In a 21-week pregnant woman with increased shortness of breath, what other signs of pulmonary embolism (PE) should be looked for and when is more than an echocardiogram (echo) necessary?

Evaluating Shortness of Breath in a 21-Week Pregnant Woman: Signs of PE and Imaging Beyond Echocardiography

In a 21-week pregnant woman with shortness of breath, you should look for pleuritic chest pain, tachycardia, hypoxemia, hemoptysis, and syncope as additional signs of pulmonary embolism (PE), and imaging beyond echocardiography is necessary when these warning signs are present or when there is a high clinical suspicion despite a normal echocardiogram. 1, 2

Key Warning Signs of PE in Pregnancy

When evaluating a pregnant woman with shortness of breath at 21 weeks, look for these specific PE indicators:

• Primary symptoms:

  • Pleuritic chest pain (55% of confirmed PE cases) 1
  • Persistent dyspnea that doesn't resolve with rest 2
  • Cough (24% of confirmed PE cases) 1
  • Sweating (18% of confirmed PE cases) 1

• Critical signs requiring immediate attention:

  • Tachycardia
  • Hypoxemia (check oxygen saturation and arterial blood gases)
  • Abnormal alveolar-arterial gradient (>15 mm Hg) 1, 2
  • Hemoptysis
  • Syncope or unexplained hypotension 1

When to Move Beyond Echocardiography

An echocardiogram alone is insufficient for diagnosing PE in pregnancy. Further imaging is necessary when:

1. Warning signs are present - Any of the above symptoms, especially in combination
2. Abnormal echocardiogram findings - Right ventricular dysfunction or pulmonary hypertension
3. Normal echocardiogram but high clinical suspicion - As echocardiogram can be normal in non-massive PE

Diagnostic Algorithm for Suspected PE

1. First step: Chest radiograph (CXR) - This is the recommended first radiation-associated procedure 1, 2

   • Low radiation exposure to fetus
   • Helps rule out other causes of dyspnea

2. If CXR is normal:

   • Proceed to lung scintigraphy (V/Q scan) rather than CT pulmonary angiography (CTPA) 1

3. If CXR is abnormal:

   • Proceed directly to CTPA 1

4. If leg symptoms are present:

   • Perform bilateral venous compression ultrasound of lower extremities first 1
   • If positive, begin anticoagulation
   • If negative, proceed with the imaging algorithm based on CXR results

5. D-dimer testing is NOT recommended:

   • Poor specificity (15%) and inadequate sensitivity (73%) in pregnancy 1, 2
   • Negative D-dimer does not reliably exclude PE in pregnancy

Important Pitfalls to Avoid

• Misattribution bias - Don't assume shortness of breath is always physiological in pregnancy 2
• Diagnostic anchoring - Consider PE even when other conditions seem more likely 2
• Radiation concerns - Don't avoid necessary imaging; properly performed diagnostic tests pose minimal risk to the fetus 2
• Relying on clinical features alone - No single clinical feature or combination reliably predicts PE in pregnancy 1
• Delaying diagnosis - PE remains a leading cause of maternal mortality; prompt diagnosis and treatment are essential 3

Special Considerations

• The absence of pleuritic chest pain has a negative predictive value of 97.8% for PE in pregnancy 3
• Smoking and the presence of multiple risk factors significantly increase PE risk in pregnancy 3
• In cases of confirmed PE with hemodynamic instability, consider specialized interventions including thrombolytic therapy in severe cases 2, 4

Remember that PE is a leading cause of maternal mortality, and symptoms of normal pregnancy (shortness of breath, tachycardia, leg swelling) overlap with PE symptoms, making diagnosis challenging. Therefore, a low threshold for appropriate imaging is justified when PE is suspected.