What are the diagnostic criteria for pulmonary embolism (PE) on chest Computed Tomography (CT)?

From the Guidelines

Pulmonary embolism on chest CT should be diagnosed using validated diagnostic criteria, such as clinical probability assessment, D-dimer testing, and CT pulmonary angiography (CTPA), as recommended by the 2019 ESC guidelines 1. The diagnosis of pulmonary embolism (PE) is a critical task, as it can be life-threatening if left untreated. According to the 2019 ESC guidelines 1, the diagnostic strategy should be based on clinical probability, using either clinical judgement or a validated prediction rule.

• In suspected high-risk PE, bedside echocardiography or emergency CTPA should be performed for diagnosis, and intravenous anticoagulation with UFH should be initiated without delay.
• In suspected PE without haemodynamic instability, validated diagnostic criteria should be used, and anticoagulation should be initiated in case of high or intermediate clinical probability, while diagnostic workup is in progress.
• D-dimer testing should be used in outpatients/emergency department patients with low or intermediate clinical probability, or who are PE-unlikely, and a normal result can safely exclude PE in these patients.
• CTPA is the major diagnostic modality currently used, and a normal CTPA can safely exclude PE in patients with low or intermediate clinical probability, or who are PE-unlikely, as stated in the 2022 ACR Appropriateness Criteria 1. The 2022 ACR Appropriateness Criteria 1 also emphasize the importance of clinical scoring algorithms, such as the Wells criteria and the Geneva score, in diagnosing PE.
• The diagnostic challenge of PE is most commonly addressed with these algorithms, D-dimer testing, and specialized CT angiography (CTA).
• In hemodynamically stable patients with a low or intermediate clinical likelihood of PE, normal results on D-dimer testing can obviate the need for PE imaging.
• CT pulmonary angiography (CTPA) is commonly performed in patients with a high pretest probability for PE or in those with a positive D-dimer without a high-risk clinical score. It is essential to note that the diagnosis of PE requires immediate attention, as it can be life-threatening.
• The clots form due to Virchow's triad factors: blood stasis, hypercoagulability, and endothelial injury.
• Follow-up imaging may be necessary to ensure clot resolution, and patients should be evaluated for underlying causes such as immobility, cancer, or thrombophilia, as recommended by the 2008 ESC guidelines 1.

From the Research

Diagnosis of Pulmonary Embolism on Chest CT

• Pulmonary embolism (PE) is characterized by occlusion of blood flow in a pulmonary artery, typically due to a thrombus that travels from a vein in a lower limb 2
• The diagnosis is determined by chest imaging, and in patients with a high probability of PE, chest imaging should be performed without delay 2
• The clinical probability of PE can be assessed using a structured score or using clinical gestalt, and D-dimer testing can be used to exclude PE in patients with low or intermediate clinical probability 2

Treatment of Pulmonary Embolism

• Anticoagulation is the primary treatment for PE, and can be performed with unfractionated heparin (UFH), low molecular weight heparins (LMWH), or fondaparinux 3, 4
• Direct oral anticoagulants (DOACs) such as apixaban, edoxaban, rivaroxaban, or dabigatran are noninferior to traditional anticoagulation therapy and have a lower risk of bleeding 2, 5
• The decision on the duration of anticoagulation should consider both the individual risk of PE recurrence and the individual risk of bleeding, and extended anticoagulation with DOACs can reduce the risk of recurrent venous thromboembolism without increasing the rate of major bleeding 3, 6

Imaging Techniques

• Chest CT is a commonly used imaging technique for diagnosing PE, and can be used to evaluate the extent of the thrombus and the presence of any complications 2
• CT pulmonary angiography (CTPA) is a specific type of chest CT that can be used to diagnose PE, and has a high sensitivity and specificity for detecting thrombi in the pulmonary arteries 2

Patient Management

• Patients with PE should be managed in a multidisciplinary manner, with involvement of cardiologists, pulmonologists, and other specialists as needed 3, 4
• The management of PE should be individualized based on the patient's clinical presentation, medical history, and risk factors for recurrence and bleeding 3, 2