Hypoplastic Left Heart Syndrome

This is a rare heart disease that is present at birth and it is known as Hypoplastic left heart syndrome (HLHS). It is a congenital heart defect in which the left heart’s side does not develop completely and it is too small. As a result, the heart muscle cannot pump blood properly. Therefore, the right side of the heart pumps the blood to the lungs and the whole body.

Healthcare professionals usually recommend medicines and heart surgery for those who suffer from HLHS. Sometimes, they may recommend a heart transplant.

Symptoms

Commonly, symptoms in babies with HLHS appear soon after birth. Check below some of them:

  • Cold feet and hands
  • Weak pulse
  • Drowsiness or reduced activity compared to other babies
  • Loss of appetite
  • Fast breathing
  • Gray or blue skin, lips, or fingernails

If the child does not receive treatment it may lead to shock. Check below some shock symptoms:

Seek emergency care if you notice that your baby experiences any of the following symptoms. For example breathing problems, weak or rapid pulse, cool and clammy skin, and skin color changes.

Causes

This condition occurs in the womb during pregnancy when the baby’s heart develops. Experts do not fully understand the cause but seems an abnormal gene plays a role. In babies with HLHS, the left side of the heart does not grow enough to develop completely. As a result, the heart muscle cannot send enough blood to the body. Check below heart parts that are too small in children with HLHS:

  • The left ventricle (the lower left heart chamber)
  • The aorta (the primary body’s artery)
  • Aortic and mitral valves (the valves on the left heart’s side)

However, the right side of the heart often pumps blood to the lungs and the rest of the body after birth. Thus, the blood goes through an opening that connects the aorta with the pulmonary artery directly. This opening is a vessel called ductus arteriosus. Thereafter, oxygen-rich blood returns to the right side of the heart through a natural opening between the right heart chambers (this opening is usually called the foramen ovale). The ductus arteriosus usually closes within 2 days after birth and the right side of the heart has no way to pump blood to the body and this job is done by the left heart’s side. In any case, the left heart’s side cannot pump blood well because it is underdeveloped in babies with HLHS. That’s why physicians recommend some medicines to maintain connections opened until heart surgery.

The only risk factor for HLHS is that people with one child with this congenital heart defect have an increased risk of having another baby with the same health problem.

What are the Possible Complications of Hypoplastic Left Heart Syndrome?

Many babies with HLHS survive with proper treatment but they require multiple surgeries. Check below some HLHS complications:

  • Delayed growth and development
  • Edema (fluid buildup in the feet and legs, lungs, and abdominal area)
  • Arrhythmia (irregular heart rhythm)
  • Easily get tired
  • Brain and nervous system conditions

Unfortunately, there is no way to prevent this condition because doctors do not understand the exact cause. Discuss with a genetic counselor before pregnancy.

Diagnosis

First, doctors will examine and listen to the heart using a stethoscope. After that, they may ask you some questions about family history and symptoms. Physicians also may perform some additional tests to confirm the condition. These include:

  • Pregnancy ultrasound – This test uses sound waves to produce detailed images of different body structures and organs. Ultrasound should be done during the second trimester of pregnancy to determine whether the baby has HLHS or not.
  • Echocardiogram – This test may show how the blood flows through the heart after the baby is born.

Treatment

Newborns with HLHS require treatment immediately including multiple surgeries or a heart transplant. Doctors may additionally recommend some medicines to reduce symptoms before surgery.

When HLHS is found during pregnancy, your doctor may recommend giving birth at a hospital with a cardiac surgery center.

Medicines

To keep the ductus arteriosus open, doctors usually recommend Alprostadil. In normal circumstances, it closes within several days but in newborns with HLHS, this opening should not close until heart surgery.

Therapies

The following procedures are often recommended by doctors while waiting for the surgery along with medications. For example:

  • Breathing help – If your baby experiences trouble breathing, doctors may recommend a ventilator (a breathing machine).
  • Fluids through a vein
  • Feeding tube – Many babies with HLHS have problems with feeding and physicians may recommend a feeding tube.

