Definition of Hypoplastic left heart syndrome:

Hypoplastic left heart syndrome occurs when parts of the left side of the heart (mitral valve, left ventricle aortic valve, and aorta) do not develop completely. The condition is congenital (present at birth).

Causes, incidence, and risk factors:

Hypoplastic left heart is a rare type of congenital heart disease. It is more common in males than in females.

The problem develops before birth when there is not enough growth of the left ventricle and other structures (aortic and mitral valves that guard the exit and entrance of the ventricle and the aorta, the blood vessel that carries oxygenated blood from the left ventricle to the entire body).

In patients with this condition, the left side of the heart is unable to send enough blood to the body. As a result, the right side of the heart must maintain the circulation for both the lungs and the body. This extra workload eventually causes the heart to fail.

The only possibility of survival is a connection between the right and the left side of the heart its blood vessels, through which blood may pass. This is called a shunt. Babies are normally born with two of these connections (the foramen ovale and the ductus arteriosus), which normally close on their own a few days after birth.

If ductus arteriosus is allowed to close in a baby with hypoplastic left heart syndrome, however, the patient will quickly die because no blood will be pumped to the body.

As with most congenital heart defects, there is no known cause. Around 10% of patients with hypoplastic left heart syndrome will have other birth defects.