Diagnostic imaging and risk stratification of patients with acute pulmonary embolism.

Pulmonary embolism (PE) is the third most common acute cardiovascular disease after myocardial infarction and stroke. The prompt diagnosis, risk stratification, and treatment of patients with acute PE can reduce mortality. Multidetector row computed tomography pulmonary angiography (CTPA) is the most common study used to make the diagnosis of acute PE. CTPA may additionally identify right heart dysfunction or alternative diagnoses. There is a growing body of evidence that computed tomography signs of right heart failure predict patients at higher risk of mortality. At the same time, CTPA has about a 6-fold greater whole body effective dose than ventilation-perfusion (V/Q) scintigraphy, and a much higher dose to breast tissue in particular. V/Q scintigraphy should be considered for patients with contraindications to iodinated contrast or for patients with normal chest radiographs, especially young women. Compression ultrasonography of the proximal lower extremities, an imaging study without ionizing radiation, should be considered for patients suspected of acute PE with signs of lower extremity deep venous thrombosis or for patients with negative CTPA or V/Q scan with discordant clinical probability. This article reviews factors affecting the selection of the best imaging test for a particular patient suspected of acute PE, performance characteristics of diagnostic imaging tests, and imaging findings that correlate with higher mortality.