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Single Ventricle Physiology & Palliation
Children’s heart conditions can’t be prevented, but a lot can be done to improve and often completely repair their hearts at any age. Thanks to advanced technology and the pediatric heart experts at the Nemours Cardiac Center (based at Nemours/Alfred I. duPont Hospital for Children), most children born with a heart problem — even newborns only hours or days old — can be quickly diagnosed and treated right when it matters the most. At the Cardiac Center, we specialize in early detection and repair of congenital heart defects (also often called, “congenital heart disease”).
If your child’s been diagnosed with single ventricle physiology (sometimes called a “single ventricle defect” or “single ventricle anomaly”), we’re here to ease your concerns, answer your questions, and give your child the best possible chance for a healthy future.
The human heart usually has four chambers:
- two upper chambers (the atria, or when referring to one of them, “atrium”)
- two lower chambers (the ventricles)
The atria receive blood into the heart (the right atrium from the body, the left atrium from the lungs), while the ventricles pump blood out (the right ventricle to the lungs, the left ventricle to the body).
The normal circulatory system is arranged “in series,” which means that the blood flows from the body through the right heart, to the lungs, back to the left heart and out to the body again.
In contrast, the circulation in single ventricle heart disease is set up in “parallel” because only one of the lower pumping chambers is available to push blood out. So the blood exiting the heart from the single ventricle either gets directed to the lungs or the body. The amount of blood that goes to either the body or the lungs depends on several factors that affect how easily the blood flows. Because varying amounts of blood may be pumped to either the lungs or the body, it’s important that there is mixing of oxygenated (containing oxygen) and deoxygenated (containing very low oxygen). This mixing can occur within the heart through septal defects (holes in the heart) or between lung and body arteries outside the heart. With mixing, adequate amounts of oxygen can then be delivered by the circulatory system to other organs of the body such as the brain, liver, kidneys and muscles.
Single ventricle congenital heart defects cover a wide spectrum including the following:
- hypoplastic left heart syndrome
- tricuspid atresia
- unbalanced atrioventricular septal defect
- Ebstein’s anomaly of the tricuspid valve
In some of these cases, the available pumping chamber is a left ventricle (designed to pump to the body) and in other cases it’s a right ventricle (designed to pump to the lungs). There are even cases where there are two ventricles, but the structure of those ventricles and their relationship to the valves leading into and out of the heart results in only one chamber being able to pump forward.
The reason all of these different defects are combined into one category is that, regardless of the initial defect, all of them require a similar series of operations with nearly identical end results.
How Does the Heart Normally Work?
When your child has a congenital heart defect, there’s usually something wrong with the structure of the heart. In order to understand your child’s condition, it can help to know how the heart should work normally.
Learn More About Normal Cardiac Anatomy »
Nemours’ experts at KidsHealth.org also offer these helpful resources to help both you and your child understand how the heart works:
Single ventricle defects are diagnosed either during pregnancy by a fetal echocardiogram (“echo”) or shortly after birth with an echo. An echo is a completely safe and painless test that uses ultrasound (sound waves) to build a series of pictures of the heart.
When babies are born without being diagnosed, they may become very ill, but the exact symptoms will depend on the specific defect producing single ventricle physiology.
With single ventricle physiology, there are usually at least three operations performed. The goal of the series of surgeries (called “single ventricle palliation”) is to transform the heart and circulation from the abnormal circulation at birth to one where the heart:
- pumps the blood out to the body
- returns the blood to the lungs (without being pumped by the heart as it would be in a child with two normal ventricles)
- then returns the blood back to the heart
“Palliation” is the term used when a surgical procedure creates an alternative circulation, rather than repairing the heart and returning it to a “normal” circulation. Palliative procedures are usually performed when a complete repair isn’t possible, usually because certain structures of the heart are too small or completely absent.
The Three Stages of Single Ventricle Palliation Operations
The first operation varies, depending on the diagnosis. But the second and third surgeries are usually the same no matter which kind of heart defect a child might have.
The three operations work like this:
This stage depends on the underlying diagnosis, but is usually performed in newborns. The goal of the operation is to provide enough (but not too much) pulmonary blood flow.
