What are other Names for this Condition? (Also known as/Synonyms)

• Aortic and Mitral Atresia with Hypoplastic Left Heart Syndrome
• HLHS (Hypoplastic Left Heart Syndrome)

What is Hypoplastic Left Heart Syndrome? (Definition/Background Information)

• Congenital heart defects are relatively common birth defects involving the heart, and these may be of several types. Hypoplastic Left Heart Syndrome (HLHS) is a rare condition that describes a critical congenital heart defect in which the left side of the heart remains underdeveloped, and a hole is typically seen in the septum, the wall that divides the upper chambers of the heart (the atria)
• Hypoplastic Left Heart Syndrome affects individuals at birth (congenital manifestation) and is slightly more commonly observed in males than females. A family history of the condition is a predisposing factor for this heart condition. However, the exact cause of Hypoplastic Left Heart Syndrome development is unknown
• The signs and symptoms of Hypoplastic Left Heart Syndrome arise as a consequence of the deformed left side of the heart, and may include restricted blood flow from the lungs to other parts of the body, bluish-gray skin, and cold hands and feet
• The condition may be diagnosed before/after birth using a special ultrasound technique called an echocardiogram, which helps visualize the heart. In a majority of cases, children with Hypoplastic Left Heart Syndrome may need multi-stage surgical treatments. Without suitable and immediate management, the condition can be fatal within the first few weeks of life

Who gets Hypoplastic Left Heart Syndrome? (Age and Sex Distribution)

• Hypoplastic Left Heart Syndrome (HLHS) is a rare disorder that affects 1 in 100,000 individuals worldwide. However, it accounts for about 7-9% of all heart defects detected at birth
• The disorder is congenital in nature, meaning that the children are affected at birth
• It affects males more than females in a 1.7:1 ratio
• HLHS can affect individuals of any racial group, ethnicity, or geographic location

What are the Risk Factors for Hypoplastic Left Heart Syndrome? (Predisposing Factors)

• A positive family history of Hypoplastic Left Heart Syndrome (HLHS) is identified as a risk factor for the condition
• No other specific risk factors have been recognized for HLHS

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Hypoplastic Left Heart Syndrome? (Etiology)

• The cause of development of Hypoplastic Left Heart Syndrome is currently not well understood. The features of this complex heart condition may include:
  • Abnormally-formed valves - aortic valve and/or mitral valve
  • Abnormally-formed left ventricle
  • Small or underdeveloped ascending aorta
  • Presence of atrial septal defect (ASD)
• Research has indicated a variety of potential environmental and genetic factors for Hypoplastic Left Heart Syndrome, although these are not confirmed yet
• It is also believed that what the expectant mother consumes, such as food, drink, or even some medications, may be contributive

What are the Signs and Symptoms of Hypoplastic Left Heart Syndrome?

Hypoplastic Left Heart Syndrome may be detected before birth using ultrasound studies. The signs and symptoms may arise soon after birth and are directly associated with the underdevelopment of the left side of the heart. These may include:

• Difficult or rapid breathing; pounding heart
• Poor feeding
• Cold hands and feet
• A high-pitch noise made while inhaling
• Grayish-blue discoloration of the skin for the first 48 hours of life
• Fluid buildup in the heart, lungs, and some body tissues
• Buildup of excessive metabolic acids in blood and other body tissues
• In all cases there is restricted blood flow from the lungs to the heart and to other parts of the body

It is likely for heart failure to occur in infants if the natural connection between the right and left side of the heart is closed. The following are indications of heart failure in a child with Hypoplastic Left Heart Syndrome:

• Abnormally high pulse and respiration rate
• Respiratory distress
• Enlarged liver
• Cool clammy pale skin
• Dilated pupils

How is Hypoplastic Left Heart Syndrome Diagnosed?

