Cardiac enlargement in a normal infant.

Abstract

The most obvious finding in this patient is the clear Space between the anterior pericardium and the chest wall. This clear space is frequently seen in infants and small children and represents the thymus lying anterior to the heart . Since the thymus separates the anterior pericardium from the chest Wall, a clear appreciation of the thickness of the right ventricular anterior wall is obtained . In systole a normal small separation is seen anteriorly and posteriorly between the visceral and parietal layers of the pericardium . On the 2-dimensional echocardiogram (Fig . 2), the homogeneous echoes arising from the thymus can be seen anterior to the right ventricular outflow tract in the parasternal long and short axis views . In the suprasternal notch long axis view, the thymus can be seen anterosuperior to the ascending aorta . The differential diagnosis of an anterior clear space on the M-mode echocardiogram includes the thymus, pericardial effusion, and mediastinal mass . The 2-dimensional echocardiogram is helpful in fferentiating these conditions . On the 2-dimenSional echocardiogram, the thymus has the reflectance properties of tissue rather than fluid . Mediastinal tumors frequently exhibit nonuniform echo reflectance because of cystic areas present within Pediatric Cardiology