What is the first step in the workup for a 32-week pregnant patient with a history of pulmonary embolism (PE) who presents with shortness of breath and tachycardia?

Diagnostic Approach for Suspected Pulmonary Embolism in a Pregnant Patient with History of PE

For a 32-week pregnant patient with shortness of breath, tachycardia, and history of PE, the first step in workup should be a chest X-ray followed by appropriate imaging based on the CXR results, with compression ultrasound of lower extremities considered if signs/symptoms of DVT are present.

Initial Assessment and Risk Stratification

• In a pregnant patient with suspected PE, especially with a history of previous PE, a structured diagnostic approach is essential as PE is a leading cause of pregnancy-related mortality in developed countries 1
• The patient's presentation with shortness of breath for one week, tachycardia (HR 104), but normal oxygen saturation (98%) requires prompt evaluation, particularly given her history of PE after tummy tuck 1
• Despite normal oxygen saturation, tachycardia in a pregnant patient with previous PE history should raise suspicion for recurrent PE 1

Diagnostic Algorithm for Pregnant Patients

Step 1: Clinical Assessment

• Evaluate for signs and symptoms of DVT (unilateral leg swelling, pain) as this would guide the initial diagnostic approach 1
• If signs/symptoms of DVT are present, bilateral compression ultrasound (CUS) of lower extremities should be performed first 1

Step 2: Chest X-Ray

• A chest X-ray should be the first radiation-associated procedure in the imaging workup for suspected PE in pregnancy 1
• This is a strong recommendation based on the need to minimize radiation exposure while determining the next appropriate imaging test 1

Step 3: Further Imaging Based on CXR Results

• If CXR is normal: Lung scintigraphy (V/Q scan) is recommended as the next imaging test rather than CTPA 1
• If CXR is abnormal: CTPA is recommended as the next imaging test 1

Important Considerations for Pregnant Patients

• D-dimer testing is not recommended to exclude PE in pregnant women as pregnancy normally increases D-dimer levels, leading to false positives 1
• Modern imaging techniques for PE diagnosis during pregnancy expose the fetus to radiation doses well below thresholds associated with complications (50-100 mSv) 1
• Both V/Q scan and CTPA are considered safe during pregnancy when properly performed 1

Management Considerations

• If PE is confirmed, low-molecular-weight heparin (LMWH) is the treatment of choice during pregnancy 1
• NOACs (novel oral anticoagulants) are contraindicated during pregnancy 1
• Anticoagulant treatment should be administered for at least 6 weeks after delivery with a minimum overall treatment duration of 3 months 1

Potential Pitfalls and Caveats

• Avoid delaying diagnosis due to concerns about radiation exposure, as untreated PE poses a greater risk to both mother and fetus 1
• Be aware that physiologic changes of pregnancy (increased heart rate, dyspnea) can mimic PE symptoms, making diagnosis challenging 1
• If CTPA is performed, modern techniques can significantly reduce radiation exposure to maternal breast tissue without compromising diagnostic quality 1
• If lung scintigraphy is non-diagnostic, further testing (typically CTPA) is recommended rather than clinical management alone 1

Following this systematic approach will ensure appropriate and timely diagnosis while minimizing unnecessary radiation exposure to both mother and fetus.