Epidemiology of Congenital Heart Disease
David E. Fixler
Congenital heart disease (CHD) is a leading cause of death during the first year of life. Malformations of the heart occur in about 8:1,000 liveborn infants, resulting in up to 36,000 cases/year in the United States. Children with CHD use between 25% and 30% of the beds in most pediatric intensive care units and therefore consume a large fraction of pediatric health care resources. Because most severe cases now are being managed successfully by surgery, most of these patients are surviving into their reproductive years. Recent studies have shown that the children of women with CHD are at much greater risk of having cardiac malformations. In the next decade, the prevalence of CHD will increase as a result of longer survival and the greater incidence of heart defects in the children of survivors. Pediatric health care providers need to be informed of the prevalence of CHD, the familial risk of CHD recurrence, and risk factors for CHD.
PREVALENCE OF CONGENITAL HEART DISEASE
The prevalence of CHD is the ratio of the number of cases to the number of births in a defined population. Estimating the prevalence accurately requires precise diagnostic criteria for the identification of cases and complete ascertainment of all cases. Diagnostic criteria may include mild cases recognized solely by physical examination, and echocardiography, or it may be restricted to more severe forms diagnosed by cardiac catheterization, surgery, or autopsy. Many types of CHD are not diagnosed until after the neonatal period; therefore, the prevalence rate is affected by the length of the period of observation. In the prospective study by Hoffman and Christianson, data are provided regarding the prevalence of CHD at various age intervals (Table 52.1). These data indicate that fewer than half of the cases were identified during the first week of life.
The reported prevalence of CHD in the United States varies from study to study because of differences in diagnostic criteria, methods of diagnosis, and completeness and length of follow-up (Table 52.2). Important discrepancies among these studies are noted that account for the large differences in reported prevalence rates. The prevalence of CHD among autopsied stillborn infants is 76.9 in 1,000, which is nearly ten times higher than the rate found in liveborn infants. If stillbirths are included in the prevalence figures, the rate increases by about 0.5 in 1,000. The prevalence figure also is influenced by the inclusion of infants born prematurely who have patent ductus arteriosus. Such patients were excluded in most of the recent studies listed in Table 52.2. Which prevalence figure is most correct depends on how the data are to be used. For example, in estimating regional costs of inpatient services, use of the prevalence rates for severe CHD would be most appropriate. In examining the association of heart disease with specific environmental exposures during pregnancy, however, the inclusion of mild cases would be more appropriate.
Prevalence of Specific Types
The frequency of occurrence of various types of CHD among liveborn infants is shown in Table 52.3. This determination is based on 4,390 cases diagnosed in the first year of life from 1981 to 1989 by the Baltimore-Washington Infant Study. These cases included liveborn infants whose condition was diagnosed by echocardiography, cardiac catheterization, surgery, or autopsy. Diagnoses of patent ductus arteriosus in premature infants and mitral valve prolapse were excluded. Isolated ventricular septal defects are by far the most common type of CHD noted, accounting for nearly one-third of all congenital heart defects. Other lesions diagnosed frequently include pulmonic stenosis, atrial septal defect, atrial ventricular septal defect, tetralogy of Fallot, D-transposition of the great arteries, coarctation of the aorta, and hypoplastic left heart syndrome. These eight lesions account for approximately 75% of all cases of CHD. Several other lesions such as cardiomyopathy, pulmonary atresia with intact septum, total anomalous pulmonary venous connection, truncus arteriosus, tricuspid atresia, and interrupted aortic arch are less common but are frequently encountered in critically ill infants in pediatric intensive care units. Therefore, one’s impression is biased by the setting of clinical practice.
CLUSTERING OF CONGENITAL HEART DISEASE WITH OTHER CONGENITAL ANOMALIES
Noncardiac congenital anomalies are frequently seen in infants with CHD. Data from the Baltimore-Washington Infant Study indicate that 27.7% of patients with CHD had associated noncardiac defects. This clustering of birth defects is useful for early
diagnosis of CHD, because the presence of certain anomalies may be the initial indication that a thorough cardiac evaluation is needed. For example, because 50% of infants with Down syndrome have CHD, all infants with trisomy 21 should have complete cardiac evaluations in the first month of life. Other conditions that have a substantial risk of underlying CHD are listed in Table 52.4.
diagnosis of CHD, because the presence of certain anomalies may be the initial indication that a thorough cardiac evaluation is needed. For example, because 50% of infants with Down syndrome have CHD, all infants with trisomy 21 should have complete cardiac evaluations in the first month of life. Other conditions that have a substantial risk of underlying CHD are listed in Table 52.4.
TABLE 52.1. CUMULATIVE PREVALENCE OF CONGENITAL HEART DISEASE PER 1,000 LIVEBORN CHILDREN | ||||||||||||||||||
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TABLE 52.2. MAJOR US SURVEYS OF CONGENITAL HEART DISEASE | |||||||||||||||||||||||||||||||||||||||||||
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