Chest radiography is rarely diagnostic of specific cardiac lesions, but it is a relatively quick and relatively inexpensive method to identify lung disease and screen for suspected cardiac anomaly in symptomatic infants. Chest radiographs often appear normal or near normal in the first day or days of life with many cardiac anomalies, and may not be cost effective in asymptomatic infants with an isolated murmur (i.e., no cyanosis (See Color Plate) or congestive signs or symptoms). However, in cyanotic or symptomatic infants, the presence or absence of cardiomegaly, increased pulmonary arterial or venous markings, diminished pulmonary arterial markings, or right aortic arch provides important information regarding the presence of a cardiac anomaly (see Fig. 33-9 and 33-10). In combination with physical exam and electrocardiographic findings, chest radiographic findings may provide important information concerning the possible presence of specific cardiac anomalies that may aid in early management before an echocardiogram can be obtained. The heart size should be differentiated from the thymic shadow. Cardiomegaly is indicated by a cardiothoracic ratio greater then 0.6 in an anterior-posterior projection in the presence of an adequate inspiration. The aortic arch position can be assessed, even in the presence of a large overlying thymus, by deviation of the trachea to the opposite side. Associated noncardiac anomalies that provide clues to the cardiac diagnosis may be discovered by radiographic findings, for example, heterotaxy (asplenia syndrome, malrotation), absence of the thymus gland (DiGeorge syndrome), vertebral anomalies (VACTERL association), and abnormal sternal ossification (Down syndrome).

Electrocardiography can be useful in evaluation for cardiac anomaly and arrhythmogenic disorders and in particular for diagnosis and management of arrhythmia (see Arrhythmias). Electrocardiographic interpretation in neonates has several caveats. However, when placed within the context of other physical exam and radiographic findings, electrocardiographic findings can provide a timely advantage in diagnosis and management of suspected cardiac anomaly (see Fig. 33-9 and 33-10). Electrocardiography is also useful for timely recognition of life-threatening arrhythmogenic disorders, particularly within the context of other findings; for example family history and borderline prolonged QT interval (QTc).