On standard posteroanterior chest radiography, cardiomegaly is a common finding in patients with pericardial effusion, especially of 200 mL or more; overall sensitivity is 89%. Evolving cardiomegaly in the absence of pulmonary vascular congestion supports the diagnosis of effusion over cardiomyopathy and associated congestive heart failure. A pathognomonic finding on an erect chest radiograph for massive effusions, often more than 1 L, is the "water bottle" heart. This reflects the dependent distribution of fluid within the pericardial space when upright, tapering up toward the pericardial reflection at the level of the proximal great vessels. Another finding associated with pericardial effusion is the "Oreo cookie" or "fat pad" sign on lateral chest radiography. This describes a vertical radiopaque line sandwiched by two vertical radiolucent stripes located between the sternum and RV border. The opaque line represents pericardial fluid separating epicardial fat from pericardial fat within the pericardial space. In tension pneumopericardium, air surrounding the heart creates a sharply delineated air pericardiogram.

Cardiac computerized tomography can define not just the presence of a pericardial effusion but also cardiac anatomy and pericardial pathology. However, its utility in a patient with unstable hemodynamics is limited and usually not practical. Intravenous contrast enhances pericardial inflammation and hemopericardium including active extravasation. Attenuation values of pericardial fluid can aid in characterizing the type of effusion. Transudates have lower radiodensity than exudates, which in turn are less dense than blood or clots. Other computerized tomography findings consistent with cardiac tamponade include compression of cardiac chambers, distension of the venae cavae, and reflux of contrast into the IVC or azygos vein suggesting impaired right-sided filling.

Two-dimensional and Doppler echocardiography are considered first-line imaging for cardiac tamponade. Advantages include a high sensitivity for detecting pericardial fluid and any related mass effect, the ability to assess cardiac function and filling patterns, portability, and the lack of ionizing radiation. However, the utility of transthoracic echocardiography is limited in postcardiac surgery patients due to sonographic artifact from sternal wires, chest tubes, and surgical dressings.

References

• Bogaert J, Francone M. Pericardial disease: value of CT and MR imaging. Radiology. 2013;267:340-356.
• Kearns MJ, Walley KR. Tamponade: hemodynamic and echocardiographic diagnosis. Chest. 2018;153:1266-1275.
• Restrepo CS, Lemos DF, Lemos JA, et al. Imaging findings in cardiac tamponade with emphasis on CT. Radiographics. 2007;27:1595-1610.