Congenital heart disease covers a wide spectrum from small defects, which may be totally asymptomatic and compatible with a normal lifespan, to more severe forms which require urgent intervention. Many defects are possible but most defects either obstruct flow of blood in the heart or in vessels near to it or cause blood to take an abnormal route through the heart. More rarely only one ventricle may be present, or the right or left side of the heart has failed to form properly (hypoplastic heart). Significant amounts of blood shunting from right to left without traversing the lungs causes cyanotic congenital heart disease.
This is a companion discussion topic for the original article at https://patient.info/doctor/paediatrics/congenital-heart-disease-in-children