Congenital heart diseaseCongenital heart disease (CHD) is the most common congenital malformation accounting for one-third of all congenital abnormalities with an incidence of 7–10 per 1000 live births. Congenital heart diseaseCongenital heart disease may occur in isolation (non-syndromic) with no family history of CHD. A monogenic cause in this situation is very rare. In a few families there is clearly a monogenic (but non-syndromic) cause for the congenital heart diseaseCongenital heart disease as several family members may be affected. When CHD is present in association with other malformations or intellectual disability (syndromic), a monogenic or chromosomal abnormality is often the cause. The geneticsGenetics of congenital heart diseaseCongenital heart disease is highly complex. Pathogenic variants in different genes can cause an identical malformation, whilst identical pathogenic variants in the same gene can result in a spectrum of cardiac malformations. Environmental/teratogenic factors play a significant role in the development of cardiac malformations. Prenatal diagnostic techniques, isolated, familial, environmental/teratogenic causes of CHD will be discussed in this chapter. In addition, syndromic diagnosesDiagnosis such as Noonan syndromeSyndrome, tuberose sclerosis, cardiomyopathyCardiomyopathy and arrhythmiasArrhythmia will be discussed.