Diagnostic Approach for Suspected Pulmonary Embolism

Clinical Presentation and Diagnostic Criteria

The American College of Radiology recommends CT pulmonary angiography (CTPA) as the most appropriate next step in evaluation for patients with high clinical suspicion for pulmonary embolism, with a rating of "usually appropriate" (7/9) according to the ACR Appropriateness Criteria 1, 2
Recent knee replacement surgery is a major risk factor for venous thromboembolism, and patients with this history are at increased risk of pulmonary embolism 3, 4
Sudden onset of chest pain and shortness of breath, tachycardia, and hypoxemia are clinical features that strongly suggest pulmonary embolism, particularly in patients with recent surgery or symptoms of deep vein thrombosis 2, 5
The presence of multiple high-risk features, including recent major surgery, tachycardia, hypoxemia, and symptoms of possible deep vein thrombosis, indicates a high pretest probability for pulmonary embolism 3, 4

CTPA is the preferred initial imaging modality for diagnosing pulmonary embolism in hemodynamically stable patients with high clinical suspicion, due to its high sensitivity and specificity 1, 2
Lower extremity ultrasound alone is insufficient as the initial test, as a negative result would not exclude pulmonary embolism, and clinical signs suggesting deep vein thrombosis should be further evaluated with CTPA 2, 5
Ventilation-perfusion (V/Q) scanning is an alternative when CTPA is contraindicated, but is less preferred as the initial test in patients with high clinical suspicion for pulmonary embolism 2, 6
Early initiation of anticoagulation should be considered while awaiting imaging results, given the high clinical suspicion for pulmonary embolism, and treatment with therapeutic anticoagulation should be initiated promptly if CTPA confirms the diagnosis 5, 8