What are the guidelines for managing a pregnant patient with suspected pulmonary embolism (PE) presenting with symptoms of dyspnea, tachycardia, and near-syncope?

Management of Suspected Pulmonary Embolism in Pregnant Patients

Pregnant patients with suspected pulmonary embolism presenting with symptoms like dyspnea, tachycardia, and near-syncope should undergo immediate diagnostic workup starting with chest radiography, followed by lung scintigraphy if the CXR is normal or CT pulmonary angiography (CTPA) if the CXR is abnormal, while initiating anticoagulation therapy promptly during the diagnostic process. 1

Initial Assessment and Risk Stratification

• The modified Wells score with a cutoff of ≥6 points is the most appropriate scoring system for evaluating suspected PE in pregnancy 1
• Dismissing PE symptoms in pregnant patients because they overlap with normal pregnancy symptoms is considered negligent medical practice, as PE remains one of the leading causes of maternal death in high-income countries 1
• A history of DVT significantly increases PE risk during pregnancy (odds ratio 9.4) and should be incorporated into risk assessment 1

Diagnostic Algorithm

1. First Step: Chest Radiography

   • Chest radiography (CXR) should be performed as the first radiation-associated procedure in pregnant women with suspected PE 2, 1
   • This is a strong recommendation despite low-quality evidence 2

2. If DVT symptoms are present:

   • Perform bilateral compression ultrasound of lower extremities to potentially avoid radiation exposure 2, 1
   • If positive, initiate anticoagulation treatment
   • If negative, proceed with further testing 2

3. If no DVT symptoms or negative ultrasound:

   • With normal CXR: Perform lung scintigraphy (V/Q scan) 2, 1
   • With abnormal CXR: Perform CT pulmonary angiography (CTPA) 1
   • CTPA is preferred over digital subtraction angiography for nondiagnostic V/Q results 2

4. Radiation Considerations:

   • V/Q scan: Maternal breast radiation 0.98-1.07 mGy; Lung tissue 5.7-13.5 mGy
   • CTPA: Maternal breast radiation 10-60 mGy; Lung tissue 39.5 mGy
   • Fetal radiation exposure with CTPA is minimal (0.003-0.02 mSv) 1

Treatment Approach

• Initiate anticoagulation promptly while diagnostic workup is ongoing, unless active bleeding or absolute contraindications exist 1
• Low molecular weight heparin (LMWH) is the preferred agent during pregnancy 1, 3
• Unfractionated heparin (UFH) is typically used in high-risk PE, especially peri-partum 1, 4
• Continue anticoagulation until PE is definitively ruled out 1
• NOACs (non-vitamin K antagonist oral anticoagulants) should not be used during pregnancy 1

Management of Hemodynamically Unstable Patients

• Perform bedside echocardiography immediately to assess for right ventricular dysfunction 1
• In cases of high-risk PE with hypotension and shock, thrombolysis may be considered despite significant bleeding risks 1, 3
• For massive or submassive PE, a multidisciplinary approach involving maternal-fetal medicine specialists is recommended 1

Important Caveats and Pitfalls

• D-dimer levels continuously increase during pregnancy, with levels above the VTE 'rule-out' threshold in almost one-quarter of pregnant women in the third trimester, limiting its utility 1
• The American Thoracic Society suggests that D-dimer not be used to exclude PE in pregnant women 2
• Cesarean section increases PE risk 20-fold compared to vaginal delivery 1
• Avoid diagnostic closure and consider other causes for the patient's presentation, as symptoms of PE (tachycardia, tachypnea, shortness of breath) overlap with common pregnancy complaints 3, 5, 6

Patient Education

• Educate patients on PE symptoms including pleuritic chest pain, cough, and sweating
• Emphasize the importance of seeking immediate medical attention if these symptoms occur 1
• Advise stopping physical activity immediately and consulting healthcare providers if symptoms develop 1

This diagnostic algorithm was formulated assuming patients are stable and all studies are equally available. In unstable situations or when studies are not available promptly, empiric anticoagulation therapy and/or alternate diagnostic strategies should be considered 2.