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Three Part Question

In [pregnant women with suspected PE without symptoms and signs of DVT], which [imaging modality should be used] to [detect PE in the acute setting]?

Clinical Scenario

A 26 year old primigravida at 31 weeks gestation presents to the Emergency Department with shortness of breath and pleuritic chest pain. She is apyrexial, has a respiratory rate of 26, a heart rate of 110 and oxygen saturation of 95% on room air. There is no evidence of leg pain or swelling. Her ECG is normal and you are awaiting the report of her chest X-Ray. You suspect a pulmonary embolism (PE)- which imaging should you order next?

Search Strategy

PubMed- May 2018.

((((((v/q[Title/Abstract]) OR (Ventilation[Title/Abstract]) OR (SPECT[Title/Abstract]) OR (Perfusion[Title/Abstract]) OR (lung sca*[Title/Abstract]) OR (scintigraphy[Title/Abstract])) AND ((CTPA[Title/Abstract]) OR (computed tomography[Title/Abstract]) OR (pulmonary angiog*[Title/Abstract]) OR (CT[Title/Abstract])) AND ((pregnan*[Title/Abstract]) OR (gestatio*[Title/Abstract]) OR (obstetr*[Title/Abstract]) OR (antenatal[Title/Abstract])) AND (English[lang]) AND ("last 5 years"[PDat]) AND (Humans[Filter]))) NOT Review[Publication Type])) AND Full text[Filter]

Search Outcome

Twenty three papers were identified using the search strategy. Fourteen results were excluded due as they did not meet the inclusion criteria. One review article was incorrectly listed as a case report on PubMed. Eight papers met the final inclusion criteria.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Astani et al 2014 USA	53 pregnant patients with suspected PE	Retrospective analysis	Radiation doses	Pulmonary scintigraphy has a significantly lower effective and breast-absorbed dose when compared with CTPA. Fetal-absorbed dose for pulmonary scintigraphy has a lower dose (P=0.0010) when compared with CTPA, even when the ventilation component of pulmonary scintigraphy is performed.	Small sample size, retrospective design
Bajc et al	127 pregnant women with suspected PE	Retrospective analysis	Diagnosis of PE, radiation doses	The negative predictive value of V/P SPECT was high. For P SPECT, the calculated fetal absorbed dose was?	Retrospective design
Grüning et al 2016	168 patients who underwent diagnostic imaging for PE and a control group of 89 patients who underwent VQ SPECT	Retrospective analysis	Diagnosis of PE, imaging quality, radiation doses	V/P SPECT and CTPA provide a similar diagnostic yield for diagnosing PE during pregnancy, V/P SPECT has a lower effective dose and breast-absorbed dose.	Variation in scan timing, retrospective design
Isidoro et al 2017 Portugal	Site protocols	Protocol comparison	Radiation doses	Fetal-absorbed doses are similar for CTPA and V/P SPECT. The calculated dose to the breast was 1.3–10.6 times higher from CTPA compared to V/P SPECT.	No data on human sample
Moriarty et al 2015 USA	100 pregnant women with suspected PE	Retrospective analysis	Diagnosis of PE, alternate diagnoses	In pregnant women without PE on CTPA, potential alternative causes for patient symptoms were seen on CT in 12% of cases.	Unable to verify rate of PE, some undiagnostic cases, retrospective design
Parekh et al 2017 UK	190 pregnant patients	Retrospective analysis	Diagnosis of PE using V/P SPECT, negative predictive value	The positive rate, NPV and indeterminate rates of V/P SPECT in pregnant patients were 6.8, 100 and 2.3%, respectively.	Retrospective design, few outcomes reported
Perisinakis et al 2014 Greece	4 mathematic anthropomorphic phantoms representing pregnant women with different body sizes.	Computational model	Radiation doses	Pulmonary scintigraphy is associated with less radiation risk for an average-sized pregnant patient and her fetus. In CTPA, maternal BMI increases fetal-absorbed and effective dose. Pulmonary scintigraphy is comparatively more dose-efficient.	Small sample size, computerised model

Comment(s)

The RCOG green top guidelines recommend that in women with suspected PE without symptoms and signs of DVT, a ventilation/perfusion lung scan or a computerised tomography pulmonary angiogram (CTPA) should be performed. However, there is confusion and debate over which imaging modality is better. Eight recent original studies were identified which evidenced which modality to choose. The quality of evidence is variable, but there appears to be a consensus that, in pregnancy, pulmonary scintigraphy and CTPA provide a similar diagnostic yield for diagnosing PE. Pulmonary scintigraphy produces a significantly lower dose of breast-absorbed radiation than CTPA, which is associated with an increased lifetime risk of breast cancer. Arguably, pulmonary scintigraphy may also not pose an increased fetal-absorbed dose as previously thought, especially in the case of high maternal BMI. Importantly, the negative predictive value of pulmonary scintigraphy is high; two studies reported a NPV of 100% using V/P SPECT. CTPA has the potential advantages over pulmonary scintigraphy of being more readily available in the acute setting and the ability to diagnose other potential causes of symptoms in around 12% of cases, but these benefits should be balanced with the longer-term risks to the mother.

Clinical Bottom Line

When available, pulmonary scintigraphy should be prioritised over CTPA due to the lower dose of breast-absorbed radiation and comparable dose of fetal-absorbed radiation. However, where feasible, women should be involved in the decision-making process.

References

1. Armstrong, L Gleeson, F Mackillop, L Mutch, S Beale Survey of UK imaging practice for the investigation of pulmonary embolism in pregnancy.
2. Astani, Seyed A Davis, Leah C Harkness, Beth A Supanich, Mark P Dalal, Ishani Detection of pulmonary embolism during pregnancy: comparing radiation doses of CTPA and pulmonary scintigraphy.
3. Bajc, Marika Olsson, Berit Gottsater, Anders Hindorf, Cecilia Jogi, Jonas V/P SPECT as a diagnostic tool for pregnant women with suspected pulmonary embolism.
4. Gruning, Thomas Mingo, Rebecca E Gosling, Matthew G Farrell, Sally L Drake, Brent E Loader, Robert J Riordan, Richard D Diagnosing venous thromboembolism in pregnancy.
5. Isidoro, Jorge Gil, Paulo Costa, Gracinda Pedroso de Lima, Joao Alves, Caseiro Ferreira, Nuno C Radiation dose comparison between V/P-SPECT and CT-angiography in the diagnosis of pulmonary embolism.
6. Moriarty, John M Bolster, Ferdia O'Connor, Clare Fitzpatrick, Patricia Lawler, Leo P Kavanagh, Eoin C MacMahon, Peter J Murray, John G Frequency of nonthromboembolic imaging abnormalities in pregnant women referred for computed tomography pulmonary arteriography.
7. Parekh, Amit Graham, Richard Redman, Stewart Ventilation/perfusion single-photon emission computed tomography: a service evaluation.
8. Perisinakis, Kostas Seimenis, Ioannis Tzedakis, Antonis Damilakis, John Perfusion scintigraphy versus 256-slice CT angiography in pregnant patients suspected of pulmonary embolism: comparison of radiation risks.