Cardiovascular Risk in Special Populations IV: Congenital Heart Defects

Congenital heart defects are found in approximately 1 in 100 to 150 newborns and are associated with racial disparities in types, interventions, and mortality.1 Although mortality from heart defects between 1979 and 1997 in the United States for all ages declined 39% (from 2.5 to 1.5 per 100,000 population)1 and in a similar percentage for infants, mortality was 19% higher in blacks than whites, 68.4 vs 55.5 per 100,000, respectively.1 In regard to infants, mortality has decreased considerably in this 18-year period for such major congenital heart disease as transposition of the great arteries, ventricular septal defect (VSD), atrioventricular septal defect, and aortic coarctation.1 Moreover, although mortality decreased in blacks as well as white infants, black infant mortality rates were consistently higher during this period (Figure 1).1 Trends in infant mortality due to congenital heart defects by race, United States, 1979–1997. From Boneva et al1 with permission from the American Heart Association, Inc. ©2001. Overall, the average age of death increased for the common congenital heart defects during this 18-year period but was higher in blacks. The changes for some common congenital heart conditions can be see in Table I.1 For all common congenital heart defects, between 1979–1983 and 1994–1997, the 50th percentile in mortality for whites increased from 7 months to 12 months, and for blacks only from 3 months to 5 months. For most anomalies, although the median and especially 75th percentile ages increased considerably, black mortality persisted at a younger age than whites for virtually all categories (Table II).1 Categories in which deaths in blacks occurred at least at one half the age as whites or lower included VSD, aortic and pulmonic valve anomalies, and single ventricle. Access to medical care, nutrition, and maternal lifestyles and education may be responsible for neural tube defects.2 Higher rates of neural tube defects were found in Hispanic women in Brooklyn than black or non-Hispanic whites.3 Racial variations in congenital defects appear to vary widely among blacks and whites in a study from Atlanta, Georgia.4 Congenital heart defects were found to be more common in American Indians in British Columbia than in the general population.5 Fetal alcohol syndrome may be associated with congenital heart anomalies and the syndrome is particularly common in Native Americans, occurring in up to 103 of 100,000 live births.6 On the basis of a population-based case control study of congenital cardiovascular malformations in the Washington, DC and widespread surrounding area between 1981–1987, birth weight deficits were found for infants with tetralogy of Fallot, endocardial cushion defect, hypoplastic left heart syndrome, pulmonic stenosis, coarctation of the aorta, and atrial and VSDs.7 A retrospective study of racial frequencies in 3 congenital heart malformations of children born in Baltimore hospitals in the 1960’s demonstrated no significant differences between black and white infants in the presence of transposition of the great vessels, coarctation of the aorta, and aortic atresia with left heart hypoplasia.8 An evaluation of congenital cardiac malformations by race and sex was evaluated in infants born in Louisiana in 1988–1989.9 Variability included a significantly higher prevalence of atrioventricular canal defects per 1000 live births in black women (0.74) compared with white women (0.41) and black men (0.20) and white men (0.12). On the other hand, aortic stenosis and/or aortic coarctation were highest in white men. Single ventricle was higher in whites than blacks. Complete transposition of the great arteries was highest in white men (0.560 compared with black men (0.20) and black women (0.17) and white women (0.12). These differences further demonstrated the variability of certain congenital cardiac defects by race and sex. A study of trends in congenital heart disease in Dallas County, Texas, in births from 1971–1984 found a prevalence rate of congenital heart malformations of 6.6 per 1000.10, 11 The rate for whites, 7.2 per 1000, was significantly higher than for Mexican Americans (5.9 per 1000), or blacks (5.6 per 1000) (Table III).11 No differences were seen in the rates related to surgery, cardiac catheterization, or autopsy. Aortic stenosis, endocardial cushion defects, and VSDs were of higher prevalence in white infants and young children (Table IV).11 The median age at diagnosis was similar among racial groups. In regard to socioeconomic variables and timing of referral to cardiologists, no significant differences were seen for family income or educational level of the parents.11 The first comprehensive estimates of leading congenital malformations among minority groups in the Unites States were reported in 1988.6 In the period from 1981 to 1986, the Birth Defects Monitoring Program of the Centers for Disease Control found that Native Americans had the highest rates of atrial septal defect, valve stenosis and atresia, and fetal alcohol syndrome in regard to cardiac anomalies. Rates for patent ductus arteriosus and pulmonic stenosis were highest for blacks. Patent ductus arteriosus was