Congenital heart disease (con, together; genitus, born) is often viewed as a group of gross structural abnormalities that are present at birth. Although not incorrect, this definition requires elaboration and qualification. Prenatal diagnoses have been possible for more than 25 years.2 At about embryonic day 20 in the human fetus, progenitor cells within the mesoderm become committed to a cardiogenic destination.3 Most malformations compatible with 6 months of intrauterine life permit live offspring at term. A given malformation may exist in relative harmony with the fetal circulation, only to be modified considerably, at least physiologically, by dramatic circulatory changes at birth.4 Weeks, months, or years may then elapse before an anomaly reveals itself as characteristic or typical. A functionally normal aortic valve that is congenitally bicuspid at birth may take decades to fibrose, calcify, and present as overt aortic stenosis. Conversely, a malformation may disappear, as is the case with spontaneous closure of a ventricular septal defect. Congenital malformations of the heart and circulation are not fixed anatomic defects that appear at birth but instead are anomalies in flux that originate in the early embryo, evolve during gestation, survive the dramatic circulatory alterations at birth, and change considerably during the course of extrauterine life.
Congenital heart disease was once the exclusive and legitimate domain of pediatrics, but survival patterns have changed appreciably. 5,6 In the United States today, there are more adults with congenital heart disease than there are infants and children; these new generations of patients are best cared for by specially trained cardiologists.7 Clinical presentations, especially in adults,8,9 can be exceptionally complex.10–12 Furthermore, certain defects that are actually or potentially of functional significance are not gross structurally, such as congenital complete heart block, either isolated (see Chapter 4) or with congenitally corrected transposition of the great arteries (see Chapter 6) or left isomerism (see Chapter 3); Wolff-Parkinson-White preexcitation, either isolated or complicated (see Chapter 13); absence of a sinus node, as with a superior vena caval sinus venosus atrial septal defect (see Chapter 15) or left isomerism (see Chapter 3); ventricular tachycardia with the long QT syndromes13; or arrhythmogenic right ventricular dysplasia. Still other abnormalities, such as Marfan syndrome, which is the result of mutations in the gene that encodes fibrillin-1, are actually or potentially of functional significance but are not necessarily manifest at birth as gross structural malformations and, as a matter of convention, are usually not classified as congenital.14 And a handful of odd defects tend to escape inclusion, such as congenital kinking of the internal carotid artery