Should a pregnant patient with a suspected pulmonary embolism (PE) and an indeterminate computed tomography (CT) scan be empirically treated with anticoagulation therapy?

Management of Pregnant Patients with Indeterminate CT Scan for Pulmonary Embolism

In pregnant patients with suspected pulmonary embolism (PE) and an indeterminate CT scan, empiric anticoagulation therapy is strongly recommended while awaiting further diagnostic testing to prevent potentially fatal outcomes. 1

Initial Approach to Indeterminate CT Results

• For pregnant patients with suspected PE and an indeterminate CT pulmonary angiography (CTPA), further diagnostic testing rather than clinical management alone is recommended 1
• If the patient has a high clinical suspicion of PE and a low risk of bleeding, anticoagulant therapy should be initiated immediately while awaiting additional diagnostic test results 1
• Early anticoagulation in suspected PE has been associated with reduction in adverse outcomes including mortality 1

Diagnostic Algorithm When CTPA is Indeterminate

1. Assess for signs and symptoms of DVT:

   • If DVT symptoms are present, perform bilateral compression ultrasound (CUS) of lower extremities 1
   • If CUS is positive, initiate anticoagulation therapy 1
   • If CUS is negative, proceed with additional imaging 1

2. Consider lung scintigraphy (V/Q scan):

   • V/Q scanning is recommended in pregnant women with a normal chest X-ray 1
   • V/Q scanning has a similar false-negative rate to CTPA in pregnancy (0.5% vs 0.4%) 1

3. If V/Q scan is also non-diagnostic:

   • Further testing with repeat CTPA is recommended rather than clinical management alone 1
   • Technical improvements should be considered for repeat CTPA to increase diagnostic yield 1

Anticoagulation Management

• Low-molecular-weight heparin (LMWH) is the preferred anticoagulant for treatment of PE in pregnancy 2, 3
• Standard therapeutic dosing of LMWH should be initiated promptly when PE is suspected with an indeterminate scan and high clinical suspicion 1
• Treatment should be continued for at least 3 months, including 6 weeks postpartum 3, 4

Special Considerations

• Pregnancy physiological changes affect contrast dynamics during CTPA, which may contribute to indeterminate results 1

• Protocol optimization for pregnant patients includes:

  • Automated bolus triggering
  • High iodine flux (flow rate 4.5-6 ml/s)
  • High iodine concentration (350-400 mg I/ml)
  • Clear breathing instructions to minimize Valsalva effects 1

• For unstable patients with suspected high-risk PE, more aggressive interventions may be considered:

  • Thrombolysis may be appropriate in life-threatening situations 5
  • For women in peripartum or early postpartum period, non-fibrinolytic treatments may be preferred due to high bleeding risk 5

Rationale for Empiric Treatment

• PE is a leading cause of pregnancy-related mortality, accounting for 20% of maternal deaths in the United States 1
• The consequences of missing a PE diagnosis can be catastrophic, with high mortality rates 6, 7
• The risk-benefit ratio strongly favors treatment when diagnostic uncertainty exists, as untreated PE has significantly higher mortality than the bleeding risks of anticoagulation 1

Avoiding Common Pitfalls

• Do not rely solely on clinical assessment for diagnosis, as signs and symptoms of PE overlap with normal physiologic changes of pregnancy 1
• Avoid repeated radiation exposure through multiple imaging studies; optimize the first CTPA study with pregnancy-specific protocols 1
• Do not withhold anticoagulation while awaiting additional testing if clinical suspicion is high and bleeding risk is low 1
• Remember that technically inadequate CTPA studies occur in 6-36% of pregnant women, with suboptimal vascular opacification and respiratory motion artifact being common causes 1