Incidence in Childhood.

The true incidence of congenital cardiovascular malformations is difficult to determine accurately, partly because of difficulties in definition. The incidence in fetal life exceeds that in early childhood because very complex lesions are associated with early nonviability or later in utero death. Consequently, approximately 0.8% of live births are complicated by a cardiovascular malformation. This figure does not take into account what may be the two most common cardiac anomalies: a congenital, functionally normal bicuspid aortic valve and prolapse of the mitral valve.

Specific defects can have a definite sex preponderance: PDA, Ebstein anomaly of the tricuspid valve, and secundum atrial septal defect (ASD) are more common in females, whereas aortic valve stenosis, coarctation of the aorta, hypoplastic left heart syndrome, pulmonary and tricuspid atresia, and transposition of the great arteries (TGA) are more common in males.

Extracardiac anomalies occur in approximately 25% of infants with significant cardiac disease, and their presence may significantly increase mortality. The extracardiac anomalies are often multiple. One third of infants with both cardiac and extracardiac anomalies have some established syndrome.

The Adult Patient.

Thanks to the great successes in pediatric cardiac care, the overall number of adult patients with congenital heart disease (CHD) is now greater than the number of pediatric cases. Indeed, more than 90% of patients born in 1990 in Belgium survived to at least 18 years of age.⁶ In the United States, 40,000 babies are born each year with congenital heart defects. More than 35,000 of them will reach 18 years of age and beyond. At present, approximately 1.3 million American adults have congenital heart defects, more than 50% of which are classified as complex and in need of life-long expert surveillance. These moderately to very complex patients are at significant risk for premature mortality, reoperation, or future complications of their conditions and their treatments. Many patients, especially those with moderately to very complex conditions, should see a specialist trained in the care of adult CHD. Currently, not enough such practitioners or facilities are available to always make this possible. Adult patients should have been taught in adolescence about their condition, their future outlook, and the possibility of further surgery and complications if appropriate, and they also should have been advised about their responsibilities in ensuring self-care and professional surveillance. Copies of operative reports should accompany patients being transferred for adult care, along with other key documents from the pediatric file.

Table 62-1 lists the types of patients who should be considered “simple” and suitable for community care. Tables 62-2 and 62-3 show the diagnoses for “moderately complex” and “very complex” patients. Moderately and very complex patients should be monitored throughout their lives in a specialized center.

CHD in an adult is not simply a continuation of the childhood experience. The patterns of many lesions change in adult life. Arrhythmias are more frequent and of a different character (see Chapter 37). Cardiac chambers often enlarge, and systolic dysfunction tends to develop in the ventricles. Bioprosthetic valves, prone to early failure in childhood, last longer when implanted at an older age. The comorbid conditions that tend to develop in adult life often become important factors needing attention. As a result, the needs of these adult patients with CHD are often best met by a physician or team familiar with both pediatric and adult cardiology issues. For the best results, congenital heart surgery and interventional catheterization procedures should be performed at centers with adequate surgical and institutional volumes of congenital heart cases at any age. Patients undergoing surgery in a nonspecialist environment, even when operated on by a congenital heart surgeon, suffer threefold increased mortality in comparison to those in specialized congenital heart centers.⁷ In most cases the specialist environment is a children’s hospital, probably a nonsustainable model for optimal care as this population expands.

Echocardiographic studies, diagnostic heart catheterizations, electrophysiologic studies, magnetic resonance imaging (MRI), and other imaging of complex cases (see Chapters 14 to 19) are best done where qualified staff has relevant training, experience, and equipment. Ideally, patient care should be multidisciplinary. Special cardiology and echocardiography skills are essential, but individuals with other special training, experience, and interest should also be accessible, including congenital heart surgeons and their teams, nurses, reproductive health staff, mental health professionals, medical imaging specialists, respiratory consultants, and others.

Genetic.

A single gene mutation can be causative in the familial forms of ASD with prolonged atrioventricular (AV) conduction; mitral valve prolapse; VSD; congenital heart block; situs inversus; pulmonary hypertension; and the Noonan, LEOPARD, Ellis–van Creveld, and Kartagener syndromes (see Syndromes in Congenital Heart Disease later). The genes responsible for several defects have now been identified (e.g., long-QT syndrome, Holt-Oram syndrome, Marfan syndrome, hypertrophic cardiomyopathy, supravalvular aortic stenosis), and contiguous gene defects on the long arm of chromosome 22 underlie the conotruncal malformations of DiGeorge and velocardiofacial syndromes. However, at present, less than 15% of all cardiac malformations can be accounted for by chromosomal aberrations or genetic mutations or transmission (see Chapters 32 and 33).

It is interesting, but unexplained, that several different gene defects may lead to the same cardiac malformation (e.g., AV septal defect). Furthermore, the finding that with some exceptions, only one of a pair of monozygotic twins is affected by CHD indicates that most cardiovascular malformations are not inherited in a simple manner. However, this observation may in the past have led to an underestimation of the genetic contribution because most recent twin studies reveal more than double the incidence of heart defects in monozygotic twins but usually in only one of the pair. Family studies indicate a 2- to 10-fold increase in the incidence of CHD in siblings of affected patients or in the offspring of an affected parent. Malformations are often concordant or partially concordant within families. Routine fetal cardiac screening of subsequent pregnancies should be performed in such circumstances.

Environmental.

Maternal diabetes, rubella, ingestion of thalidomide and isotretinoin early during gestation, and chronic alcohol abuse are environmental insults known to interfere with normal cardiogenesis in humans. For example, the incidence of tetralogy of Fallot with pulmonary atresia is increased 10-fold in the offspring of diabetic mothers. Rubella syndrome consists of cataracts; deafness; microcephaly; and either singly or in combination, PDA, pulmonary valve and/or arterial stenosis, and ASD. Thalidomide exposure is associated with major limb deformities and, occasionally, cardiac malformations without a predilection for a specific lesion. Tricuspid valve anomalies are associated with the ingestion of lithium during pregnancy. Fetal alcohol syndrome consists of microcephaly, micrognathia, microphthalmos, prenatal growth retardation, developmental delay, and cardiac defects (often defects of the ventricular septum) in approximately 45% of affected infants.