Respiratory medicine for MRCP Part 2

A 24-year-old woman presents with pleuritic chest pain and breathlessness. She is 8 weeks pregnant. Heart rate 108, oxygen saturation 96% on air, blood pressure 118/74 mmHg. Chest radiograph is normal and leg examination is unremarkable. What is the most appropriate next investigation?

1. D-dimer to decide whether imaging is needed Wrong. D-dimer rises physiologically in pregnancy, so a raised result does not discriminate and the validated rule-out algorithms are not applicable in the standard way.
2. CT pulmonary angiography or a ventilation–perfusion scan, after discussion of the relative radiation exposures correct Correct. Definitive imaging is required, the risk of a missed pulmonary embolism in pregnancy far exceeds the radiation risk of either test. CTPA delivers a higher maternal breast dose, V/Q a higher fetal dose; both are within accepted limits and the choice is made with the patient.
3. Empirical anticoagulation with no imaging at any stage Wrong as a definitive plan. Treatment dose anticoagulation is often started while imaging is arranged, but committing a young woman to months of therapy plus implications for future pregnancies without a diagnosis is not acceptable.
4. Bilateral leg ultrasound alone Insufficient. A positive scan would justify anticoagulation without further imaging, but a negative scan in a symptomatic patient does not exclude pulmonary embolism, and her legs are asymptomatic.
5. Echocardiography to look for right heart strain Wrong as the diagnostic test. It is useful in the haemodynamically unstable patient for risk stratification, but a normal echo does not exclude PE and she is stable.

The point: Pregnancy does not change the need to diagnose pulmonary embolism, it changes the conversation about how. D-dimer is unhelpful. Treat with low molecular weight heparin, not warfarin and not a DOAC.

Source: RCOG Green-top Guideline 37b — Thromboembolic disease in pregnancy and the puerperium RCOG · tier 2, specialty society or college