What is the workup for shortness of breath in a 24-week pregnant patient?

Workup for Shortness of Breath at 24 Weeks Pregnant

The workup for shortness of breath in a 24-week pregnant patient should begin with assessment for life-threatening causes while recognizing that physiologic changes of pregnancy peak at 24-26 weeks with up to 50% increase in plasma volume, increased cardiac output, and compensatory heart rate increase that can exacerbate underlying conditions. 1

Initial Assessment

History

• Assess severity and timing of symptoms:
  • Persistent excessive shortness of breath that doesn't resolve with rest (emergency warning sign) 1
  • Onset (sudden vs. gradual)
  • Exacerbating factors (exertion, position, time of day)
  • Associated symptoms (chest pain, palpitations, dizziness, edema)

Physical Examination

• Vital signs: BP, HR, RR, oxygen saturation (maintain normal saturations) 1
• Cardiac: Murmurs, gallops, JVD
• Pulmonary: Wheezing, crackles, decreased breath sounds
• Lower extremities: Edema, signs of DVT
• Obstetric: Uterine tenderness, contractions

Diagnostic Testing

First-Line Tests

• Chest radiography (CXR) - first radiation-associated procedure 2
• ECG
• Complete blood count
• Basic metabolic panel
• D-dimer (interpret with caution as levels normally increase in pregnancy)
• Oxygen saturation monitoring

Second-Line Tests (Based on Initial Findings)

• If PE suspected:

  • Follow pregnancy-adapted YEARS algorithm with D-dimer 2
  • If CXR normal and PE still suspected: V/Q scan preferred over CTPA due to lower maternal breast radiation exposure 2

• If cardiac cause suspected:

  • Echocardiography (to evaluate for peripartum cardiomyopathy, structural heart disease) 1
  • NT-proBNP (elevated in heart failure but also in pre-eclampsia without cardiac abnormality) 1

• If respiratory cause suspected:

  • Pulmonary function tests
  • Arterial blood gas (if severe symptoms)

Differential Diagnosis

Physiologic Causes

• Normal pregnancy-related dyspnea (most common)
• Anemia of pregnancy

Cardiac Causes

• Peripartum cardiomyopathy (can present during pregnancy or postpartum) 3
• Pre-existing or pregnancy-induced hypertension/pre-eclampsia 1
• Valvular heart disease exacerbated by pregnancy

Pulmonary Causes

• Pulmonary embolism (leading cause of pregnancy-related mortality) 2
• Asthma exacerbation
• Pneumonia

Other Causes

• Pulmonary edema (can occur as complication of pre-eclampsia without cardiac impairment) 1
• Anxiety

Management Approach

1. Stabilize if acute distress:

   • Oxygen therapy to maintain normal saturations 1
   • Position patient in left lateral decubitus position to relieve IVC compression

2. Diagnose underlying cause:

   • Start with least invasive tests
   • Proceed to imaging as needed (CXR first, then V/Q scan if PE suspected) 2

3. Treat specific cause:

   • If PE suspected: Start LMWH while awaiting diagnostic confirmation 2
   • If cardiac cause: Multidisciplinary team approach with cardiology 1
   • If asthma: Continue usual asthma medications 1

Warning Signs Requiring Immediate Attention

• Persistent excessive shortness of breath not resolving with rest
• Severe chest pain
• Oxygen saturation <95% on room air
• Altered mental status
• Syncope or near-syncope
• Signs of right heart failure 1

Key Considerations

• Pregnancy itself increases risk of venous thromboembolism 2
• Physiologic changes peak at 24-26 weeks gestation (when this patient presents) 1
• Shortness of breath during normal pregnancy can be associated with subtle cardiac findings that may suggest cardiac involvement 4
• Maintain high index of suspicion for cardiomyopathy in pregnant patients with shortness of breath 1

Remember that shortness of breath is common in normal pregnancy but can also be the first sign of serious underlying conditions that require prompt diagnosis and management to optimize maternal and fetal outcomes.