Keywords

1 Epidemiology of Congenital Heart Disease

Congenital heart disease is an array of anatomical defects that range from simple defects, which close spontaneously during early years of life, to complex cyanotic defects that necessitate early surgical repair. Incidence is approximately 7 confirmed cases per 1000 or 1 in every 145 babies born [1]. This figure obviously varies according to the population studied but is an approximation for many Western countries [2]. Table 1.1 illustrates the different congenital anatomical defects and corresponding prevalence.

Table 1.1 Incidence of congenital heart disease
Full size table

Around two-thirds of all congenital heart disease is diagnosed in infancy, 30% in children, and 10% in adults (those over 16 years of age). Nowadays, there are more adults with congenital lesions that need surveillance and re-intervention in their adult life, and this implicates the delivery of care in adult congenital heart disease service [3].

The delivery of service to congenital heart disease expands from pediatric age till transition into adult care service. Most adults with congenital heart lesions are usually seen by the pediatric cardiologist. These patients have been the beneficiaries of advances in pediatric cardiology and cardiac surgery services exemplified by the fact that 96% of children with congenital cardiac lesions who survive infancy will live to at least 15 years of age [4, 5].

Approximately 17% of congenital cardiac conditions occur in association with a recognized syndrome that “causes” the defect [3]. However, the genetic contribution to congenital lesions is much greater. Over the last decade, numerous genetic loci and chromosomal abnormalities have been identified for a whole range of conditions. One only needs to look at the recurrence rate for mothers with congenital heart disease to realize that familial and genetic factors contribute to many of the most common lesions.

There is, however, a great geographic variation regarding the incidence of CHD, which remains high in developing countries, located in Africa and Asia (up to 2.5%), and lower (about 1.2%) in most developed countries. This difference is mainly attributed to the establishment of fetal screening programs and termination of pregnancy in middle- and higher-income countries. The etiology of CHD is multifactorial, due to both genetic predisposition and environmental influences throughout fetal and early life [6]. Although Turner syndrome, trisomy 21, a 22q11 deletion, and other syndromes are seen in 20% of CHD cases, the majority of CHD is non-syndromic. In terms of environmental factors, maternal exposure to toxins and chemicals such as pesticides, herbicides, and lithium, smoking, alcohol, obesity, diabetes mellitus, malnutrition, rubella, and low socioeconomic status have been associated with increased risk of CHD.

There is a great genotype–phenotype heterogeneity with a high causative variance relative to low frequency of specific CHD phenotypes [7, 8], which renders disease classification difficult. CHD defects are classified as simple, moderate, or severe, in terms of complexity [9]. The most common CHD subtypes worldwide are the simple defects, atrial septal defect (ASD) and ventricular septal defect (VSD), which account for about one-third of CHD. On the other hand, the incidence of newborns with single ventricle physiology and other severe CHD types has declined over the past 30 years among all regions, likely associated with prenatal screening [10].

Over the last decades, major breakthroughs in pediatric cardiology, cardiac surgery, and interventional cardiology have dramatically improved the course of CHD, with a substantial decline in early mortality globally and especially in high-income countries [11]. In the 1950s, survival of children born with CHD was limited to 15%. Nowadays, more than 90% of these children survive well into adulthood. Therefore, there has been a shift in the disease landscape from infancy and childhood toward adulthood, with adults accounting for two-thirds of the CHD population. In the United States, there were an estimated 1.4 million adults with CHD, of a total CHD population of 2.4 million in 2010 [12].

Although mortality continues to decline, CHD is never cured and is present as a chronic condition with cumulative complications over the life span, magnified since birth [13]. Therefore, the field of adult CHD cardiology has emerged, in order to manage not only young or middle-aged adults but also patients with CHD over 60 years old. Many adult patients are afflicted by residual hemodynamic lesions and also face additional challenges such as pregnancy, acquired heart disease, and non-cardiac pathology, necessitating integrated multi-disciplinary care at expert centers [14]. There is, consequently, an increasing need in educating physicians, nurses, psychologists, and other personnel in order to provide high-quality lifelong services to this rising population.