Pulmonary embolism
Updates to Article Attributes
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
Iodinatediodinated oil pulmonary embolism- metallic
Mercurymercury pulmonary embolism - amniotic fluid embolism
- cement embolism: comprised of PMMA
- catheter embolism
- septic pulmonary embolism
Pathology
Risk factors
- primary hypercoagulable states
- recent surgery
- pregnancy
- prolonged bed rest
/immobility/ immobility - malignancy
- oral contraceptive use
Clinical assessment
Pre‐test probability scores are intended to replace empirical assessment of patients with suspected pulmonary embolism:
The ECG may show a S1Q3T3 pattern.
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's sign: regional oligaemia and highest positive predictive value (10%)
- pleural effusion (35%)
- knuckle sign 11
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
’shump- 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%
CTPACT
Acute pulmonary emboli
WillCT pulmonary angiography (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.
Chronic pulmonary emboli
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 8
- 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 8
- CT features suggestive of right ventricular dysfunction include 8
-
right ventricular dysfunction
- subacute-to-chronic emboli
-<li><a href="/articles/iodinated-oil-pulmonary-embolism">Iodinated oil pulmonary embolism</a></li>-<li><a href="/articles/metallic-mercury-pulmonary-embolism">metallic Mercury pulmonary embolism</a></li>- +<li><a href="/articles/iodinated-oil-pulmonary-embolism">iodinated oil pulmonary embolism</a></li>
- +<li><a href="/articles/metallic-mercury-pulmonary-embolism">metallic mercury pulmonary embolism</a></li>
-<li>prolonged bed rest/immobility</li>- +<li>prolonged bed rest / immobility</li>
-</ul><p>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 <sup>4</sup>. </p><h4>Radiographic features</h4><p>Depends to some extent on whether it is <a href="/articles/acute-pulmonary-embolism">acute</a> or <a href="/articles/chronic-pulmonary-embolism">chronic</a>. Overall has a predilection for the lower lobes.</p><h5>Plain film</h5><h6>Described chest radiographic signs include:</h6><ul>- +</ul><p>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 <sup>4</sup>. </p><h4>Radiographic features</h4><p>Depends to some extent on whether it is <a href="/articles/acute-pulmonary-embolism">acute</a> or <a href="/articles/chronic-pulmonary-embolism">chronic</a>. Overall has a predilection for the lower lobes.</p><h5>Plain film</h5><p>Described chest radiographic signs include</p><ul>
-<a title="Knuckle sign" href="/articles/knuckle-sign-1">Knuckle sign</a> <sup>11</sup>- +<a href="/articles/knuckle-sign-1">knuckle sign</a> <sup>11</sup>
-</ul><p><strong>Sensitivity and specificity of chest x-ray signs</strong> <sup>1</sup>:</p><ul>- +</ul><p>Sensitivity and specificity of chest x-ray signs <sup>1</sup></p><ul>
-<li>Hampton’s hump<ul>- +<li>Hampton hump<ul>
-</ul><h5>CTPA</h5><p>Will show filling defects within the pulmonary vasculature with acute pulmonary emboli. When observed in the axial plane this has been described as the <a href="/articles/polo-mint-sign">polo mint</a> sign. The central filling defect from the thrombus is surrounded by a thin rim of contrast, appearing like the popular sweet, the <a href="http://en.wikipedia.org/wiki/Polo_(confectionery)">polo mint</a> <sup>9</sup>.</p><p>Features noted with <strong><a href="/articles/chronic-pulmonary-emboli">chronic pulmonary emboli</a></strong> include:</p><ul>- +</ul><h5>CT</h5><h6>Acute pulmonary emboli</h6><p>CT pulmonary angiography (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 <a href="/articles/polo-mint-sign">polo mint</a> sign. The central filling defect from the thrombus is surrounded by a thin rim of contrast, appearing like the popular sweet, the <a href="http://en.wikipedia.org/wiki/Polo_(confectionery)">polo mint</a> <sup>9</sup>.</p><h6>Chronic pulmonary emboli</h6><p>Features noted with <a href="/articles/chronic-pulmonary-emboli">chronic pulmonary emboli</a> include</p><ul>
References changed:
- 11. Williams J & Wilcox W. Pulmonary Embolism. Roentgenographic and Angiographic Considerations. Am J Roentgenol Radium Ther Nucl Med. 1963;89:333-42. - <a href="https://www.ncbi.nlm.nih.gov/pubmed/14000892">Pubmed</a>
- 11.Williams JR, Wilcox WC. Pulmonary embolism: roentgenographic and angiographic considerations. AJR Am J Roentgenol. 1963; 89:333.
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