Hypoplastic Left Heart Syndrome (HLHS)

How Does Hypoplastic Left Heart Syndrome Affect the Body?

HLHS affects how the heart works and how blood moves through the body. Here’s how:

• Small Left Ventricle: The left side of the heart (which usually pumps oxygen-rich blood to the body) is too small or doesn’t work at all.
• Valve Problems: The valves that let blood flow in and out of the heart (the mitral and aortic valves) may be too small or completely blocked.
• Small Aorta: The main blood vessel that carries oxygen-rich blood from the heart to the body is also smaller than normal.
• The Right Side of the Heart Works Harder: Since the left side of the heart cannot do its job, the right side has to work harder to pump blood to the lungs and the rest of the body.

What Causes Hypoplastic Left Heart Syndrome?

The exact cause of HLHS isn’t fully understood, but certain factors increase the chance of it happening:

• Genetic Factors: Sometimes, HLHS is linked to genetic syndromes or a family history of heart problems.
• Family History: If a family member was born with a congenital heart defect, there’s a slightly higher chance that another child in the family could have HLHS.
• Maternal Health: If the mother has health conditions like diabetes or obesity, the risk for HLHS may be higher.
• Medications and Substance Exposure: Certain medications or drug exposure during pregnancy can increase the risk of heart defects.

What Are the Symptoms of Hypoplastic Left Heart Syndrome?

The signs of HLHS usually appear shortly after birth, especially as a special blood vessel called the ductus arteriosus (which helps blood flow in the womb) starts to close. Symptoms may include:

• Blue or Purple Skin, Lips, or Nails (Cyanosis) occur when the body doesn’t get enough oxygen-rich blood.
• Difficulty Breathing: Babies with HLHS may breathe very fast or struggle to breathe.
• Poor Feeding and Weight Gain: Babies may have trouble feeding and not gain weight properly.
• Sleepiness or Weakness: The baby may seem overly tired, sleepy, or hard to wake.
• Cool Hands and Feet: Poor blood flow can make the baby’s hands and feet feel cool.
• Weak or Hard-to-Feel Pulse: A doctor might notice the pulse in the baby's arms or legs is weak.
• Heart Murmur: A doctor may hear an unusual “whooshing” sound when listening to the heart, which is caused by abnormal blood flow.

How is Hypoplastic Left Heart Syndrome Diagnosed?

HLHS can sometimes be detected before birth or shortly after birth using the following methods:

During Pregnancy:

• Ultrasound: A routine pregnancy ultrasound may show that the heart is not developing normally.
• Foetal Echocardiogram: If a doctor suspects a heart problem, a specialised ultrasound called a foetal echocardiogram can give a detailed view of the baby’s heart.

After Birth:

• Physical Exam: The doctor may see signs like cyanosis, weak pulses, or rapid breathing.
• Echocardiogram: This heart ultrasound shows the structure and function of the baby’s heart, confirming the diagnosis.
• Pulse Oximetry: This test checks the oxygen levels in the baby’s blood and can detect low oxygen caused by HLHS.
• Chest X-ray: Shows the size and shape of the heart and lungs.

How is Hypoplastic Left Heart Syndrome Treated?

HLHS is a very serious condition, and treatment must start as soon as possible after birth. Treatment usually involves a series of surgeries or, in some cases, a heart transplant. Here are the main treatment options:

Medications (Right After Birth)

Prostaglandin E1: This medication keeps the ductus arteriosus (a natural opening in a baby’s heart) open so blood can keep flowing properly until surgery can be done.

Surgery (Staged Approach)

There are typically three surgeries done over some time:

• Stage 1: Norwood Procedure (Newborn)
• This surgery is done within the first week of life. It allows the right side of the heart to pump blood to the body. The goal is to create a new pathway for oxygen-rich blood to reach the body.
• Stage 2: Glenn Procedure (4-6 Months Old)
• This surgery reduces the workload on the heart by directly connecting the large vein (the superior vena cava) to the pulmonary arteries. This allows oxygen-poor blood to flow to the lungs without passing through the heart.
• Stage 3: Fontan Procedure (2-4 Years Old)
• This final surgery allows all the blood returning from the body to flow directly into the lungs, bypassing the heart completely.

Heart Transplant

If the staged surgeries aren’t possible or complications arise, a heart transplant may be considered. The child would need to receive a donor's heart.

What Happens if Hypoplastic Left Heart Syndrome is Left Untreated?

Without treatment, HLHS is life-threatening. Here’s what can happen:

• Oxygen Levels Drop: The baby’s body can’t get enough oxygen, causing cyanosis (blue skin, lips, and nails).
• Heart Failure: The right side of the heart works too hard and may fail.
• Shock and Organ Failure: As blood flow decreases, vital organs like the brain, liver, and kidneys can be affected.

How Can Parents Reduce the Risk of HLHS?

Since the exact cause of HLHS isn’t fully known, there’s no guaranteed way to prevent it. But parents can take some steps to lower the risk of congenital heart defects:

• Regular Prenatal Care: Attend all prenatal checkups. Early detection can prepare the care team to treat the baby right after birth.
• Prenatal Screening: Early ultrasounds and echocardiograms can identify HLHS so doctors can plan immediate care after delivery.
• Healthy Lifestyle: Avoid smoking, drinking alcohol, and using recreational drugs during pregnancy.
• Control Medical Conditions: If the mother has diabetes or another medical condition, managing it during pregnancy is important.
• Consult a Genetic Counselor: If there is a family history of heart defects, genetic counselling can help parents understand their risk.

Living with Hypoplastic Left Heart Syndrome

Children with HLHS will need lifelong heart care. Even after surgery, children may need to take medications or have regular checkups with a heart specialist. Some children may need more surgeries or procedures as they grow.

What Parents Can Do:

• Keep Up With Medical Appointments: Regular follow-ups with a paediatric cardiologist are essential.
• Encourage Normal Activities (When Possible): As your child grows, doctors will help you understand safe physical activities.
• Support Emotional Well-Being: Growing up with a heart condition can be challenging, so provide emotional support and encourage social activities.
• Watch for Changes: Look for signs like blue skin, tiredness, or breathing problems.