Hypoplastic Left Heart Syndrome

Heart with Hypoplastic Left Heart Syndrome

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Hypoplasia is defined as underdevelopment of a tissue or organ, usually due to a deficiency in the number of cells. Hypoplastic left heart syndrome is the underdevelopment of the left side of the heart, including the left atrium and ventricle, the mitral valve, the aortic valve, and the aorta.

In some cases an associated ASD allows blood returning from the lungs to flow through the opening in the septum from the left to the right atrium. The mixed blood enters the right ventricle and is then pumped into the pulmonary artery. The blood reaches the aorta through a patent ductus arteriosus, which is kept open by intravenous medication. This heart defect is fatal within the first days or months of life without treatment.

Treatment Options

Options for treatment include a series of three operations collectively known as the Norwood Procedure or heart transplantation. The goal of the Norwood Procedure is to direct deoxygenated blood directly to the lungs and utilize the functional right heart to pump oxygenated blood to the body.

 
Stage I Norwood Procedure

The first stage, performed in the first week of life, is known as the Stage I Norwood Procedure. The connection between the right ventricle and the branch pulmonary arteries is broken and the main pulmonary artery and the small aorta are connected and augmented to create a new, larger aorta. Next, a small tube (shunt) is placed between the aorta and the right branch pulmonary artery to allow for blood flow to the lungs.

Post-Modified Stage I Norwood Procedure

The modified Stage 1 Norwood Procedure connects the Pulmonary artery to the Right Ventricle using a shunt. The underdeveloped Aorta is reconstructed and enlarged.

The right ventricle is converted into a common systemic (to the body) ventricle. The oxygenated and de-oxygenated blood mix in the right atrium and right ventricle and is then dispersed out to the body, through the reconstructed aorta, and to the lungs through the RV to PA shunt and pulmonary artery.

The purpose of the modified Stage 1 Norwood Procedure is to allow blood to circulate in a controlled manner throughout the body, without obstruction.

 
Hemi-Fontan Procedure (Second Stage)

The Hemi-Fontan procedure is the second of three operations for children with hypoplastic left heart syndrome and other types of single ventricle physiology. This procedure is generally performed at 6 months of age. The Hemi-Fontan consists of anastomosis of the superior vena cava (SVC) to the right pulmonary artery, augmentation of the branch pulmonary arteries and patch closure of the communication between the superior vena cava and the right atrium.

After the Hemi-Fontan procedure, the blue blood returning from the upper body through the SVC is immediately diverted to the lungs, without passing through the heart. This blood becomes oxygenated in the lungs and returns to the left atrium. This red or oxygenated blood then passes through the atrial communication into the right atrium. The deoxygenated blood from the lower body enters the right atrium through the inferior vena cava (IVC); there it mixes with the oxygenated blood from lungs. The mixed blood then passes into the right ventricle and is pumped out into the reconstructed aorta to supply the body. The importance of this procedure is that it relieves the single ventricle of having to pump an excess volume of blood. Prior to this procedure, the ventricle is pumping both to the body and to the lungs. Following the Hemi-Fontan, the ventricle pumps only to the body, since the lung is supplied with blood flow directly from the superior vena cava.

 
Third and Final Stage

The third and final stage is performed at approximately 12 months of age. During this procedure, the deoxygenated blood of the lower half of the heart is directed to the lungs. This is done by channeling the blood of the inferior vena cava through the right atrium to the right branch pulmonary artery.


What is Normal Cardiac Anatomy?

When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.

 
Learn More About Normal Cardiac Anatomy

Heart with Normal Cardiac Anatomy

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When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.

The heart is composed of four chambers. The two upper chambers, known as atria, collect blood as it flows back to the heart. The two lower chambers, known as ventricles, pump blood with each heartbeat to the two main arteries (the pulmonary artery and the aorta). The septum is the wall that divides the heart into right and left sides. The atrial septum separates the right and left atria; likewise, the ventricular septum separates the two ventricles.

There are four valves that control the flow of blood through the heart. These flap-like structures allow blood to flow in only one direction. The tricuspid and mitral valves, also known as the atrioventricular valves, separate the upper and lower chambers of the heart. The aortic and pulmonary valves, also known as the arterial valves, separate the ventricles from the main arteries. Oxygen-depleted blood returns from the body and drains into the right atrium via the superior and inferior vena cavas. The blood in the right atrium then passes through the tricuspid valve and enters the right ventricle.

Next, the blood passes through the pulmonary valve, enters the pulmonary artery, and travels to the lungs where it is replenished with oxygen. The oxygen-rich blood returns to the heart via the pulmonary veins, draining into the left atrium. The blood in the left atrium passes through the bicuspid, or mitral, valve and enters the left ventricle.

Finally, the oxygen-rich blood flows through the aortic valve into the aorta and out to the rest of the body.

Patent Ductus Arteriosus (PDA)

The lungs are not used while a fetus is in the amniotic fluid because the baby gets oxygen directly from the mother's placenta. When a newborn breathes and begins to use the lungs, the DA is no longer needed and usually closes during the first 2 days after birth.

But when the DA fails to close, a condition called patent (meaning "open") ductus arteriosus (PDA) results, in which oxygen-rich blood from the aorta is allowed to mix with oxygen-poor blood in the pulmonary artery. As a result, too much blood flows into the lungs, which puts a strain on the heart and increases blood pressure in the pulmonary arteries.

Causes

The cause of PDA is not known, but genetics might play a role. PDA is more common in premature babies and affects twice as many girls as boys. It's also common among babies with neonatal respiratory distress syndrome, babies with genetic disorders (such as Down syndrome), and babies whose mothers had German measles (rubella) during pregnancy.

In the vast majority of babies with a PDA but an otherwise normal heart, the PDA will shrink and go away on its own in the first few days of life. Some PDAs that don't close then will close on their own by the time the child is a year old.

In premature infants, the PDA is more likely to stay open, particularly if the baby has lung disease. When this happens, treatment to close the PDA might be considered.

In infants born with additional heart defects that decrease blood flow from the heart to the lungs or decrease the flow of oxygen-rich blood to the body, the PDA could actually be beneficial and the doctor might prescribe medicine to keep the ductus arteriosus open.

Symptoms and Tests

Babies with a large PDA might experience symptoms such as:

  • a bounding (strong and forceful) pulse
  • fast breathing
  • poor feeding habits
  • shortness of breath
  • sweating while feeding
  • tiring very easily
  • poor growth

If a PDA is suspected, the doctor will use a stethoscope to listen for a heart murmur, which is often heard in babies with PDAs. Follow-up tests might include:

  • a chest X-ray
  • an EKG, a test that measures the heart's electrical activity and can show if the heart is enlarged
  • an echocardiogram, a test that uses sound waves to diagnose heart problems. These waves bounce off parts of the heart, creating a picture of the heart that is shown on a monitor. In babies with PDA, an echo shows how big the opening is and how well the heart is handling it.

Treatment

The three treatment options for PDA are medication, catheter-based procedures, and surgery. A doctor will close a PDA if the size of the opening is large enough that the lungs could become overloaded with blood, a condition that can lead to an enlarged heart.

A PDA also might be closed to reduce the risk of developing a heart infection known as endocarditis, which affects the tissue lining the heart and blood vessels. Endocarditis is serious and requires treatment with intravenous (IV) antibiotics.

Reviewed by: Gina Baffa, MD
Date reviewed: February 2012