Radiological Assessment of Left Atrial Size in Infants

IN ADULT cardioroentgenology, evaluation of selective enlargement of the left atrium rests upon many findings. These include visualization of a double density along the right cardiac border, localized prominence in the “cardiac waist” on the left just below the prominence normally occupied by the main pulmonary artery segment (2), obliteration of the aortic pulmonic window, eleva tion of the left main-stem bronchus, and the selective displacement of the esophagus on the cardioesophagram. Application of the adult criteria of left atrial enlargement in the examination of children under two and a half years of age presents serious difficulties familiar to most pediatricians and pediatric radiologists (4). This is not well clarified in the literature except for passing mention of “false left atrial enlargement” (3). In infants (children under two and a half years of age will be referred to as infants in this report), the double density on the right cardiac border is frequently seen in the normal. An enlarged left atrium is more likely to compress the left main-stem bronchus than elevate it. Therefore, cardioesophagography remains the only accurate method of detecting left atrial enlargement in this age group (short of angiocardiography) and requires critical evaluation. Our purpose is to emphasize the criteria for left atrial enlargement in these infants. Materials and Methods One hundred and twenty esophagographic studies, performed in infants for extracardiac reasons, were reviewed. The supine position was used in all cases. Thirty-six of the 120 examinations were selected for analysis because multiple “spots” of the well filled esophagus had been recorded in each instance. In 19 of the 36, segmental indentation on the esophagus suggesting left atrial enlargement was noted on more than one of the spot-films. In 4 a single spot-film recorded localized indentation, and in 13 no localized indentation was noted on the spot-films. Subsequently, 25 children with no heart disease were subjected to cine-esophagography. Analysis of the frames in each study revealed segmental esophageal indentation, varying from 3 to 25 per cent of the frames. In addition, cine-esophagrams were obtained in 25 children with varying congenital heart lesions. In these, independent evaluation of the left atrial size was made from angiocardiography, electrocardiography, and the physiologic data recorded during cardiac catheterization. Discussion The infant's chest is proportionately shorter and wider than the adult's (5), and in infants the general size and configuration of the heart change from inspiration to expiration considerably more than in adults. Segmental esophageal indentation by a normal left atrium occurs when expiration and atrial diastole coincide. The size of the indentation or the esophageal curve varies during the expiratory event.