Review Question - QID 218741

This pregnant patient who presents with acute onset pleuritic chest pain, dyspnea, hypoxemia, and signs of right heart strain on EKG (S1Q3T3 pattern) likely has an acute pulmonary embolism (PE). Pregnant patients with suspected PE and a normal chest radiograph should undergo a ventilation/perfusion (V/Q) scan for further diagnostic evaluation.

Pregnancy is a hypercoagulable state that is a significant risk factor for venous thromboembolism (VTE). In pregnancy, pulmonary embolism (PE) can present with dyspnea, pleuritic chest pain, cough, sweating, and hemoptysis. The diagnostic algorithm for PE in pregnant patients differs from that of general patients in order to reduce radiation exposure. In patients with suspected PE in pregnancy and leg symptoms (such as pain, swelling, or erythema), initial evaluation should include a compression ultrasound of the lower extremities. Otherwise, patients with suspected PE should undergo a chest radiograph. For patients with a normal chest radiograph, a V/Q scan should be performed. Patients with an abnormal chest radiograph or who have a nondiagnostic V/Q scan should undergo a CTPA. If VTE or a PE is diagnosed by any of these modalities, treatment in pregnancy is usually with subcutaneous heparin in stable patients and thrombolytic therapy in patients with life-threatening PE.

The American College of Obstetricians and Gynecologists (ACOG) reviewed thromboembolism in pregnancy. The authors found that V/Q scanning has high diagnostic accuracy in patients with a normal chest radiograph. Therefore, the authors recommend the initial use of V/Q scanning over CTPA in pregnant patients with suspected pulmonary embolism.

Incorrect Answers:
Answer 1: Compression ultrasonography of the lower extremities is usually not indicated unless clinical examination demonstrates signs and symptoms of deep vein thrombosis such as leg pain, swelling, or erythema.

Answer 2: Computed tomography pulmonary angiography (CTPA) is a highly sensitive and specific test for the diagnosis of pulmonary embolism. However, due to the higher radiation exposure from a CTPA, V/Q scanning is the preferred initial test in pregnant patients. Nonetheless, a CTPA should be performed in pregnant patients with an abnormal initial chest radiograph or with an indeterminate V/Q scan.

Answer 3: D-dimer levels have limited utility in the diagnosis of PE in pregnancy. There is elevation of D-dimer levels during normal pregnancy. Therefore, this test has poor sensitivity and specificity in pregnancy.

Answer 4: Magnetic resonance pulmonary angiography (MRPA) can be used to evaluate for PE; however, the sensitivity and specificity of this test during pregnancy have not been evaluated. In addition, teratogenicity from prolonged exposure to gadolinium has been observed in animal (but not human) studies.

Bullet Summary:
The best test to evaluate for pulmonary embolism after a chest radiograph in a pregnant patient is a ventilation/perfusion (V/Q) scan to limit radiation exposure.