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 present at birth (congenital).

Causes

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

As with most congenital heart defects, there is no known cause. About 10% of babies with hypoplastic left heart syndrome also have other birth defects.

The problem develops before birth when the left ventricle and other structures do not grow properly, including the:

• Aorta: the blood vessel that carries oxygen-rich blood from the left ventricle to the entire body
• Entrance and exit of the ventricle
• Mitral and aortic valves

This causes the left ventricle and aorta to be poorly developed, or hypoplastic. In most cases, the left ventricle and aorta are much smaller than normal.

In babies 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. The right ventricle can support the circulation to both the lungs and the body for a while, but this extra workload eventually causes the right side of the heart to fail.

The only possibility of survival is a connection between the right and the left side of the heart, or between the arteries and pulmonary arteries (the blood vessels that carry blood to the lungs). Babies are normally born with 2 of these connections:

• Foramen ovale (a hole between the right and left atrium)

  Foramen

  Patent foramen ovale (PFO) is a hole between the left and right atria (upper chambers) of the heart. This hole exists in everyone before birth, but ...

  

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• Ductus arteriosus (a small blood vessel that connects the aorta to the pulmonary artery)

  Ductus arteriosus

  Patent ductus arteriosus (PDA) is a condition in which the ductus arteriosus does not close. The word "patent" means open. The ductus arteriosus is ...

  

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Both of these connections normally close on their own a few days after birth.

In babies with hypoplastic left heart syndrome, blood leaving the right side of the heart through the pulmonary artery travels through the ductus arteriosus to the aorta. This is the only way for blood to get to the body. If the ductus arteriosus is allowed to close in a baby with hypoplastic left heart syndrome, the baby may quickly die because no blood will be pumped to the body. Babies with known hypoplastic left heart syndrome are usually started on a medicine to keep the ductus arteriosus open.

Because there is little or no flow out of the left heart, blood returning to the heart from the lungs needs to pass through the foramen ovale or an atrial septal defect (a hole connecting the collecting chambers on the left and right sides of the heart) back to the right side of the heart. If there is no foramen ovale, or if it is too small, the baby could die. Babies with this problem have the hole between their atria opened, either with surgery or using a thin, flexible tube (heart catheterization).

Symptoms

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

• Bluish ( cyanosis ) or poor skin color

  Cyanosis

  Cyanosis is a bluish color to the skin or mucous membrane that is usually due to a lack of oxygen in the blood.

  

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• Cold hands and feet (extremities)
• Lethargy
• Poor pulse
• Poor suckling and feeding
• Pounding heart
• Rapid breathing
• Shortness of breath

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

A bluish color in the chest or abdomen, lips, and tongue is abnormal (called central cyanosis). It is a sign that there is not enough oxygen in the blood. Central cyanosis often increases with crying.

Exams and Tests

A physical exam may show signs of heart failure:

• Faster than normal heart rate
• Lethargy
• Liver enlargement
• Rapid breathing

Also, the pulse at various locations (wrist, groin, and others) may be very weak. There are often (but not always) abnormal heart sounds when listening to the chest.

Tests may include:

• Cardiac catheterization

  Cardiac catheterization

  Cardiac catheterization involves passing a thin flexible tube (catheter) into the right or left side of the heart. The catheter is most often insert...

  

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• ECG

  ECG

  An electrocardiogram (ECG) is a test that records the electrical activity of the heart.

  

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• Echocardiogram

  Echocardiogram

  An echocardiogram is a test that uses sound waves to create pictures of the heart. The picture and information it produces is more detailed than a s...

  

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• X-ray of the chest

  X-ray of the chest

  A chest x-ray is an x-ray of the chest, lungs, heart, large arteries, ribs, and diaphragm.

  

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Treatment

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 keep blood circulating to the body by keeping the ductus arteriosus open.

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

The first surgery, called the Norwood operation, occurs within the baby's first few days of life. The Norwood procedure consists of building a new aorta by:

• Using the pulmonary valve and artery
• Connecting the hypoplastic old aorta and coronary arteries to the new aorta
• Removing the wall between the atria (atrial septum)
• Making an artificial connection from either the right ventricle or a body-wide artery to the pulmonary artery to maintain blood flow to the lungs (called a shunt)

Afterward, the baby goes home in most cases. The child will need to take 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 hemi-Fontan procedure. This procedure connects the major vein carrying blue blood from the top half of the body (the superior vena cava) directly to blood vessels to the lungs (pulmonary arteries) to get oxygen. The surgery is most often done when the child is 4 to 6 months of age.

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

Stage III, the final step, is called the Fontan procedure. The rest of the veins that carry blue blood from the body (the inferior vena cava) are connected directly to the blood vessels to the lungs. The right ventricle now serves only as the pumping chamber for the body (no longer the lungs and the body). This surgery is usually performed when the baby is 18 months to 4 years old. After this final step, the child is no longer cyanotic and has a normal oxygen level in the blood.

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

Some doctors consider heart transplantation an alternative to the 3 step surgery. But there are few donated hearts available for small infants.

Outlook (Prognosis)

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

The child's outcome after surgery depends on the size and function of the right ventricle.

Possible Complications

Complications include:

• Blockage of the artificial shunt
• Chronic diarrhea (from a disease called protein-losing enteropathy)
• Fluid in the abdomen ( ascites ) and in the lungs ( pleural effusion ) 

  Ascites

  Ascites is the build-up of fluid in the space between the lining of the abdomen and abdominal organs.

  

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  Pleural effusion

  A pleural effusion is a buildup of fluid between the layers of tissue that line the lungs and chest cavity.

  

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• Heart failure

  Heart failure

  Heart failure is a condition in which the heart is no longer able to pump oxygen-rich blood to the rest of the body efficiently. This causes symptom...

  

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• Irregular, fast heart rhythms (arrhythmias)
• Strokes and other nervous system complications
• Sudden death

When to Contact a Medical Professional

Contact your health care provider right away if your infant:

• Eats less (decreased feeding)
• Has blue (cyanotic) skin
• Has new changes in breathing patterns

Prevention

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.