Congenital heart disease refers to a range of possible heart defects.

The following defects are described below:

• aortic valve stenosis 
• coarctation of the aorta 
• Ebstein's anomaly 
• patent ductus arteriosus 
• pulmonary valve stenosis 
• septal defects – including atrial septal defects and ventricle septal defects
• single ventricle defects – including tricuspid atresia and hypoplastic left heart syndrome
• tetralogy of Fallot 
• total anomalous pulmonary venous connection
• transposition of the great arteries 
• truncus arteriosus 

Aortic valve stenosis

Aortic valve stenosis is an uncommon and serious type of congenital heart defect. It accounts for around 5% of cases of congenital heart disease.

In aortic valve stenosis, the aortic valve that controls the flow of blood out of the main pumping chamber of the heart (the left ventricle) to the body's main artery (the aorta) is narrowed. This affects the flow of oxygen-rich blood away from the heart towards the rest of the body and means the muscle thickens because the pump has to work harder.

Coarctation of the aorta

Coarctation of the aorta (CoA) is where the main artery (the aorta) has a narrowing, which means that less blood can flow through it.

CoA accounts for around 10% of cases of congenital heart disease. It can occur by itself or in combination with other types of heart defects, most commonly a ventricular septal defect or a type of defect known as a patent ductus arteriosus (see below).

In around half of all cases, the narrowing can be severe and will require treatment shortly after birth.

Ebstein's anomaly

Ebstein's anomaly is where the valve on the right side of the heart (the tricuspid valve), which separates the chambers called the right atrium and right ventricle, does not develop properly. This means blood can flow the wrong way within the heart.

Ebstein's anomaly can occur on its own, but it often occurs along with an atrial septal defect (see below).

It's estimated that Ebstein's anomaly accounts for less than 1% of congenital heart disease cases.

Patent ductus arteriosus

Patent ductus arteriosus (PDA) is a rare type of congenital heart disease, affecting around 5 in every 100,000 babies. It is where a connection between the main body artery and lung artery (the ductus arteriosus) doesn't completely close after birth as it's supposed to.

This means extra blood is pumped into the arteries of the lungs, forcing the heart and lungs to work harder.

Pulmonary valve stenosis

Pulmonary valve stenosis is a defect where the pulmonary valve, which controls the flow of blood out of the right heart pumping chamber (the right ventricle) to the lungs, is narrower than normal. This means the right heart pump has to work harder to push blood through the narrowed valve to get to the lungs.

Pulmonary valve stenosis accounts for around 10% of cases of congenital heart disease.

Septal defects

A septal defect is where there is an abnormality in the wall (septum) between the main chambers of the heart. The two main types of septal defect are outlined below.

Atrial septal defects

An atrial septal defect (ASD) is where there is a hole between the two filling chambers of the heart (the atria). It's a common type of congenital heart defect, affecting about 200 in every 100,000 babies.

When there is an ASD extra blood flows into the right side of the heart, causing it to stretch and enlarge.

Ventricular septal defects

A ventricular septal defect (VSD) is also a common form of congenital heart disease, affecting around 200 in every 100,000 babies. It occurs when there is a hole between the two pumping chambers of the heart (the left and right ventricles).

This means extra blood flow goes to the lungs and the left side of the heart, causing high pressure in the lungs and a stretch on the left-sided pumping chamber. Small holes often close by themselves eventually, but larger holes need to be closed by surgery.

Single ventricle defects

A single ventricle defect is where only one of the pumping chambers (ventricles) develops properly. Some of the more common single ventricle defects are described below.

Hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) is a rare type of congenital heart disease where the left side of the heart doesn't develop properly and is too small. This means not enough oxygenated blood can get through to the body. 

Without treatment HLHS can be fatal within a few weeks of birth, but nowadays complex heart operations can be performed to try to change this.

Tricuspid atresia

Tricuspid atresia is where the tricuspid heart valve has not formed properly. The tricuspid valve separates the filling chamber (atrium) and pumping chamber (ventricle) on the right side of the heart. As there is no blood flow into the right pumping chamber, the pump does not develop and is too small. 

It is estimated that 10 babies in every 100,000 are affected by tricuspid atresia.

Tetralogy of Fallot

Tetralogy of Fallot is a combination of several defects, affecting about 30 in every 100,000 babies.

The defects making up tetralogy of Fallot are:

• ventricular septal defect – a hole between the left and right ventricle
• pulmonary stenosis – narrowing of the pulmonary valve
• right ventricular hypertrophy – where the heart muscle is thick
• displaced aorta – where the aorta is not in its usual position coming out of the heart

Because of this combination of defects, oxygenated and non-oxygenated blood mixes, causing the overall oxygen in the blood to be lower than normal.

Total anomalous pulmonary venous connection (TAPVC)

Total anomalous pulmonary venous connection (TAPVC) occurs when veins taking oxygenated blood from the lungs to the heart are connected in the wrong place. They connect to the right side of the heart when they should be connected to the left side. Sometimes veins are also narrowed, and the condition can be fatal within a month after birth.

TAPVC is an uncommon type of congenital heart disease, affecting around 7 in every 100,000 babies.

Transposition of the great arteries

Transposition of the great arteries is relatively common, accounting for around 5% of cases of congenital heart disease.

It is where the pulmonary (lung artery) and main body artery (the aorta) are connected to the wrong pumping chamber. This leads to blood low in oxygen being pumped around the body.

Truncus arteriosus

Truncus arteriosus is an uncommon type of congenital heart disease, affecting around 5 in every 100,000 babies.

It is where the development of the two main arteries (the pulmonary and aorta) does not happen properly and remains a single vessel.

This results in too much blood being sent to the lungs which, over time, can cause breathing difficulties and damaged blood vessels inside the lungs.

The condition is usually fatal within a year of birth if not treated.