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The incidence of congenital heart disease in the United States is approximately 8 per 1000 live births.1,2 Many infants who are born alive with cardiac defects have anomalies that do not represent a threat to life, at least during infancy. Almost one-third of those infants, or 2.6 per 1000 live births, however, have critical disease, which is defined as a malformation severe enough to result in cardiac catheterization, cardiac surgery, or death within the first year of life.3 Today, with early detection and proper management, the majority of infants with critical disease can be expected to survive the first year of life. Most who now survive infancy will join the increasingly large cohort of adults with congenital heart disease.

Estimates of the incidence of specific lesions vary, depending on whether the data are drawn from infants or older children and whether the diagnosis is based on clinical, echocardiography, catheterization, surgical, or postmortem studies.1-4 The incidence in other countries is remarkably similar to that reported for the United States.5,6 Despite these differences in case material, except for bicuspid aortic valve and mitral valve prolapse, it is apparent that ventricular septal defect (VSD) is the most common malformation, occurring in 28% of all patients with congenital heart disease (Table 83–1).

Table 83–1. Incidence of Specific Congenital Heart Defects

Among 2251 infants with critical congenital heart disease in the New England Regional Infant Cardiac Program,3 53.7% were male. Certain defects, however, are more much common in one sex than in the other. Aortic stenosis occurs more often in boys (4:1), and atrial septal defects (ASDs) occur more frequently in girls (2.5:1).

Although earlier theories concerning the etiology of congenital heart diseases suggested that most defects were multifactorial—that is, the malformations are caused by a combination of a hereditary predisposition (presumably caused by abnormalities in the genetic code) and an environmental trigger7—more recent advances in molecular biology suggest that a much higher percentage are caused by point mutations.8

Some abnormalities are caused by chromosomal aberrations (see Chap. 82). Trisomy 21 (Down syndrome) is highly associated with complete atrioventricular (AV) canal, VSDs, and tetralogy of Fallot, and children with Turner syndrome (XO chromosome) frequently ...

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