Other Treatments

Approximately all babies with HLHS require multiple surgeries. For example:

  • Atrial septostomy – This treatment involves catheters (tubes) and a balloon that produce or widen an opening between the upper chambers of the heart. Therefore, it allows more blood flow between them. Doctors usually recommend this treatment option if the foramen ovale closes or is too small. However, babies born with a hole in the heart (atrial septal defect) do not need atrial septostomy.

In addition, there are other treatment options that help restore blood flow to the lungs and the body. These procedures are performed in 3 stages. For example:

Norwood Procedure

Commonly, this procedure is done within the first 14 days of life. However, there are different ways to perform this treatment.

During this procedure, surgeons will rebuild the aorta and connect it with the right lower chamber of the heart. Thereafter, they will add a small tube (shunt) that allows enough blood to flow to the lungs. Furthermore, there are two types of tubes that surgeons may use. The first type of tube links the body’s main artery to the lung arteries. The second type begins from the right lower heart chamber to the pulmonary arteries. As a result, Norwood’s procedure lets the heart’s lower chamber supply both the lungs and the body with blood.

In some cases, surgeons may perform a mixed (hybrid) procedure in which they place a stent in the ductus arteriosus to keep the opening between the aorta and pulmonary artery. After that, surgeons will place certain bands around the pulmonary arteries to reduce the blood flow and make an additional opening between the heart’s upper chambers.

Bidirectional Glenn Procedure

In most cases, this is the second surgery usually performed between 4 and 6 months of age. During this procedure, surgeons will remove the first shunt and connect it with the large vein that drains blood from the arms and head to the pulmonary artery. After that, the lungs will get blood from the vein (superior vena cava) instead of the shunt.

This procedure reduces the work of the lower heart chamber by letting it pump blood primarily to the aorta. Thus, the oxygen-poor blood will return from the body directly into the lungs. The Bidirectional Glenn procedure leads all blood that returns from the upper body to flow to the lungs while oxygen-rich blood goes to the aorta, which helps supply organs and tissues in the body.

Fontan Procedure

This is a specific surgery usually done in children between 3 and 4 years old. During the Fontan procedure, doctors will make an additional path from the lower legs to the pulmonary arteries. The blood vessel involved in this surgery is called the inferior vena cava.

After this procedure, there is a little mix of oxygen-rich and oxygen-poor blood in the heart, which helps the skin not appear blue or gray.

Heart Transplant

Approximately all children with hypoplastic left heart syndrome require a heart transplant. Moreover, those who have heart transplants need to administer medications for the rest of their lives to prevent rejection of the transplanted organ.

Frequently Asked Questions

How usually HLHS is treated?

All babies born with this congenital heart defect require multiple surgeries. These include the Norwood procedure, the Glenn procedure, and the Fontan procedure. Sometimes, doctors may recommend a heart transplant. For more details, discuss it with your healthcare professional.

What are the main symptoms of HLHS?

These include:

  • Weakness
  • Color skin changes
  • Poor feeding
  • Cold extremities
  • Shortness of breath
  • Fast heartbeats

If you notice that your child experiences any of the previous symptoms or any other HLHS symptoms, seek emergency care.

What are the potential complications of hypoplastic left heart syndrome?

People with HLHS may experience certain complications. For example:

  • Need for multiple surgeries
  • Feeding complications (including poor nutrition, dysphagia, necrotizing enterocolitis, and others)
  • Digestive and liver problems
  • Nervous system and brain conditions (such as developmental conditions, neurological impairment, strokes, and others)
  • Blood clots
  • Fluid buildup, especially in the lungs and abdomen
  • Heart diseases (such as arrhythmias, heart failure, and others)

If you are concerned about HLHS complications, discuss it with your healthcare provider. If you have additional questions, ask your physician.

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