In patients with hemodynamic stability, the diagnosis of pulmonary embolism should follow a sequential diagnostic workup, consisting of clinical probability assessment, D-dimer testing, and, if necessary, multidetector CT or ventilation-perfusion scanning.
Various scoring systems have been developed to estimate the pretest probability of pulmonary embolism. A commonly used one is the Wells prediction rule. The most common ECG abnormalities seen in patients with pulmonary embolism are tachycardia and nonspecific ST-T wave abnormalities. The finding of S1Q3T3 is nonspecific and insensitive, occurring in less than 20% of patients with proven pulmonary embolism.
In hemodynamically stable patients with a low or intermediate clinical probability of pulmonary embolism, normal results on D-dimer testing, as measured by a sensitive enzyme-linked immunosorbent assay, avoid unnecessary further investigation. The use of D-dimer assay is of limited value in patients with a high clinical probability of pulmonary embolism. The specificity of an increased D-dimer level is reduced in patients with cancer, pregnancy, the elderly, and hospitalized patients.
Hemodynamically stable patients with high clinical probability or positive D-dimer test results should undergo multidetector CT. CT pulmonary angiography is now the initial imaging modality of choice in the diagnosis of pulmonary embolism. In cases in which multidetector CT is not available or in patients with renal failure or allergy to contrast dye, ventilation-perfusion scanning is an alternative. A normal ventilation-perfusion scan essentially rules out pulmonary embolism.
If venous ultrasonography of the lower limbs is performed first, lung scanning or multidetector CT scanning can be avoided. Hemodynamically stable patients with suspected pulmonary embolism and ultrasonographically confirmed deep venous thrombosis can be given anticoagulant treatment without further testing. Venous ultrasonography should precede imaging tests in pregnant women with suspected pulmonary embolism and in patients with a contraindication to multidetector CT scanning.
In hemodynamically unstable patients who are hypotensive or in shock, multidetector CT scanning should be performed. If CT scanning is unavailable, echocardiography can be performed to confirm the presence of right ventricular dysfunction. Pulmonary angiography is the historical criterion standard for the diagnosis of pulmonary embolism. However, given the invasive nature and risks of contrast, it has largely been replaced by CT pulmonary angiography. The procedure is currently reserved for the rare cases in which catheter-based treatment is indicated.
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Cite this: Jason Chang, Linda Chun. Chest Pain and Shortness of Breath in a 33-Year-Old Man - Medscape - Jul 20, 2020.