What is the term for the thin radiopaque line/area surrounding the heart in chest X-rays (X-ray) of pericardial effusion?

From the Guidelines

The thin radiopaque line surrounding the heart in chest X-rays of pericardial effusion is called the "epicardial fat pad sign" or "epicardial fat stripe." This radiographic finding appears as a thin, white line that represents the interface between the pericardial fluid and the epicardial fat. In normal chest X-rays, the epicardial fat is not distinctly visible as a separate line. However, when fluid accumulates in the pericardial space during pericardial effusion, it creates a space between the heart and the pericardium, allowing the epicardial fat to become visible as a distinct radiopaque line. This sign is important diagnostically because it helps radiologists and clinicians identify the presence of pericardial effusion. The visibility of this line occurs because X-rays are attenuated differently by fluid, fat, and cardiac tissue, creating contrast between these structures. While the epicardial fat pad sign is helpful, it's worth noting that echocardiography remains the gold standard for confirming and quantifying pericardial effusion, as stated in the 2015 ESC guidelines for the diagnosis and management of pericardial diseases 1. Some key points to consider when evaluating pericardial effusion include:

• The size of the effusion, which can be qualitatively assessed by the end-diastolic distance of the echo-free space between the epicardium and parietal pericardium 1
• The hemodynamic impact of the effusion, which can be assessed using echocardiography and Doppler studies 1
• The potential causes of the effusion, which can include idiopathic, infectious, and malignant etiologies 1
• The importance of monitoring for complications, such as cardiac tamponade and effusive-constrictive pericarditis 1
• The role of pericardiocentesis in the diagnosis and management of pericardial effusion, including the use of fluoroscopic and echocardiographic guidance 1

From the Research

Pericardial Effusion on Chest X-Rays

The thin radiopaque line or area surrounding the heart in chest X-rays of pericardial effusion is related to the pericardial sac and its contents.

• The pericardial sac is a fibroserous sac that surrounds the heart and contains a small amount of fluid, which can increase in cases of pericardial effusion 2, 3.
• Pericardial effusion is the accumulation of excess fluid in the pericardial space, which can be caused by various conditions such as inflammation, infection, or trauma 4, 5.
• The diagnosis of pericardial effusion can be made using various imaging modalities, including chest X-ray, echocardiography, and computed tomography scan 6.

Radiographic Findings

The radiographic findings of pericardial effusion on chest X-ray include:

• An enlarged cardiac silhouette, which can be caused by the accumulation of fluid in the pericardial space 2, 3.
• A thin radiopaque line or area surrounding the heart, which represents the pericardial sac and its contents 4, 5.
• The size and shape of the pericardial effusion can vary, and it can be located in different parts of the pericardial space 6.

Clinical Significance

The clinical significance of pericardial effusion depends on the underlying cause and the amount of fluid accumulated in the pericardial space.

• Small effusions may be asymptomatic, while large effusions can cause cardiac tamponade, which is a life-threatening condition 2, 3.
• The treatment of pericardial effusion depends on the underlying cause and the severity of the condition, and can include pericardiocentesis, pericardial window, and sclerosing therapies 4, 5, 6.