Pulmonary Embolism on CT Imaging: Key Signs and Clinical Implications

When evaluating patients suspected of pulmonary embolism (PE), computed tomography (CT) plays a pivotal role in accurate diagnosis. One of the hallmark findings on standard chest CT is the presence of wedge-shaped areas of increased density within the lung parenchyma. These opacities typically point toward the pleura and are often indicative of pulmonary infarction—a complication that arises when blood flow to a portion of the lung is severely reduced or completely blocked due to an embolus.

Common CT Findings in Pulmonary Embolism

The wedge-shaped consolidations observed on imaging are not only radiological clues but also reflect underlying tissue damage. These high-density regions result from hemorrhagic necrosis in the affected lung segments, primarily caused by occlusion of distal pulmonary arteries. In addition to these characteristic patterns, some patients may exhibit signs of poor lung aeration or volume loss in the involved areas, further suggesting compromised perfusion and ventilation.

Detecting Clots with CT Angiography (CTA)

For a more definitive assessment, pulmonary CT angiography (CTA) is considered the gold standard. This specialized imaging technique allows clinicians to visualize the pulmonary vasculature in detail. A critical finding on CTA is the presence of filling defects—areas of low attenuation—within the main pulmonary artery or its segmental and subsegmental branches. These filling defects represent thromboemboli, most commonly originating from deep vein thrombosis (DVT) in the lower extremities.

The migration of a clot from the leg veins to the lungs can lead to partial or complete obstruction of blood flow through the pulmonary circulation. When a large vessel is blocked, the right side of the heart must work harder to pump blood against increased resistance. Over time, this strain can result in right ventricular dilation and hypertrophy, a condition known as acute cor pulmonale.

Implications of Right Heart Strain

Enlargement of the right atrium and right ventricle is a significant prognostic indicator in patients with massive or submassive PE. It suggests hemodynamic instability and is associated with higher mortality rates. Radiologists often assess the ratio of the right ventricle to the left ventricle (RV/LV ratio) on axial CT images; a ratio greater than 0.9 is generally considered abnormal and may prompt more aggressive treatment strategies.

In summary, CT imaging provides essential insights into both the direct and indirect signs of pulmonary embolism. From peripheral wedge-shaped infiltrates to central vascular occlusions and secondary cardiac changes, these findings help guide timely diagnosis and management. Early recognition of these imaging features enables healthcare providers to initiate life-saving interventions, such as anticoagulation therapy or thrombolysis, improving patient outcomes significantly.