the major cardiac congenital anomaly among blacks as well as Native Americans and Asians, frequently associated with high rates of prematurity. Down syndrome, commonly associated with VSD, was commonest for Hispanics, possibly related to advanced maternal age. Asians had the highest rates of VSD. The Metropolitan Atlanta Congenital Defects Program registry reported results from an evaluation of 5813 major congenital heart defects between 1968 and 1997.12 The overall prevalence during these years was 6.2 per 1000 live births, similar to other findings. However, the prevalence increased to 9.0 per 1000 live births in the past 2 years of the evaluation. The increase began in 1970 and was especially seen in increased prevalence of VSD, atrial septal defect, tetralogy of Fallot, and atrioventricular septal defect (Figure 2).12 The reasons for this increase are unclear but may relate to increased availability of 2-dimensional echocardiography for diagnosis, especially in the case of less severe defects. Prevalence of heart defects by year, Metropolitan Atlanta, 1968–1997. Prevalence is by 10,000 births and is presented as a 5-year moving average. From Botto et al12 with permission from the American Academy of Pediatrics ©2001. A higher overall occurrence of congenital heart defects was found in blacks compared with whites, primarily due to increased peripheral pulmonic stenosis and atrial septal defects. Temporal trends demonstrated an increase in overall rates of heart defects in both blacks and whites. Peripheral pulmonic stenosis increased more rapidly in blacks and VSDs in whites as did coarctation of the aorta. The Texas Birth Defects Registry provided a report on records of children up to 1 year of age with aortic stenosis, coarctation of the aorta, and hypoplastic left heart syndrome born in 1999–2001.13 These malformations were more common in men (7.7 vs 3.35 per 10,000 live births). Hispanic women had a similar prevalence compared with black and non-Hispanic white women.13 Prevalence rates for Hispanic men were lower than in non-Hispanic white men (5.7), and black men still lower, even lower than the rate in black women (1.9 vs 3.5). A factor associated with increased congenital outflow defects included increased maternal age. Of environmental interest, increased prevalence of coarctation was found in the Texas-Mexican border compared with the rest of the state. In terms of sex, death rates appear higher in boys especially in infancy. Boys are more prone to have serious congenital heart conditions such as transposition of the great arteries, pulmonary and tricuspid atresia, aortic stenosis and coarctation of the aorta, and hypoplastic left heart syndrome. At present, there is little information about the causes of racial disparities in mortality, but some recent studies shed some light on these possible causes. Environmental factors, varied among racial groups, may increase risk for congenital heart abnormalities. These include maternal rubella, phenylketonuria, and diabetes, obesity, or exposure to agents such as ibuprofen, indomethacin, sulfasalazine, trimethoprim-sulfonamide, and anticonvulsants.14 Nontherapeutic drug exposure includes marijuana. In regard to conditions in which racial minority groups may be particularly prone, pregestational diabetes may be associated with transposition of the great vessels, hypoplastic heart syndrome, patent ductus arteriosus, and looping defects in the fetus, to name but a few.14 It has been suggested, based on animal model studies, that abnormal glucose levels in the mother leads to embryotoxic apoptotic cellular changes.15 Maternal obesity has been shown to increase risk of aggregate cardiac defects among black women more than 6-fold (odds ratio, 6.5; 95% confidence interval, 1.2–34.9; P=.025).6 Maternal alcohol consumption during the first trimester of pregnancy was associated with a significantly increased risk of VSDs.17 Marijuana use has also been associated with VSDs. Recent studies have variably found an association between maternal smoking and congenital defects including atrial septal defects, atrioventricular septal defects, and tetralogy of Fallot.18 However, black infants appear to have a lower incidence of many congenital heart defects compared with white infants. In the Baltimore-Washington Infant Study, a population-based case control study of 2087 cases of congenital malformations, an excess of white infants was found with aortic stenosis, atrioventricular septal defects, atrial septal defects, coarctation, patent ductus arteriosus, and tetralogy of Fallot.6, 19 Pulmonic stenosis was more common in black infants. Controlling for socioeconomic status disclosed a white excess for L-transposition of the great arteries. Aortic stenosis was limited to low- and middle-income strata.19 However, in a population-based study, the prevalence of birth defects in infants of black and Hispanic women showed no significant variation compared with infants from non-Hispanic white women.20 A large number of chromosomal disorders have been associated with congenital heart disease.21 A population-based study of the 22q11.2 deletion in Atlanta between 1994–1999 found an increased frequency among Hispanics compared with whites, blacks, and Asians.22 