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).

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.

Initially, a newborn with hypoplastic left heart may appear normal. Symptoms usually occur in the first few hours of life, although it may take up to a few days to develop symptoms. These symptoms may include:

• Lethargy
• Poor suckling and feeding
• Shortness of breath
• Rapid breathing
• Cold extremities
• Enlarged liver
• Poor pulse
• Pounding heart
• Bluish (cyanosis) or poor skin color
• Sudden death

In healthy newborns, bluish color occurs in hands and feet as a response to cold (this reaction is called peripheral cyanosis).

However, a bluish color observed in the chest or abdomen, lips, and tongue is abnormal (called central cyanosis) because it reflects lack of adequate levels of oxygen in the blood. This is secondary to the heart malformation and circulatory malfunction. Central cyanosis often increases with crying.

A physical exam may show signs of heart failure, liver enlargement, rapid breathing, and lethargy. Additionally, the pulse at various locations (wrist, groin, and others) is usually very weak. There are usually abnormal heart sounds when listening to the chest.

Tests may include:

• ECG shows enlargement of the right ventricle of the heart
• X-ray of the chest may show signs of other birth defects
• Echocardiogram
• Cardiac catheterization

Once the diagnosis of hypoplastic left heart is made, the baby will be admitted to the neonatal intensive care unit. A breathing machine (ventilator) may be needed to help the baby breathe. A medicine called prostaglandin E1 is used to maintain circulation of blood to the body.

These measures do not solve the problem. The condition always requires surgery.

The first surgery, called the Norwood operation, occurs within the first few days of life. Stage I of the Norwood procedure consists of building a new aorta, and an artificial shunt is inserted to maintain blood flow to the lungs.

Afterwards, the baby usually goes home. The child will need to take one or more daily medicines and be closely followed by a pediatric cardiologist, who will determine when the second stage of surgery should be done.

Stage II of the operation is called the Glenn shunt or Hemifontan procedure. This procedure connects half of the veins carrying blue blood from the body (the superior vena cava) directly to blood vessels to the lungs to get oxygen. The surgery is usually done when the child is 4 - 6 months of age.

During stage I and II, the child may still appear somewhat blue (cyanotic).

Stage III, the final step, is called the Fontan procedure. The remainder of the veins carrying blue blood from the body (the inferior vena cava) is connected directly to the blood vessels to the lungs, and the right ventricle now serves as the only pumping chamber for the heart. This surgery is usually performed between the ages of 18 months and 3 years of age. After this final step, the baby is no longer blue (cyanotic).

Some patients may need more surgeries in their 20s or 30s if they develop hard to control arrhythmias or other complications of the Fontan procedure.

In some hospitals, heart transplantation is considered a better choice than the 3-step surgery process. However, there are few donated hearts available for small infants.

If left untreated, hypoplastic left heart syndrome is fatal. Survival rates for the staged repair continue to rise as surgical technique and postoperative management improve. Survival after the first stage is more than 75%.

It is important to note that the size and function of the right ventricle are important determinants of outcome after surgery.

Complications include:

• Irregular, fast heart rhythms (arrhythmias)
• Chronic diarrhea (from a disease called protein loosing enteropathy)
• Heart failure
• Fluid in the abdomen (ascites) and in the lungs (pleural effusion)
• Blockage of the artificial shunt
• Strokes and other neurological complications
• Sudden death

If your infant has new changes in breathing patterns, eats less (decreased feeing), or has skin or mucous membranes that are turning blue (cyanotic), contact your health care provider immediately.

There is no known prevention for hypoplastic left heart syndrome. As with many congenital diseases, the causes of hypoplastic left heart syndrome are uncertain and have not been linked to a mother's disease or behavior.

Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 8th ed. St. Louis, Mo; WB Saunders; 2007.