Single Ventricle Surgery

The heart has two sides: a left side and a right side. Within these sides lie the chambers of the heart – there are two pumping chambers (the ventricles) and two collecting chambers.

In a normally-developed heart, the oxygen-poor (blue) blood returns to the right atrium from the body, enters the right ventricle, then is pumped through the pulmonary artery into the lungs where it receives oxygen. The oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle and is then pumped out to the body through the aorta.

For children with single ventricle defects, one of the ventricles has not developed properly or the inside arrangement of the two ventricles is too complicated to be separated into two.

The red blood will then mix with the blue blood, causing cyanosis or blueness, because the body receives less oxygenated blood. In order to thrive, babies born with single ventricle defects will need surgical intervention.

There are six types of single ventricle defects:

1. Hypoplastic left heart syndrome (HLHS): HLHS is a combination of several abnormalities of the heart and great blood vessels. Most structures on the left side of the heart are small and underdeveloped with this condition.
2. Tricuspid atresia: In tricuspid atresia, the tricuspid valve, normally located between the right atrium and the right ventricle, does not develop properly during pregnancy and remains completely obstructed.
3. Double outlet right ventricle: The pulmonary artery and aorta come out of the right ventricle. Sometimes the left ventricle remains small or it’s impossible to channel the blood from the left ventricle into the aorta.
4. Double inlet left ventricle: The two collecting chambers connect to the left ventricle resulting in the right ventricle being underdeveloped.
5. Unbalanced atrioventricular septal defect (AVSD): There is a large opening between the collecting and pumping chambers of the heart with abnormal valves. One of the pumping chambers remains smaller than the other.
6. Pulmonary atresia and intact ventricular septum: The exit of the right ventricle is obstructed and it remains very muscular and small.

It is generally unknown what causes single ventricle defects. In some cases it may have a genetic link, in others, it may occur randomly.

These congenital heart defects are rare, occurring in about five out of every 100,000 live births.

Single ventricle defects can be diagnosed while your baby is still in utero. These issues are not always caught in utero, though. Regardless of when diagnosis occurs, in most cases your baby will have to undergo surgery immediately after being born or within the first few days of life to correct the single ventricle defect.

The Fontan procedure is the last in a series of operations that tries to establish a near-normal circulation of blood. In the Fontan procedure, the veins draining the blood from the body are connected directly to the lung arteries, thereby bypassing the heart.

Stage 1: The first staged surgery is specific to your child’s anatomy. Your child may undergo a Norwood operation, a hybrid procedure, or a shunt only, such as a Blalock-Thomas-Taussig (BTT) shunt  

The Norwood procedure is an operation that can either occur within the first few days of birth (this is known as the primary Norwood) or within 3-4 weeks after birth (delayed Norwood). Depending on the type of single ventricle heart defect, different surgical approaches may be used. The purpose of this operation is to provide unobstructed blood flow to the body, so the surgeon must create a “neoaorta” which directs blood from the right ventricle out to the body. We must also provide a source of blood flow to your child’s lungs, and this is done through a shunt such as the BTT or Sano shunt. This is a temporary circulation, used until your child is old enough for the second surgical reconstruction, the Glenn procedure. 

Once your child is ready for discharge from the hospital, they will be enrolled in the Single Ventricle Home Monitoring Program. A dedicated nurse practitioner will monitor your child’s progress at home until they receive their Glenn procedure.

Stage 2: Glenn Procedure

The Glenn procedure is an open-heart surgery that typically takes place when your child is between 3 to 6 months of age. The surgeons will connect the superior vena cava, a large vein that carries blue blood from the upper half of the body into the heart, directly to the pulmonary artery. This will enable blue blood from the upper body to flow directly to the lungs, without passing through the heart. If your child had a BTT or Sano shunt, it will be removed since it is no longer needed.

Stage 3: Fontan Procedure

The Fontan procedure can be scheduled any time between 2 and 4 years of age, depending on what your child needs. During this surgery, the inferior vena cava, a large vein that carries blue blood from the lower half of the body into the heart, is attached directly to the pulmonary artery. After the Fontan operation, all of the blue blood will go directly to the lungs without passing through the heart. This takes away a significant amount of work for the single pumping chamber. Given all the advances in surgical care, children born with a single ventricle defect who have completed the Fontan procedure are now living well into adulthood.

Your physician will discuss risks with you and your family in greater detail. Potential risks of the Fontan procedure may include:

• Liver dysfunction
• Kidney issues
• Pregnancy complications, including blood clots and arrhythmia
• Some patients may need additional catheterization procedures, pacemakers or other surgeries over time.

Yes, long-term follow-up care is needed for children who have the Fontan procedure. Your child would continue to see a pediatric cardiologist throughout childhood and adolescence, and would transition to adult care at the end of adolescence. Your cardiologist will monitor your child’s heart and the Fontan procedure itself, as well as liver and kidney function.