This chromosomal abnormality is associated with increased congenital anomalies, especially right aortic arch and interrupted aortic arch, and tetralogy of Fallot. Mortality risk variations in congenital heart disease surgery among racial groups may be influenced by unequal access to care. This was explored by a population-based cohort study utilizing hospital discharge data from 4 states (California, Massachusetts, New York, and Pennsylvania) in 1996.23 Surgical mortality was lower in whites than non-whites (3.7% vs 5.1%, P=.02). Unadjusted mortality rates varied among Asian, Hispanic, black, and “other” groups (5.3%, 4.9%, 4.1%, and 7.3%, respectively; P=.008). When adjusted for risk factors, Asians and Hispanics still had a higher risk of dying from surgery than non-Hispanic whites, but not blacks. Variations appeared between states. For example, blacks had a higher risk of dying vs whites in Massachusetts but a lower risk in Pennsylvania.24, 25 In a study of California hospital discharges after surgical repair for congenital heart disease in patients younger than 18 in 1995–1996, patients with private insurance were younger than those with managed care insurance plans.24 Asians tended to be older than other racial groups but only significantly for VSDs. Native Americans were excluded from this as well as other studies mentioned because of small sample sizes. Considerations of racial disparities in outcomes may relate to recommendations for surgery related to insurance coverage. For example, pediatric heart surgery in patients with managed care insurance appeared to be less likely accomplished in lower mortality hospitals than in children who were covered by commercial insurance.14, 26 In an evaluation of the timing of just 2 complex palliative procedures that require surgery early in life, bidirectional Glenn and Fontan stages of single-ventricle palliation at the Duke University Medical Center, black children underwent the Glenn procedure at a median age of 11 months vs 5 months for whites.28 Black children underwent the Fontan procedure at a median age of 60 months and white children at 36 months. A further evaluation of the influence of insurance coverage on mortality after congenital heart disease surgery was accomplished in a retrospective cohort study using hospital discharge data from 5 states between 1992 and 1996.27 In 1996, children with Medicaid, more commonly covering minority racial groups, had a higher risk of death than those with commercial or managed care insurance. Of interest in light of the previous study results, Medicaid patients had a higher risk of death than those with commercial insurance at both higher- and lower-mortality institutions. It is possible that children covered by Medicaid are referred later to a pediatric cardiologist. Other considerations for higher postsurgical mortality among minority racial groups are language barriers that prevent patients from reporting symptoms earlier, lack of regular checkups in Medicaid groups, poor prenatal care, and intrauterine growth retardation.27 From a database from 2784 institutions in 27 states, a more recent analysis of racial and ethnic disparities in mortality following congenital heart surgery was investigated.28 As in previous analyses, black children had a higher death rate than whites (Oodds ratio, 1.65; P=.003] (Table V).28 Hispanic children had an insignificantly higher death rate than non-Hispanic whites. Adjustment for sex, income, and region continued to demonstrate a significantly higher postsurgical mortality in blacks (odds ratio, 1.76) but also in Hispanics (odds ratio, 1.34) compared with non-Hispanic whites. In this evaluation, insurance did not appear to play a role in sex differences, although blacks and Hispanics had higher rates of Medicaid insurance (56% each) compared with non-Hispanic whites (23%). Although Medicaid patients exhibited a trend toward higher mortality in unadjusted analyses, this difference was minimal after adjustment for risk factors. This lack of insurance impact compared with previous analyses may have been due to state-wide children’s health care programs of more recent vintage than previously, or the more comprehensive national study in this case. Significant regional variations were seen in mortality risk for blacks but not Hispanics. For example, only in the Northeast was mortality risk higher for blacks vs whites, and it was not significantly increased in other regions. ConclusionsRacial differences in congenital heart disease mortality generally and surgical mortality more specifically may be caused by a combination of genetic and environmental factors. These could include differences in prenatal care affecting intrauterine growth and development, disproportionate variations in the prevalence of diabetes and age of the mother, differences in medical training of physicians attending different racial groups, differences in mortality rates in hospitals serving minority groups, language barriers, and other factors that affect access to acceptable medical care. As with other aspects of cardiovascular disease in special groups, better access to medical care and focus on risk factor interventions need to be accomplished to decrease such disparities in outcome.