Adults With Congenital Heart Disease: A Growing Population

Global Estimates of Incidence and Birth Prevalence of Congenital Heart Disease

The product of CHD incidence and survival rates determines CHD prevalence at all ages. Understanding of determinants of CHD incidence underscores the challenges of measurement, even using empirical data. The exact incidence of CHD cannot be accurately determined because it would require tracking the number of new cases of CHD in utero, from conception. The best proxy to estimate incidence of new CHD cases each year is birth prevalence . Reported birth prevalence rates of CHD vary widely according to which lesions are included and in what geographic area of the world they are measured. In the United States, data from the Centers for Disease Control and Prevention (CDC) using the Metropolitan Atlanta Congenital Defects Program from 1998 to 2005 identified an overall prevalence of 8.14/1000, meaning that 3240 births out of 398,140 were affected by CHD. The most common forms of CHD were perimembranous ventricular septal, muscular ventricular septal, and secundum atrial septal defects. Tetralogy of Fallot, the most common cyanotic CHD, had twice the prevalence of the transposition of the great arteries. In Europe, the European Surveillance of Congenital Anomalies (EUROCAT) database is a population-based monitoring system for CHD that sources data from at least 16 countries. This registry includes cases based on live births, late fetal death/stillbirths, and terminations of pregnancy for fetal anomaly. The reported total CHD prevalence based on 26,598 cases of CHD was 8.0 per 1000 births ranging across countries from 5.36 to 15.32 per 1000 births) with live-birth prevalence rates of 7.2 per 1000 births. A systematic review of birth prevalence for the eight most common CHD lesions until 2010 provided a worldwide overview. After 1995, the reported birth prevalence of CHD was 9.1 per 1000 live births with significant difference in birth prevalence between different World Bank income groups and geographical areas. Compared with all other continents including Africa, the reported total CHD prevalence was highest in Asia (9.3 per 1000 live births). High-income countries consistently reported higher CHD birth prevalence rates (8.0 per 1000 live births) relative to lower- to middle-income countries (6.9 per 1000 live births). Pregnancy termination and prevention as well as prenatal care affect both pathways and measures of birth prevalence rates of CHD. The EUROCAT registry showed perinatal mortality rates of 0.25 per 1000 live births. Pregnancy terminations for fetal anomaly after prenatal diagnosis varied widely, ranging from under 0.3 to 1.1 per 1000 births. In industrialized countries, birth rates of CHD may also be affected by other factors, including mandatory folate supplementation during pregnancy, thereby decreasing the birth rate of severe CHD. Geographical variations are also noted with respect to the prevalence of CHD subtypes. For example, compared with other continents, Asia reported a higher prevalence of pulmonary outflow obstructions and lower rates of transposition of the great arteries at birth. Thus global spread in measurement of birth prevalence of CHD reflects a variety of pathways related to biology, ascertainment, prevention, and termination as well as factors related to health systems delivery and surveillance, with the most commonly reported birth prevalence of CHD in industrialized countries centering around 8 per 1000 live births.

Changes in Mortality, Survival, and Life Expectancy in the Congenital Heart Disease Population

Mortality rates of CHD patients in the United States were measured from 1979 through to 1997 using statistics from the CDC. Almost half of overall CHD mortality occurred in infancy. CHD mortality rates decreased by 40% for all ages, especially among children younger than 5 years. Variations in mortality are the result of differences in type of defect, race, age, and sex. Using data extracted from US death certificates from 1999 to 2006, and population counts from the US Census as the denominator, annual CHD mortality rates by age at death, sex, and race/ethnicity were calculated for individuals aged 1 year or older. Over the same period, mortality rates from CHD fell by 24% overall among all race/ethnicity groups surveyed. However, some disparities persisted; rates were consistently higher among non-Hispanic blacks relative to non-Hispanic whites. Infant mortality accounted for 48% of CHD mortality rates, and among those who survived their first year of life, 76.1% of deaths occurred in adulthood (aged 18 years and older). These findings underline the need for more consistent access to care and continued monitoring as patients age. Using a Canadian population-based database, temporal trends in mortality were compared between 1987–1988 and 2004–2005. The study population comprised 8123 deaths over 1,008,835 patient-years of follow-up. In 1987–1988, peak mortality was highest during infancy, with a second peak in adulthood. By 2004–2005, overall mortality had declined by 31%, and the age distribution of death was no longer bimodal because there was a shift in mortality toward older age. In addition, for individuals younger than 65 years, adjusted mortality rates declined in all age categories.

Decreasing mortality rates have been associated with improved survival rates for the CHD population . Survival in critical CHD cases was analyzed using a retrospective US population-based cohort of infants born with CHD between 1979 and 2005, identified through the Metropolitan Atlanta Congenital Defects Program. Although survival to adulthood improved significantly over time, it remained significantly lower for individuals with critical CHD compared with those with noncritical CHD; 69% compared with 95% respectively. In Europe, an analysis of survival trends by defect type and cohort was performed in Belgium using the clinical and administrative records of 7497 CHD patients born between 1970 and 1992. Overall survival rates to age 18 years for children born between 1990 and 1992 were nearly 90%, showing considerable improvement over previous decades. Within this cohort, survival to adulthood for individuals with mild heart defects was 98%, while those with moderately complex and severely complex heart defects had survival rates of 90% and 56%, respectively. As a result of decreasing mortality and increasing survival rates in all forms of CHD, including severe CHD, there is a substantial increase in the median age of patients with severe CHD, rising from 11 years in 1985 to 17 years in 2000, and to 25 years in 2010 ( Fig. 1.2 ).

Although often used interchangeably, from a conceptual and computational point of view, survival and life expectancy are distinct. Life expectancy can be obtained by calculating the area under a survival curve. The gain in life expectancy is the averaged difference between survival curves with or without a specified intervention at a time point or age. Life expectancy is measured in life-years as years lived in health or disability at or from a specific age. This can be expressed as a disability-adjusted life expectancy (DALE) reflecting life-years of health or disability-adjusted life years (DALYs) reflecting life-years of disability. For young adults with CHD, life expectancy is a more relevant measure of impact of disease burden, yet such data for CHD are scant or nonexistent. For example, a man born with a univentricular heart in 1985, is being considered for a Fontan revision. The risks and benefits of intervention are being discussed. The patient and his wife are considering starting a family. They would like to know what the future holds and how long he might be expected to live. What informative data can be provided? Although survival rates with different subtypes of Fontan procedures can be cited and are reassuring in that they represent progress, what does this mean for the patient? The family wants to know how long the patient can be expected to live from his current adult age and if he will be healthy or disabled in any way. Specifically, they would like to know how many healthy years could be gained on his life if an operation is performed. Particularly relevant to young adults, there is a need to generate data that would inform such decisions in ACHD populations.

Thus, observations in North America and Europe are consistent in terms of improved mortality and survival rates of infant and childhood populations. Although great progress has been made, these findings underscore the work that lays ahead with respect to improvement of long-term outcomes of the CHD population into adulthood in terms of survival and life expectancy adjusted to relevant measures of quality of life.