Depending on the underlying diagnosis, there are three options:
- In children who have an obstruction to blood flow to the lungs, the first operation usually involves placing a tube (or “shunt”) from the aorta or another artery to the pulmonary artery. Without a shunt, the blood wouldn’t be able to reach the lungs to gather oxygen for delivery to the body. There are a variety of names for this shunt depending on its exact location, but the most common are a “central shunt” or a “modified Blalock-Taussig shunt.” The shunt is sized to allow the right amount of blood flow to the lungs.
- When children with single ventricle physiology have too much blood flow to the lungs, they may have a pulmonary band or bands placed. These are loops that are placed around the pulmonary artery to make it smaller. They create a narrowing that limits the amount of blood that can flow to the lungs. This is done so that (1) the lungs don’t get flooded with too much blood, and (2) the heart isn’t forced to pump more blood than necessary.
- In rare cases, the defect may not require any operation in newborns. Children who have a naturally controlled pulmonary blood flow may simply be allowed to grow until they’re old enough for the second operation.
In all cases, after the first operation, patients will have both deoxygenated (“blue”) blood from the body and oxygenated (“red”) blood from the lungs returning and mixing within the heart. This results in lower-than-normal oxygen saturations and may lead to a slight bluish color (this is called “cyanosis”) which is expected to get worse as the child grows and outgrows the shunt or band.
Part of our decision to proceed with the second operation is based on:
- how quickly the child outgrows the shunt or band from the first operation
- the changes in the delivery of oxygen to the body
Following whichever operation is required first in stage 1, the second operation is usually performed somewhere between 4 and 7 months of age. This procedure is called the “second stage operation” (or the “superior cava pulmonary connection”).
This operation can be one of two types:
- “hemi-Fontan” procedure
- “bidirectional Glenn” procedure
In both cases, the superior vena cava (the main blood vessel draining deoxygenated or “blue” blood from the upper body) is connected to the pulmonary artery. This results in blood draining from the upper body and going directly to the lungs without first passing through the heart. The importance of this procedure is that it relieves the single ventricle from having to pump too much blood. Before 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 because the lung is supplied with blood flow directly from the superior vena cava. But, because deoxygenated blood from the lower body continues to mix in the heart with the oxygen-rich blood from the lungs, children with either a hemi-Fontan or a bidirectional Glenn continue to have somewhat low oxygen levels.
The third stage is intended to correct the low oxygen levels and is usually performed somewhere between 16 months and 3 years of age. This is called the “Fontan” procedure (or a “total cavopulmonary connection”).
In this operation, blood draining the lower body through the inferior vena cava (the large vein bringing blood from the abdomen to the chest) is connected to the pulmonary artery. The result is that oxygen-rich blood (from the lungs) no longer mixes in the heart with oxygen-poor blood (from the body) because all of the blood from the body (carried in the vena cavae) is now directed into the pulmonary arteries (hence, the term “total cavopulmonary connection”). The heart now pumps blood out to the body. Then, as it returns to from the body, the blood flows passively (without being pumped by the heart) into the pulmonary arteries and the lungs. It then returns to the heart and is pumped out the body again.
In the period immediately after the operation, a small hole (called a “fenestration”) is usually left that allows a small amount of blood to bypass the lungs and return to the heart. This is done in order to help the heart through the operation itself. The fenestration is usually closed using a catheter at some point months or years later. Following the Fontan procedure, the oxygen levels in the body are nearly normal.
In addition to the series of three operations, other procedures may be required, depending on a child’s exact diagnosis. There are some differences in children who have only one ventricle. They can live normal lives in the long run.
But once children reach the Fontan procedure, they will have similar follow-up, challenges and potential complications. Most children with single ventricle physiology and palliation are on medications their whole lives. And although some children who had the Fontan operation will be able to exercise normally, many will have some limitation to their ability to be active and exercise.
If your child has single ventricle physiology, know that at the Nemours Cardiac Center we’re here to give your child the very best, most comprehensive and compassionate care. Our goal is to guide your family, from start to finish, through your child’s heart defect journey — and to help your child live the healthiest, most fulfilling life possible.
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