The Bottom Line: CT pulmonary angiography is becoming the standard of care for evaluating patients with suspected pulmonary embolism. For acute PE that manifests as complete arterial occlusion, the affected artery may be enlarged. Partial filling defects due to acute PE are often centrally located, however, when eccentrically located they form acute angles with the vessel wall. Chronic PE can manifest as complete occlusive disease in vessels that are smaller than adjacent patent vessels. The radiologist will need to determine the quality of a CT pulmonary angiographic study and whether PE is present. If the quality is poor, the radiologist should then identify which pulmonary arteries have been rendered indeterminate and whether additional imaging is necessary.
Wittram, Conrad. CT angiography of pulmonary embolism: diagnostic criteria and causes of misdiagnosis. Radiographics 2004 vol:24 iss:5 pg:1219 -1238
PE is the third most common acute cardiovascular disease after MI and stroke. It results in thousands of deaths each year due to the fact it often goes undetected. Diagnostic tests for thromboembolic disease include D-dimer, which has a high sensitivity but poor specificity in this setting, ventilation-perfusion scintigraphy, which has a high sensitivity but very poor specificity, and lower limb ultrasonography, which has a high specificity but low sensitivity. CT pulmonary angiography has been evaluated with meta-analysis and has demonstrated sensitivities of 53%–100% and specificities of 83%–100%. These are wide ranges which are explained in part by improving technology. Pulmonary angiography, the diagnostic standard of reference for confirming or refuting a diagnosis of pulmonary embolism, remains underused.
Refer to section on diagnostic criteria beginning on page 1221