Chest x-ray is a first-level imaging modality in patients with a suspected pericarditis or pericardial effusion in order to detect the presence of a cardiomegaly (may suggest a pericardial effusion), pericardial calcifications (chronic and constrictive pericarditis) and/or concomitant pleuropulmonary disease as first screening (e.g. pleural effusion, pneumonia, tuberculosis, lung cancer and hilar and mediastinal enlargement) (Fig. 4.1).

In a patient with pericarditis and without significant structural heart diseases, the chest x-ray may be absolutely normal (Fig. 4.2). A pericardial effusion is able to increase the size of the cardiac silhouette only if >300 mL, and cardiac silhouette may assume a “bottle” shape in the presence of large pericardial effusions, especially when chronic and slowly accumulating (Fig. 4.3) [2].

Transthoracic echocardiography is the first-line imaging test in patients with suspected pericardial disease (Class I indication, LOE C) [2]. One of the first applications of echocardiography was the detection of pericardial effusion. Even nowadays, echocardiography offers the simplest and cheapest diagnostic option to detect the presence of pericardial effusion, providing a semiquantitative assessment of the size, that can be easily performed even at bedside and in urgent/emergency settings.

In clinical practice, the size of pericardial effusion on M-mode, 2D echocardiography is qualitatively assessed by the end-diastolic distance of the echo-free space between the epicardium and parietal pericardium: small (<10 mm), moderate (10–20 mm) and large (>20 mm) (Fig. 4.4) [2]. Pericardial fluid accumulates following available spaces and gravity forces. On the left lateral decubitus, the fluid starts accumulating posteriorly (mild effusions), and then after the complete filling of the posterior space, pericardial effusion becomes circumferential. On this basis, an isolated anterior pericardial echo-free space should be considered as evidence of increased epicardial fat instead of pericardial fluid, especially in the absence of previous cardiac surgery, trauma or pericarditis with or without interventional procedures. CT and CMR may provide better tissue characterization of the echo-free space (Fig. 4.5).

Additional contributes of echocardiography include follow-up studies for pericardial effusions, assessment of cardiac tamponade, constrictive features, evaluation of left and right ventricular function and kinesis, as well as concomitant structural heart diseases. A detailed discussion on echocardiographic features of cardiac tamponade and constrictive pericarditis will be reviewed in the specific chapter on these pericardial syndromes. On echocardiography, a concomitant pleural effusion can be detected. Left pleural effusion can be differentiated from pericardial effusion since pleural effusion is posterior to the thoracic descending aorta (Fig. 4.6).

The normal pericardium is visible as a thin curvilinear structure surrounded by the hypodense mediastinal and epicardial fat and has a thickness ranging between 0.7 and 2.0 mm. The pericardial sinuses and their respective recesses are well visible on computed tomography (CT).

CT is a second-level complementary imaging modality that is especially useful for the study of pericardial calcifications as well as concomitant pleuropulmonary diseases. In addition, CT may be helpful to provide some tissue characterization of pericardial fluid. Attenuation values of pericardial fluid (HU) yield information with regard to nature of fluid: low attenuation values (e.g. 0–20 HU) indicate a simple effusion and a transudate, intermediate values (e.g. 20–60 HU) are suggestive of a proteinaceous, exudative effusions, while high attenuation values (>60 HU) suggest haemorrhage [7–10].

CT is the most accurate technique to image calcified tissue, and it is especially helpful to depict the extension of calcifications allowing a better surgical plan for pericardiectomy. Nowadays modern multi-detector CT scanners combine both acquisition speed and high contrast and spatial resolution providing excellent anatomical details. Low-radiation cardiac CT is feasible using prospective electrocardiographic triggering. In clinical practice, CT provides limited contribution to the functional study of the heart and pericardium [2, 10]. Intravenous administration of iodinated contrast material is able to detect pericardial inflammation since the inflamed pericardium is enhanced after contrast injection.

Additional contribution of CT studies includes the evaluation and diagnosis of pericardial masses and cysts and the congenital partial or complete absence of the pericardium.

Cardiac magnetic resonance (CMR) is another second-level imaging technique for the study of pericardial and myopericardial diseases [2].

Similar to CT, the normal pericardium appears as a thin hypointense (“dark”) curvilinear structure surrounded by hyperintense (“bright”) mediastinal and epicardial fat on T1-weighted imaging. Normal pericardial thickness is less than 2 mm (Fig. 4.7).