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Emerg Med J 30:251-252 doi:10.1136/emermed-2013-202363.3
  • Best evidence topic reports

BET 2: Imaging for the diagnosis of pulmonary embolism in pregnant women

Abstract

A short-cut review was carried out to establish whether CT pulmonary angiography (CTPA) or ventilation–perfusion (VQ) scanning offer advantages in imaging the pregnant woman with a possible deep vein thrombosis. A total of 80 papers was found using the reported search, of which four represented the best evidence to answer the clinical question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these best papers are tabulated. The clinical bottom line is that a ventilation-perfusion (or perfusion) scan should be prioritised if the chest x-ray is normal. In the case of an abnormal chest x-ray, a CT pulmonary angiography scan will be better in finding an alternative diagnosis.

Report by: Simon Bordeleau, Emergency Medicine PGY-4

Institution: Laval University, Quebec, Canada

Three-part question

In (Pregnancy with pulmonary embolism), is (Computed-Tomographic pulmonary angiography better than Ventilation (V)–Perfusion (Q) scintigraphy) for (detection of pulmonary embolism)?

Clinical scenario

A 27-year-old woman presents to the emergency department with shortness of breath. She is 26 weeks pregnant. The lower limbs Doppler ultrasound is negative. You must perform another diagnostic test to eliminate a pulmonary embolism (PE). You wonder which test is the most appropriate for this patient: a CTPA or a VQ scintigraphy.

Search strategy

No bestBETs or critical appraisal was found on this topic.

Embase via NHS Evidence date of search 09/01/2013

  • #1 pregnancy’/exp OR pregnancy

  • #2 pulmonary AND (\\\'embolism\\\’/exp OR embolism)

  • #3 (#1 AND #2)

  • #4 computed tomographic angiography\\\’/exp OR \\\'computed tomographic angiography\\\’

  • #5 (#3 AND #4)

  • #6 \\\'ventilation\\\’/exp OR ventilation AND (\\\'perfusion\\\’/exp OR perfusion)

  • #7 (#5 AND #6) 29 (73 records)

From this review, two were relevant

Medline via the Pubmed interface search date 09/01/2013

  • #1 Pregnancy:

  • #2 Pulmonary embolisms:

  • #3 Computed-tomographic angiography:

  • #4 Ventilation perfusion:

  • #1 and #2: #1 and #2 and #3:

  • #1 and #2 and #3 and #4: (7 records)

From this review, three were relevant

The Cochrane Library issue 12 of 12 2012

MeSH descriptor: (Pulmonary Embolism) explode all trees AND MeSH descriptor: (Pregnancy) explode all trees 1 article 0 relevant

Search outcome

A total of four unique resources was found relevant, and are shown in table 2.

Table 2

Relevant paper(s)

Comment(s)

These four retrospective studies looked at the diagnostic performance of CTPA and lung scintigraphy. The CT scanners were 64-multidetector row (Ridge, Revel), four to 16-multidetector row (Cahill) or eight to 64-multidetector rows (Shahir). The lung scintigraphy protocol used in Ridge and Shahir was perfusion only and a perfusion/ventilation protocol was used in Revel and Cahill. The irradiation on breast tissue is higher with CT than scintigraphy (8×). The fetal irradiation is minimal with both tests. Even if CT is better than lung scintigraphy in normal patients, the haemodynamic changes in pregnant women make CT angiography less optimal for PE detection, even with state-of-the-art CT technology. Timing with perfusion protocol can be hard to synchronise. Only one study (Ridge) found a statistical difference in favour of lung scintigraphy compared to CT angiography in pregnant woman with suspected PE. These two tests yield approximately the same diagnostic percentage in the three other studies. We should give priority to the test that causes less harm to the patient. The choice of test may also depend on the possibility of an alternative diagnosis for shortness of breath (if abnormal chest x-ray), in which CT angiography is better but with a higher breast cell irradiation. The American Thoracic Society also leans towards this avenue in their 2011 expert recommendations.

Clinical bottom line

For the diagnosis of PE in pregnancy, if imaging is needed, a VQ (or perfusion) scan should be prioritised if the chest x-ray is normal. In the case of an abnormal chest x-ray, a CTPA scan will be better in finding an alternative diagnosis.

▸ Ridge CA, McDermott S, Freyne BJ, et al. Pulmonary embolism in pregnancy: comparison of pulmonary CT angiography and lung scintigraphy. Am J Roentgenol 2009;193:1223–7.

▸ Cahill AG, Stout M, Macones GA, et al. Diagnosing pulmonary embolism in pregnancy using computed-tomographic angiography or ventilation–perfusion. Obstet Gynecol 2009;114:124–129.

▸ Shahir K, Goodman LR, Tali A, et al. Pulmonary embolism in pregnancy: CT pulmonary angiography versus perfusion scanning. AJR 2010;195:W214–20.

▸ Revel MP, Cohen S, Sanchez O, et al. Pulmonary embolism during pregnancy: diagnosis with lung scintigraphy or CT angiography? Radiology 2011;258:590–8.

Footnotes

  • Provenance and peer review Commissioned; internally peer reviewed.


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Poll

Among patients with minor TBI (GCS 13-15) getting CT scans ≥ 24 hours after injury, what proportion have a traumatic finding?

Results

0.5% - 43% response rate
3% - 41% response rate
10% - 16% response rate

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