A diagnosis of Hypoplastic Left Heart Syndrome (HLHS) may be made following a physical examination and a careful evaluation of the child’s medical and family history. Distinguishing findings and multiple specialized tests are used to diagnose HLHS such as:

• Assessment of the presenting signs and symptoms, particularly pale skin of the child, breathing difficulties, weak pulse, and rapid pounding of the heart
• X-ray examinations of the chest
• Fetal echocardiogram: A special ultrasound scan to study the structure and function of the heart prenatally
• Newborn pulse oximetry screening may help the healthcare suspect the condition prior to symptom presentation
• Cardiac catheterization: Installation of a catheter from a peripheral artery to the heart
• MRI scan studies of the heart

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Hypoplastic Left Heart Syndrome?

Hypoplastic Left Heart Syndrome can be fatal within the first weeks of life without surgery. With surgery, most infants survive, but complications may be noted later in life that may include:

• Tiring easily during exercise
• Abnormal heart rhythms
• Fluid buildup in the abdomen, lungs, legs and feet
• Strokes or other nervous system complications
• Blockage of artificial shunt
• Heart failure
• Need for additional surgeries
• Severe emotional and psychological stress for the parents/caregivers

How is Hypoplastic Left Heart Syndrome Treated?

Once a baby is diagnosed with Hypoplastic Left Heart Syndrome, they are normally admitted into an intensive care unit; the use of a breathing machine may be needed. A medication, known as prostaglandin E1, which allows blood to circulate normally keeping the heart ducts open, is administered. Leading up to the surgery, the child will also be given fluids through a vein and food through a feeding tube.

• Treatment for Hypoplastic Left Heart Syndrome almost always includes surgery, and the first one is typically planned within the baby’s first few days of life
  • The first surgery is the Norwood procedure in which a new aorta is created and connected to the right ventricle
  • A tube is also placed from either the aorta or right ventricle to the blood vessels that supply the lungs (pulmonary arteries)
  • This difficult procedure still may result in bluish skin because oxygenated and non-oxygenated blood still continue to mix in the heart
• The next surgical procedure, called the bi-directional Glenn procedure, is typically planned when the child is between 3-6 months of age. This procedure connects the major vein which carries deoxygenated blood from the top half of the body (superior vena cava) directly to the pulmonary arteries to become oxygenated
• A final surgery is typically performed when the child is anywhere between 18 months to 4 years of age and is called the Fontan procedure. This surgery connects the rest of the veins that carry deoxygenated blood from the body to the pulmonary arteries to be oxygenated by the lungs
• The right ventricle is now the pump for only the body, and not for the lungs, after the Fontan procedure. The child will now have normal blood oxygen level
• In some, follow-up surgeries may be necessary later in life to fix any uncontrollable complications from past surgeries
• Another option when heart defects are very complex, and surgery is difficult is a heart transplant. Individuals with Hypoplastic Left Heart Syndrome are eligible for a heart transplant

Regular follow up appointments after any treatment are recommended by healthcare professionals.

How can Hypoplastic Left Heart Syndrome be Prevented?

There are no known preventative measures presently available for Hypoplastic Left Heart Syndrome.

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

What is the Prognosis for Hypoplastic Left Heart Syndrome? (Outcomes/Resolutions)

The Prognosis for Hypoplastic Left Heart Syndrome without treatment is poor and the condition is usually fatal.

• Multi-staged surgical interventions can help result in much better outcomes; it is observed that the survival rate after just the first procedure (Norwood procedure) is above 75%
• Each case of Hypoplastic Left Heart Syndrome is different, and the outlook after surgery depends on the formation and function of the right ventricle
• Children may present lifelong complications following surgical correction(s) of the abnormality

Additional and Relevant Useful Information for Hypoplastic Left Heart Syndrome:

• Caring for a child with a congenital heart condition such as Hypoplastic Left Heart Syndrome can be difficult and counseling from the child’s cardiac specialist should be given to the parents
• It is important to monitor an infant with Hypoplastic Left Heart Syndrome regularly before and after surgeries, and to record health history and observations about the infant for healthcare specialists

It is important for parents to be aware of possible outcomes or future complications of the condition after surgery and parents should know which actions to take when certain symptoms may occur. Talking to and asking questions to a cardiac specialist can be very helpful to parents, helping them known and understand how to care for their child in the future