There are over 30 different types of congenital heart disease that fall into 3 main categories:
Septal defects- there is a hole between the chambers of the heart (atrial, ventricular or atrioventricular), that places extra strain on the chambers causing symptoms such as fatigue and shortness of breath.
Obstruction defects- there is a partial or sometimes complete blockage of the flow of blood through the various chambers of the heart (e.g. aortic or pulmonary stenosis), which can cause symptoms such as chest pain and dizziness.
Cyanotic heart disease- one or more defects within the heart leads to a lack of oxygen being pumped around the body which can trigger symptoms such as cyanosis (blue discolouration of the skin), breathing difficulties and persisting tiredness.
85% of children with congenital heart defects are now living into adulthood with relatively normal lives. Causes are unclear though are thought to include development problems during pregnancy, e.g. maternal rubella, alcohol, illegal drugs and over-the-counter medications, maternal diabetes and genetic conditions such as Down's syndrome. The following diagram illustrates a ventricular septal defect and the potential passageway of deoxygenated blood that can bypass going to the lungs for oxygen and enter into the left ventricle directly: