What are the American College of Obstetricians and Gynecologists (ACOG) recommendations for diagnosing pulmonary embolism (PE) in pregnancy?

ACOG Recommendations for Pulmonary Embolism Diagnosis in Pregnancy

The American Thoracic Society and Society of Thoracic Radiology recommend a diagnostic algorithm for suspected pulmonary embolism (PE) in pregnancy that begins with chest radiography as the first radiation-associated procedure, followed by lung scintigraphy (V/Q scan) if the chest X-ray is normal, or CT pulmonary angiography (CTPA) if the chest X-ray is abnormal. 1, 2

Clinical Assessment

• Clinicians should maintain a high index of suspicion for PE in pregnant women, as normal pregnancy can mimic some PE symptoms 1, 2
• Common presenting symptoms include dyspnea (62%), pleuritic chest pain (55%), cough (24%), and sweating (18%) 1
• No validated clinical prediction rules (like Wells or Geneva criteria) exist specifically for determining pre-test probability of PE in pregnant patients 1, 2
• D-dimer testing should not be used to exclude PE in pregnancy due to poor specificity and reports of false negatives in pregnant women with documented PE 1

Diagnostic Algorithm

Initial Approach

• For pregnant women with suspected PE and signs/symptoms of deep venous thrombosis (DVT):

  • Perform bilateral venous compression ultrasound (CUS) of lower extremities 1, 2
  • If CUS is positive, initiate anticoagulation treatment 1
  • If CUS is negative, proceed with chest radiography 1

• For pregnant women with suspected PE without signs/symptoms of DVT:

  • Proceed directly to studies of the pulmonary vasculature rather than CUS 1

Imaging Sequence

1. Chest Radiography (CXR) should be the first radiation-associated procedure for all pregnant women with suspected PE 1, 2

   • This helps triage between lung scintigraphy and CTPA

2. If CXR is normal:

   • Perform lung scintigraphy (V/Q scan) rather than CTPA 1, 2
   • V/Q scanning delivers lower radiation dose to maternal breast tissue (0.98-1.07 mGy vs. 10-60 mGy with CTPA) 1

3. If CXR is abnormal:

   • Perform CTPA rather than lung scintigraphy 1, 2
   • CTPA provides better diagnostic yield and can identify alternative diagnoses 2

4. If V/Q scan is nondiagnostic:

   • Further diagnostic testing is recommended rather than clinical management alone 1
   • CTPA is recommended rather than digital subtraction angiography (DSA) 1

Radiation Considerations

• Fetal radiation doses from properly performed diagnostic tests present no measurably increased risk of prenatal death, malformation, or impairment of mental development 1
• Maternal breast tissue radiation exposure is significantly higher with CTPA compared to V/Q scanning 2
• A 25-year-old woman undergoing a single CTPA has an estimated lifetime relative risk of radiation-induced breast cancer of 1.011 2

Special Considerations

• Technically inadequate CTPA studies occur in 6-36% of pregnant women due to suboptimal vascular opacification and respiratory motion artifacts 2
• For unstable patients or when studies are not available promptly, empiric anticoagulation should be considered while awaiting diagnostic results 2
• PE remains a leading cause of maternal mortality in developed countries, contributing to approximately 2 deaths per 100,000 live births annually 3

Treatment Considerations

• Once PE is diagnosed, anticoagulation should be initiated with either unfractionated heparin or low molecular weight heparin 4
• Intravenous heparin is preferred around delivery due to its short half-life 4
• Warfarin is generally avoided during pregnancy due to potential adverse effects on the fetus 4