From the Guidelines
Diagnosing pulmonary embolism (PE) in pregnant women requires a modified approach, prioritizing maternal health while minimizing radiation exposure to the fetus, and the most recent guidelines recommend a step-wise approach starting with clinical assessment, D-dimer testing, and then imaging with ventilation-perfusion scan or CT pulmonary angiography as needed 1.
Diagnostic Approach
The diagnosis of PE in pregnant women begins with:
- Clinical assessment using validated tools like the modified Wells score or YEARS criteria to determine pretest probability
- D-dimer testing, though its interpretation is challenging due to naturally increasing levels during pregnancy
Imaging
If D-dimer is elevated or clinical suspicion remains high, imaging is necessary, starting with:
- Compression ultrasonography of the legs to look for deep vein thrombosis
- If negative and PE suspicion persists, a chest X-ray followed by ventilation-perfusion (V/Q) scan is preferred due to lower radiation exposure to the fetus compared to CT pulmonary angiography (CTPA)
- CTPA may be used when V/Q scan is unavailable or inconclusive
Anticoagulation
Throughout the diagnostic process, maternal health takes priority, and anticoagulation with low molecular weight heparin should be initiated promptly when PE is strongly suspected, even before the diagnosis is confirmed, unless contraindicated, as recommended by recent guidelines 1.
Key Considerations
- Maternal health takes priority due to the significant mortality risk of untreated PE
- Minimizing radiation exposure to the developing fetus is crucial
- The approach balances the need for accurate diagnosis with minimizing radiation exposure
- Recent guidelines provide a framework for diagnosing and managing PE in pregnant women, emphasizing the importance of a step-wise approach and consideration of maternal and fetal risks 1.
From the Research
Diagnostic Approach
To diagnose a pulmonary embolism (PE) in a pregnant woman, a combination of clinical assessment, laboratory tests, and imaging studies are used. The diagnostic approach involves:
- Clinical probability assessment to determine the likelihood of PE 2, 3
- D-dimer measurement to help exclude PE in patients with a low or intermediate pretest clinical probability 2, 3
- Venous compression ultrasonography of the lower limbs (CUS) to detect deep vein thrombosis 2, 3
- Computed tomography pulmonary angiography (CTPA) or ventilation-perfusion (V/Q) scan to confirm the diagnosis of PE 2, 4, 3
Imaging Studies
The choice of imaging study depends on the clinical scenario and the availability of resources. The options include:
- Chest radiography (CXR) as the first radiation-associated procedure 4
- Lung scintigraphy (V/Q scan) as the preferred test in the setting of a normal CXR 4
- CTPA rather than digital subtraction angiography (DSA) in a pregnant woman with a nondiagnostic V/Q result 4
- Ventilation perfusion scanning as the preferred initial test to detect pulmonary embolism within pregnancy 5
Diagnostic Algorithm
A diagnostic algorithm based on assessment of clinical probability, D-dimer measurement, CUS, and CTPA can safely rule out PE in pregnant women 3. The algorithm involves:
- Excluding PE in patients with a low or intermediate pretest clinical probability and a negative D-dimer result
- Performing lower limb CUS and CTPA in patients with a high pretest clinical probability or a positive D-dimer result
- Using a V/Q scan if CTPA results are inconclusive
Management
The management of PE in pregnancy involves anticoagulation with low molecular weight heparin for a minimum of 3 months in total duration and until at least 6 weeks postnatal 5. The treatment should be commenced on clinical suspicion and not be withheld until an objective diagnosis is obtained 5. A multidisciplinary team approach involving emergency physicians, pulmonologists, angiologist, cardiologists, thoracic and/or cardiovascular surgeons, radiologists, and obstetricians is recommended to choose a tailored management option including an interventional treatment 6.