity and specificity of chest x-ray signs 1



    Westermark sign



    sensitivity: ~ 14 %

    specificity: ~ 92% %

    positive predictive value: ~ 38 %

    negative predictive value: ~ 76 %



    vascular redistribution



    sensitivity: ~ 10 %

    specificity: ~ 87 % %

    positive predictive value: ~ 21 %

    negative predictive value: ~ 74 %



    Hampton’s hump



    sensitivity: ~ 22 %

    specificity: ~ 82 %

    positive predicitve value: ~ 29 %

    negative predictive value: ~ 76 %



    pleural effusion



    sensitivity: ~ 36 %

    specificity: ~ 70 %

    positive predictive value: ~ 28 %

    negative predictive value: ~ 76 %



    elevated diaphragm



    sensitivity: ~ 20 %

    specificity: ~ 85 %

    PPV: ~ 30 %

    NPV: ~ 76 %



    CTPA



    Will show filling defects within the pulmonary vasculature with acute pulmonary emboli. When observed in the axial plane this has been described as the 'polo mint' sign. The central filling defect from the thrombus is surrounded by a thin rim of contrast, appearing like the popular sweet, the polo mint 9.



    Features noted with chronic pulmonary emboli include



    webs or bands, intimal irregularities 3

    abrupt narrowing or complete obstruction of the pulmonary arteries 3

    “pouching defects” which are defined as chronic thromboemboli organised in a concave shape that “points” toward the vessel lumen 3

    Nuclear medicine - VQ scan



    Will show ventilation-perfusion mismatches. A high probability scan is defined as showing two or more unmatched segmental perfusion defects acccording to the PIOPED criteria.



    Complications



    acute emboli

    pulseless electrical activity in the context of a large obstructing saddle embolus

    acute or chronic emboli

    right ventricular dysfunction



    CT features suggestive of right ventricular dysfunction include

    abnormal position of the interventricular septum

    inferior vena caval contrast reflux



    RVD (right ventricular diameter):LVD (left ventricular diameter) ratio > 1 on reconstructed four chamber views



    * a RVD:LVD ratio > 1 on standard axial views is not considered to be good predictor of right ventricular dysfunction.

    sub acute to chronic emboli

    pulmonary infarction

    pulmonary hypertension

    pulmonary arterial sclerosis

    chronic cor pulmonale

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