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Page Contents:
1. What is Hypoplastic Left Heart Syndrome
2. Symptoms
3. Causes
4. Risk factors
5. Diagnosis
6. Tests
7. Treatments
8. Complications
9. long-term expectation
10. Sources and references

What is Hypoplastic Left Heart Syndrome?

Hypoplastic left heart syndrome is a rare heart defect present at birth (congenital). In this condition, the left side of the heart is extremely underdeveloped.
 
In a child with hypoplastic left heart syndrome, the structures on the left side of the heart are very underdeveloped. The left side of the heart gets the oxygen rich blood from the lungs. It then pumps the blood out to the body.
 
Treatment of hypoplastic left heart syndrome requires medication to prevent closure of the connection (ductus arteriosus) between the right and left sides of the heart. Plus, either surgery or a heart transplant is necessary. Advances in care have improved the outlook for babies born with this condition.

Symptoms of hypoplastic left heart syndrome

In most cases, children with hypoplastic left heart syndrome appear healthy at birth.
 
When a baby is not diagnosed during pregnancy, symptoms may develop within the first few hours or days of life:
 
*rapid breathing or shortness of breath
*rapid heartbeat or pounding heart
*poor suckling and feeding
*cold extremities (poor perfusion)
*blue color of the skin, lips, and nailbeds (cyanosis)
*weakness

Causes of hypoplastic left heart syndrome

HLHS is the result of under-development of sections of the fetal heart during the first eight weeks of pregnancy.
 
The cause of HLHS is complex and involves many factors. In some families, there is a genetic predisposition or tendency towards developing HLHS, but most families have no prior history of congenital heart disease. HLHS comes in many different forms. Some patients have a primary problem with their left ventricular heart muscle, some with the aortic valve, and some with the mitral valve. Many have problems with all three.

Risk factors

The causes of HLHS among most babies are unknown. Some babies have heart defects because of changes in their genes or chromosomes. A combination of genes and other risk factors may increase the risk for HLHS. These factors can include things in a mother’s environment, what she eats or drinks, or the medicines she uses.

Diagnosis

A healthcare provider can make a hypoplastic left heart syndrome diagnosis with information from harmless imaging.
 
Your provider may do this during your pregnancy or soon after your baby is born.
 
During pregnancy, healthcare providers use painless and non-invasive imaging methods such as:
 
*Ultrasound.

*Fetal echocardiogram (ultrasound) to evaluate your baby’s heart before birth.

After your baby is born, healthcare providers diagnose the condition by observing symptoms and examining test results. They may hear a heart murmur while using a stethoscope to listen to your baby’s heart. This means blood isn’t flowing the way it should.

Tests to diagnose hypoplastic left heart syndrome

Tests for a hypoplastic left heart syndrome diagnosis may include:
 
*Chest X-ray: This shows the size and shape of your baby’s heart and lungs.
*Echocardiogram: This ultrasound shows internal heart structures.
*Electrocardiogram (EKG): This measures electrical changes during a heartbeat.
*Pulse oximetry screening: This tells how much oxygen is in your baby’s bloodstream.

Treatments

Treatments for HLHS might include the following:
 

_Medicines

Some people with HLHS will need medicines to:
 
*Strengthen the heart muscle
*Lower their blood pressure
*Help the body get rid of extra fluid
 

_Nutrition

Some babies with HLHS become tired while feeding and do not eat enough to gain weight. To make sure babies have a healthy weight gain, a special high-calorie formula might be prescribed. Some babies become extremely tired while feeding and might need to be fed through a feeding tube.
 

_Surgery

Soon after a baby with HLHS is born, multiple surgeries done in a particular order are needed. These surgeries will help increase blood flow to the body and bypass the poorly functioning left side of the heart. The surgeries help the right ventricle to become the main pumping chamber for blood to reach the body.
These surgeries do not cure HLHS but help restore heart function. Sometimes medicines are given to help treat symptoms of the defect before or after surgery. Surgery for HLHS usually is done in three separate stages:
 

1. Norwood procedure. This surgery usually is done within the first 2 weeks of a baby’s life. Surgeons create a “new” aorta and connect it to the right ventricle. They also place a tube from either the aorta or the right ventricle to the vessels supplying the lungs (pulmonary arteries). Thus, the right ventricle can pump blood to both the lungs and the rest of the body. This can be a very challenging surgery. After this procedure, an infant’s skin still might look bluish because oxygen-rich and oxygen-poor blood still mix in the heart.

 

2. Bi-directional Glenn Shunt procedure. This surgery usually is performed when an infant is 4 to 6 months of age. This procedure creates a direct connection between the pulmonary artery and the superior vena cava. The superior vena cava is a vessel that returns oxygen-poor blood from the upper part of the body to the heart. This new connection reduces the work of the right ventricle by allowing blood from the body to flow to the lungs.

 

3. Fontan procedure. This surgery is usually done between 18 months and 3 years of age. Doctors connect the pulmonary artery and the inferior vena cava. The inferior vena cava is the vessel that returns oxygen-poor blood from the lower part of the body to the heart. This allows the rest of the blood coming back from the body to go to the lungs. Once this procedure is complete, oxygen-rich and oxygen-poor blood no longer mix in the heart. As a result, an infant’s skin will no longer look bluish.

Complications of the treatment

Some children may not make it from one surgery to the next. Also, they may have problems after each surgery, such as:
 
*Issues with their right ventricle not working right.
*An aortic valve leak.
*Liver disease.
*Abnormal heart rhythms.
*Blood clots.
*Infection.
*Trouble eating.
*Seizures.
*Kidney problems.
*Cardiac arrest.

What to expect long-term

Surgical repairs for HLHS are not a cure. Infants with HLHS may have lifelong complications. They will need routine checkups with a heart doctor to monitor their progress.
 
If the HLHS defect is very complex, or the heart becomes weak after the surgeries, a heart transplant may be needed. Infants who receive a heart transplant will need to take medicines for the rest of their lives. These medications may prevent their body from rejecting the new heart.
Sources and references

https://www.cdc.gov/heart-defects/about/hypoplastic-left-heart-syndrome.html
https://www.childrenshospital.org/conditions/hypoplastic-left-heart-syndrome
https://my.clevelandclinic.org/health/diseases/12214-hypoplastic-left-heart-syndrome-hlhs
https://medlineplus.gov/ency/article/001106.htm
https://kidshealth.org/en/parents/hypoplastic-heart.html
https://www.cincinnatichildrens.org/health/h/hlhs
https://www.chop.edu/conditions-diseases/hypoplastic-left-heart-syndrome-hlhs
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