Imaging pulmonary embolism in pregnancy: what is the most appropriate imaging protocol?

Abstract

Pulmonary embolism is the leading cause of death in pregnancy. Despite the difficulties in clinical diagnosis and the concerns regarding radiation of the fetus, the British Thoracic Society guidelines for imaging pulmonary embolism do not specifically address the issue of imaging for pulmonary embolism in this group. This communication discusses the difficulties of diagnosis and imaging pulmonary embolism in pregnancy and proposes a suitable imaging protocol. Clinical exclusion of patients from further imaging is recommended if the patient has a low pre-test probability of pulmonary embolism and a normal d-dimer. It is advised that all remaining patients undergo bilateral leg Doppler assessment. If this test is positive, the patient should be treated for pulmonary embolism; if negative, all patients should be referred for CT pulmonary angiography. Ideally, informed consent should be obtained prior to CT scanning. All neonates exposed to iodinated contrast in utero should have their thyroid function tested in the first week of life due to the theoretical risk of contrast induced hypothyroidism.

Managing acute collapse in pregnant women

“…In one study, only 2% had a high probability scan result. 23,25,[29][30][31]33,[38][39][40][41] The follow-up of untreated women after a normal or low probability scan showed no adverse effects. A normal scan will exclude PE and a high probability scan has a positive predictive value of 85 to 90% but the sensitivity is only 41% with a specificity of 97%.…”

“…25,31,38 When the pretest clinical probability of a PE is low the finding of a low probability VQ scan is as reliable as a CT angiogram to exclude a pulmonary embolism, and a high clinical probability and a high probability VQ scan is enough evidence to start treatment with a positive predictive value of 85 to 90%. 23,31,35,38 If the clinical probability of PE is high and the VQ scan is not diagnostic further investigations should be done to exclude the diagnosis. 23,25,29 Venous compression duplex ultrasound (VCUS).…”

“…23,25,29 Venous compression duplex ultrasound (VCUS). VCUS is indicated in patients with a high clinical probability of PE with other risk factors such as leg symptoms 29,30,33,38,40 and it is especially useful in women less than 20 weeks gestation. The sensitivity is 95% with specificity of 96% to diagnose proximal DVT.…”

“…31,42 If the VCUS is positive, treatment can be initiated for PE as long as the test was correctly performed. 26,38 Serial follow-up VCUS can also be valuable in excluding patients with PE. 30 Computer tomography pulmonary angiography (CTPA).…”

Peripartum pulmonary embolism: Anesthetic and surgical considerations

“…The rate of pulmonary embolism (PE) in the peripartum period is fivefold higher in comparison to the same aged non-pregnant female [2]. This increased risk of peripartum pulmonary embolism (PPE) is a combined effect of hypercoagulability, venous stasis and vascular injury.…”