SVCAoPARARVLVLAABFigure 139-3 A, Parts of the heart whose outlines can be identified on a routine chest x-ray. B, Routine posteroanterior x-ray of the normal cardiac silhouette. Ao, Aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle; SVC, superior vena cava. (From Andreoli TE, Carpenter CCJ, Plum F, et al, editors: Cecil Essentials of Medicine, ed 2, Philadelphia, 1990, WB Saunders.) less than 55% in infants under 1 year of age and less than 50% in older children and adolescents. An enlarged heart may be due to an increased volume load (left-right shunt) or due to myocardial dysfunction (dilated cardiomyopathy). The shape of the heart may suggest specific congenital heart defects. The most common examples are the boot-shaped heart seen with tetralogy of Fallot, the egg-on-a-string seen with dextroposed transposition of the great arteries, and the “snowman” seen with supracardiac total anomalous pulmonary venous return. The chest x-ray can aid in the assessment of pulmonary blood flow. Defects associated with left-to-right shunting have increased pulmonary blood flow (shunt vascularity) on x-ray. Right-to-left shunts have decreased pulmonary blood flow.
Echocardiography has become the most important noninvasive tool in the diagnosis and management of cardiac disease,providing a full anatomic evaluation in most congenital heartdefects (Fig. 139-4). Physiologic data on the direction of bloodflow can be obtained with the use of pulsed, continuous wave,and color flow Doppler. Imaging from multiple views providesan assessment of spatial relationships. Three-dimensional (3D)and four-dimensional (4D) imaging now allows reconstruction of the heart and manipulation of the images to providemore detail, especially with regard to valve structure and function. Prenatal or fetal echocardiography can diagnose congenital heart disease by 18 weeks of gestation and allows for delivery of the infant at a tertiary care hospital, improving thetimeliness of therapy. Many congenital heart defects now aresurgically repaired based on the echocardiogram without needfor cardiac catheterization.
Figure 139-4 Four-chamber echocardiogram of an atrial septal defect. The defect margins are identified by the two arrows. LA, Left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.
Transesophageal echocardiography (TEE) provides better imaging when transthoracic imaging is inadequate. It is used intraoperatively to assess results and cardiac function after surgery. TEE and intracardiac echocardiography are used to guide interventional catheterization and radiofrequency ablation of dysrhythmias.