CT Pulmonary Angiography > Pulmonary Embolus > Significance

Significance of Pulmonary Embolus

The incidence of pulmonary embolism (PE) is unknown, however it is estimated that approximately 600,000 cases of PE occur annually in the United States. Of these, approximately 250,000 patients are hospitalized. The mortality rate for pulmonary embolism is known to be high and in the Prospective Investigation of Pulmonary Embolism Diagnosis I (PIOPED I) study the fatality during one year follow up in patients diagnosed with pulmonary embolism was 10%. A Medicare study including patients 65 years of age or older reported 30 day case fatality rates in patients with PE of 13.7%.

It has been shown that if the diagnosis of PE is made promptly and appropriate therapy initiated immediately, the mortality rate can be reduced. The key for the correct diagnosis of PE is a high index of clinical suspicion. However, the clinical manifestations of pulmonary embolism are many fold and clinical assessment has been shown to be both nonspecific and not very sensitive. There are a multitude of laboratory tests such as arterial blood gases, electrocardiography, and chest radiography which can be helpful in excluding other diseases mimicking PE, but they typically do not allow the reliable diagnosis of PE.

The advent of the D-dimer blood test has shown promising results and the test has good sensitivity and specificity in patients who present without other systemic illnesses. However, imaging remains the mainstay in the diagnosis of PE. Several imaging tests are currently available in order to assess the pulmonary vasculature for presence of PE. These include ultrasonography, nuclear medicine (ventilation/perfusion scanning), pulmonary angiography, computed tomography and magnetic resonance angiography. In this section of the tutorial we review the current knowledge on the imaging diagnosis of acute PE with special emphasis on the noninvasive techniques.