The four components that make up the "tetralogy" include:
- a ventricular septal defect (VSD);
- pulmonary stenosis (subvalvar, valvar and/or supravalvar);
- an overriding aorta; and
- right ventricular hypertrophy.
The primary problem is the malalignment VSD, in which the infundibular or conal septum is malaligned anteriorly, thereby blocking the right ventricular outflow tract. The conal septum pulls the aorta anteriorly with it, into a position overriding the ventricular septum. The right ventricular hypertrophy occurs secondary to high pressure in the right ventricle (RV), created by the pulmonary stenosis and the large VSD. In the extreme situation, the right ventricular outflow tract is completely blocked off, in which case you have tetralogy of Fallot with pulmonary atresia.
The physiology is variable despite similar anatomy. The degree of RV outflow tract obstruction strongly influences the degree of cyanosis. With increasing degrees of obstruction, more and more of the desaturated (blue) blood is forced across the VSD and out into the aorta (a right to left shunt), thus never reaching the lungs to become oxygenated. On the other hand, if there is only mild RV outflow tract obstruction, there may be less resistance to blood flowing out the pulmonary artery than flowing to the systemic circulation. In this situation, excess blood tends to flow from the left ventricle to the right ventricle; i.e. a net left to right shunt. These patients are acyanotic ("pink Tetralogy of Fallot") and may actually develop congestive heart failure.
A patent ductus arteriosus (PDA) can play a very important role by providing an alternate pathway for blood to reach the lungs, allowing adequate pulmonary blood flow even in the face of very severe RV outflow obstruction. The flow across the PDA goes from left (the aorta) to right (the pulmonary artery) in this setting.
Children with tetralogy of Fallot are at risk of having hypercyanotic spells or "Tet spells". Spasm of the infundibular region (below the pulmonary valve) and/or a sudden increase in pulmonary vascular resistance produces a sudden decrease in the amount of blood getting to the lungs. Concomitantly, more blood is shunted from right to left and exits the aorta as desaturated blood. The resultant hypoxemia further increases the pulmonary vascular resistance and a downward spiral begins with the rapid development of acidosis. Older children learn to squat in order to prevent or alleviate a spell. It is believed that the squatting kinks the large arteries in the lower extremities, thus increasing the systemic vascular resistance and forcing more blood across the pulmonary outflow tract.
Surgical Management of Tetralogy of Fallot (TOF)
Definitive treatment of tetralogy of Fallot consists of surgical correction. Timing of surgery remains controversial but most agree that the presence of severe cyanosis or hypercyanotic spells necessitates surgical intervention. Complete repair consists of closing the ventricular septal defect with a patch and enlarging the right ventricular outflow tract. The latter usually requires incision across the pulmonary valve annulus and placement of a patch of synthetic material to widen the outflow tract at all levels of obstruction.
When surgical intervention is necessary in a patient who is not a good candidate for complete repair (i.e., very small patient size, tiny pulmonary arteries or an anomalous coronary artery course), a palliative procedure is performed. Palliation consists of placement of a shunt from the aorta to the pulmonary artery to increase pulmonary blood flow. The most commonly performed shunt today is the modified Blalock-Taussig shunt, in which a tube of Gore-Tex is placed between the subclavian artery and the 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.
Heart With 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.
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.
From Nemours' KidsHealth
- Cardiac Catheterization
- ECG (Electrocardiogram)
- If Your Child Has a Heart Defect
- Atrial Septal Defect
- When Your Child Needs a Heart Transplant
- Heart Murmurs
- Patent Ductus Arteriosus (PDA)
- Coarctation of the Aorta
- Congenital Heart Defects
- Ventricular Septal Defect
- Tetralogy of Fallot
- A to Z: Atrial Flutter
- A to Z: Hypoplastic Left Heart Syndrome
- A to Z: Patent Ductus Arteriosus (PDA)
- A to Z: Tetralogy of Fallot
- Heart and Circulatory System
- Congenital Heart Defects Special Needs Factsheet
Trusted External Resources
When Your Child Needs a Heart Transplant
If your child needs a heart transplant, you're probably feeling lots of emotions all at once — including anger, sadness, worry, and frustration. These feelings can become overwhelming, especially when your child is waiting for a new heart.
Fortunately, many kids who undergo heart transplants go on to live normal, healthy lives once they recover from surgery. In the long term, they need to take medicines to help prevent complications and have regular checkups to check heart function.
What Are Heart Transplants?
A heart transplant is a surgery in which doctors remove a person's sick heart and replace it with a healthy donor heart.
Transplants in children are done when a child's heart does not work properly and he or she won't survive without a new one. Doctors sometimes refer to this condition as heart failure, or end-stage pediatric heart disease. They usually try to treat heart failure with medicine, surgery, or other procedures before recommending a heart transplant.
Why Do Kids Need Heart Transplants?
A child's heart might not work right for many reasons. Sometimes, babies are born with heart defects (malformations) that cause their hearts to fail. These defects are the main cause of heart transplants in babies.
Certain forms of heart disease, such as cardiomyopathy, also can cause heart failure. Cardiomyopathy happens when the heart muscle does not function well. As a result, the heart cannot pump enough blood to the body. Cardiomyopathy is the main reason that children and teenagers need heart transplants.
Some other (less common) reasons that children might need heart transplants include myocarditis, an inflammation of the heart muscle, and abnormal heart rhythms, known as arrhythmias or dysrhythmias.
Transplanted hearts come from organ donors — adults and children who have agreed (or their guardians have agreed) to donate their organs in the event of an untimely death. They choose to donate the organs because they want to help someone else who is sick.
