Echocardiography is useful for the detection and management of pericardial effusions, cysts, tamponade, and congenitally absent pericardium . Therapeutic maneuvers such as pericardial windows, drains, and pericardiocentesis are more frequently being performed under echocardiographic guidance. Transesophageal echocardiography is useful for the diagnosis of perioperative tamponade and previously unrecognized pericardial effusions as well as the differentiating between restrictive cardiomyopathy and constrictive pericarditis.
The pericardial sac normally contains 5-30 ml of fluid which serves as lubricant. It is difficult to visualize on TEE examination. Larger effusions can separate myocardium from pericardium creating echo free spaces. Echocardiography is very effective in quantifying the amount of pericardial effusion and assessing diastolic dysfunction associated with tamponade.
Fluid in the pericardium appears as echo lucent space and is best appreciated in the mid esophageal four chamber view and the transgastric mid short gastric view.
The pericardium is a thin layer that is difficult to visualize. The pericardium may become thickened and/or calcified from inflammation. Pericarditis may result in a pericardium that begins to restrict myocardial filling resulting in constrictive pericarditis.
Anatomy
The pericardium comprises of two layers, the parietal and the visceral layer. The visceral layer attaches to the epicardial layer of the heart and great vessels. The parietal layer forms a cavity that is bounded by the pleural surfaces laterally, attaches to the diaphragm inferiorly, and is attached superiorly and posteriorly. Superiorly, the pericardium is attached to the great vessels just distal to their origin. Posteriorly, the pericardium is attached to the vena cava at the atrial level. Areas where the visceral and parietal pericardium join are called pericardial reflections. These pericardial reflections result in the formation of oblique sinus posteriorly and transverse sinus superiorly. The pericardial cavity is a potential space between the two layers and usually contains a small amount of pericardial fluid which lubricates the two layers. The pericardial fluid is an ultrafiltrate of the plasma.
Anatomy of Pericardium
Function
The exact function of the pericardium is unknown. The pericardium serves as a separating border from surrounding mediastinal structures.Even though the function of the pericardium remains to be defined, normal pericardium prevents excessive dilation of the chambers, limits ventricular filling (right ventricle being more sensitive to this force than the left ventricle) and may prevent excessive atrioventricular valve incompetence. The pericardium provides restraint for the heart to resist dilation if atrioventricular valves are incompetent.
Embryology
The mesocardium, a double fold of coelomic epithelium, suspends the heart in the pericardial cavity. During the formation of the heart, the mesocardium breaks down, leaving the transverse sinus of the pericardium behind. The pericardium is attached to the venous (caudal) and arterial (cranial) ends of the heart tube and remains attached in the adult. The transverse sinus lies dorsal to the heart tube and connects the left and right sides of the pericardial cavity.
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Lateral View
Coronal View
Transverse Sinus Views
The best view for the transverse sinus is the midesophageal aortic valve long axis view. The transverse sinus forms a small triangular echo space between the left atrium, aorta, and pulmonary artery. The transverse sinus can be confused with a cyst or an abscess cavity. Fluid is rarely seen in the transverse sinus.
Air in the Transverse Sinus
Air in the Transverse Sinus
Oblique Sinus Views
Oblique Sinus is a pericardial reflection inferior to the transverse sinus between the right and left pulmonary veins and medial to inferior vena cava. The oblique sinus is usually difficult to visualize because fluid in the oblique sinus occurs or accumulates less often than other areas of the pericardium. The oblique sinus is surrounded by attachments of the pulmonary veins to the left atrium which usually keeps the spaced closed.
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