A congenital heart defect (CHD) is a defect in the structure of the heart and great vessels of a newborn. Most heart defects either obstruct blood flow in the heart or vessels near it or cause blood to flow through the heart in an abnormal pattern, although other defects affecting heart rhythm (such as long QT syndrome) can also occur. Heart defects are among the most common birth defects and are the leading cause of birth defect-related deaths.
Epidemiology
Epidemiology is the study of factors affecting the health and illness of populations, and serves as the foundation and logic of interventions made in the interest of public health and preventive medicine. It is considered a cornerstone methodology of public health research, and is highly regarded in evidence-based medicine for identifying risk factors for disease and determining optimal treatment approaches to clinical practice.
In the work of communicable and non-communicable diseases, the work of epidemiologists range from outbreak investigation to study design, data collection and analysis including the development of statistical models to test hypotheses and the documentation of results for submission to peer-reviewed journals. Epidemiologists may draw on a number of other scientific disciplines such as biology in understanding disease processes and social science disciplines including sociology and philosophy in order to better understand proximate and distal risk factors.
Etiology
The cause of most congenital heart defects is unknown.
Where a cause is known, it may be of a multifactorial origin and/or a result of genetic predisposition and environmental factors.
Known genetic causes of heart disease includes chromosomal abnormalities such as trisomies 21, 13, and 18, as well as a range of newly recognised genetic point mutations, point deletions and other genetic abnormalities as seen in syndromes such as CATCH 22, familial ASD with heart block, Alagille syndrome, Noonan syndrome, and many more.
Known antenatal environmental factors include maternal infections (Rubella), drugs (alcohol, hydantoin, lithium and thalidomide) and maternal illness (diabetes mellitus, phenylketonuria, and systemic lupus erythematosus).
Relation of congenital heart defects with sex
According to “Teratological rule of sexual dimorphism” (V. Geodakian, 1970), inborn anomalies that have atavistic nature appear more frequently among females, and futuristic anomalies appear among males. This rule was applied to explain differences in sex ratio observed for congenital heart defects.
In the 32,000 diagnoses of “female” malformations, those relating to the heart of the embryo and to the phylogenetic human predecessors predominated (Table). The most well-defined female’s defects are patent ductus arteriosus (1♂ : 2.72♀), Lutembacher disease (1♂ : 2.1♀), and ostium secundum(1♂ : 1.84♀).