If your child needs a heart transplant, your doctor will refer you to a transplant center, where you'll meet the members of the transplant team. The team members probably will include surgeons, cardiologists (heart doctors), a transplant coordinator, nurses, nutritionists, psychologists, social workers, and other health care professionals.
What Tests Are Done?
The transplant team will evaluate your child to determine whether a transplant will be beneficial and whether your child is a good candidate for a transplant. The evaluation will include a medical history, a physical examination, and some tests, such as blood tests to determine blood type.
The team probably will perform several other diagnostic tests, which may include:
- an echocardiogram, a test in which sound waves are used to produce an image of the heart
- an electrocardiogram (also known as an ECG or EKG), a test that records the electrical activity of the heart and can help find arrhythmias and heart muscle damage
- cardiac catheterization, a procedure in which a thin, plastic tube called a catheter is inserted into a blood vessel and then threaded through to the heart in order to get an inside glimpse at the heart and its chambers
If the doctors want to examine the heart more closely, they will do a biopsy, removing a tiny piece of tissue from the heart to examine under a microscope.
The heart transplant evaluation lets the team learn as much about your child as possible. But it's also a time for you and your child to learn about what will happen before, during, and after the transplant. The transplant team is there to provide information and support, so be sure to ask them questions if you don't understand something.
What Happens Before Heart Transplant Surgery?
If the transplant team decides that a heart transplant is the right treatment, your child will be placed on an organ waiting list. This list has the names of all of the people who are waiting for hearts or other organs.
A group called the United Network for Organ Sharing (UNOS) oversees this list and is in charge of fairly determining who receives the donated organs. Organs are assigned based on how sick a person is and how quickly he or she needs a new organ.
Organs assignments also are based on which person on the waiting list is the best match for the organ donated. That means that the organ is the right size for the person's body and the donor has the same blood type as the recipient.
Your child might have to wait to find a heart that is a good match. Unfortunately, no one knows how long that wait will be. It could be just a few days or it could be years.
Waiting can be difficult, so consider seeking support from parents whose children have undergone or are awaiting transplants. Many communities have support groups or you can ask your doctor or the hospital social worker for recommendations, or search online.
What Happens During Heart Transplant Surgery?
When a suitable heart becomes available, your family will be notified by phone or pager and you will need to go to the hospital for the surgery right away. Because this could happen at any time, you should always be prepared.
When you get to the hospital, the transplant team will prepare your child for surgery. They may run a few tests to ensure that the new heart is a good match. Once the team decides that everything is OK, your child will be moved to an operating room.
In the operating room, your child will be given anesthesia to sleep through the surgery and won't feel anything. The surgeons will make an incision in the chest and remove the sick heart. They will connect the new heart by sewing its blood vessels to the blood vessels in your child's body. The new heart will then be placed in the chest. So that doctors can monitor heart function, the incision might not be sealed immediately.
Most heart transplant surgeries last between 4 and 6 hours. Someone on the transplant team will keep you informed about how the procedure is going while you wait.
What Happens After Heart Transplant Surgery?
Right after the surgery, your child will be moved to the cardiac intensive care unit (CICU). You will be able to visit your child in the CICU for brief periods. Your child will receive sedation and medicine for pain, and will remain asleep on the ventilator with a breathing tube in place until the doctors determine that the new heart is working well. This may take a few days.
The length of time your child will spend in the CICU will depend on his or her condition. Generally, the stay is 7 to 10 days. When ready, your child will be transferred to the general cardiac ward. The transplant team will continue to care for and closely monitor your child.
Most children stay in the hospital at least 3 to 4 weeks after surgery. During this time, kids and their families learn how to care for the new heart. Be sure you understand all of the doctors' instructions because your child will need to follow them carefully.
When the transplant team agrees that your child is ready, he or she will be discharged from the hospital. In the weeks that follow, though, your child will return to the hospital many times so that the doctors can continue to make sure that everything is going well.
What Problems Can Happen?
One of the most common problems after transplant surgery is rejection. Rejection is the body's normal reaction to something foreign. Usually, this reaction is beneficial. For example, it's the way the body defends itself against harmful germs.
In the case of a heart transplant, rejection means that the body doesn't recognize the new heart and doesn't know that it is helpful. As a result, the immune system tries to attack it. Medicines (called immunosuppressants) help to control this reaction. In a sense, they trick the body into accepting the new organ.
Although the risk of rejection is greatest in the first few weeks after transplant surgery, the body never completely accepts the new heart and so anti-rejection medications must be taken for life. The transplant team will decide which medicines are best for your child and these must be taken exactly as instructed.
Anti-rejection medications can cause some unwanted side effects, such as fever, headache, nausea, tiredness, and irritability. Be sure to report these and any other reactions to your doctor. Unfortunately, these medicines also leave your child vulnerable to certain infections. This risk is greatest right after surgery, and other medicines will be given to help reduce the risk. When possible, your child should avoid people who are sick to lessen the chances of getting an infection.
Usually, the amount of immunosuppressants taken is gradually reduced as the body gets used to the new organ and the risk of rejection decreases. In rare cases, the body refuses to accept the new organ and another heart transplant is necessary.
Many kids who have heart transplants live normal, healthy lives once they recover from surgery. Some feel better than they ever have before.
It's very important for you and your child to do everything possible to keep the new heart healthy. Make sure that your child takes all medicines as directed, and encourage him or her to get plenty of rest, exercise regularly, and eat well.
Also, watch your child for signs of infection and rejection, including fever, tiredness, difficulty breathing, vomiting, weight gain, and poor appetite. Immediately call your doctor if these or any other problems happen.
Your child will have regular checkups so doctors can watch for complications. At first, these visits will happen often (perhaps weekly). Over time, they'll become less frequent and eventually might be needed only once or twice a year.
Reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: August 01, 2017