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
If Your Child Has a Heart Defect
About Congenital Heart Defects
It can be frightening to learn that your child has a congenital heart defect. But these are relatively common, affecting almost 1 in every 100 newborns in the United States. Advances in medical knowledge and diagnostic technologies can provide very detailed information regarding structural heart abnormalities.
Congenital (meaning present at birth) defects usually are treated with surgery, catheter procedures, and sometimes medication. A combined approach using both surgery and catheterization is most common. Thanks to advances in pediatric heart surgery and interventional catheterization, nearly every form of congenital heart disease can be treated with the expectation of a good outcome.
Cardiac surgery and cardiac catheterizations are now performed on younger children — in fact, it's common for them to be done during infancy or even the newborn period, which has many long-term advantages.
Although nothing can be guaranteed with 100% certainty, most kids with heart problems can enjoy happy and healthy futures.
What Causes Congenital Heart Defects?
The human heart begins to form as a single tubular structure at about the fourth week of pregnancy. By the eighth week, this tube will gradually increase in length, eventually twisting upon itself. A wall, or septum, grows to divide the upper (atrial) and lower (ventricular) chambers into left and right sides. Four valves made of tissue develop, which keep blood moving forward through the cardiac chambers, lungs, and body as the heart pumps.
Multiple genetic and environmental factors interact to alter the development of the heart during the early stages of a fetus' development (the first 8 to 9 weeks during pregnancy). Sometimes, the cause of a congenital heart defect is known. Certain environmental exposures during the first trimester of pregnancy may cause structural abnormalities (including anticonvulsant medications such as phenytoin, the dermatological medication isotretinoin, or lithium salts for manic-depressive illness).
Uncontrolled diabetes, alcohol or drug abuse, or exposure to industrial chemicals during pregnancy also can increase the risk of congenital heart malformations. Some chromosome abnormalities, in which there is an extra or missing chromosome (or part of a chromosome) are associated with congenital heart disease. But most of the time, the specific cause of congenital heart disease is unknown.
Over the past 25 years, advances in ultrasound imaging techniques have led to sophisticated tools such as fetal echocardiography, making it possible for many congenital heart malformations to be diagnosed as early as the 12th to 20th week of pregnancy. Such imaging has reassured many parents-to-be that their baby's heart is normal. For others, it has offered an opportunity to know long before the birth that there's a malformation. This gives the family and doctors the ability to make well-informed decisions about the best treatment options.
Heart Problems Before Birth
Because the placenta (and not the fetus' lungs) does the work of exchanging oxygen and carbon dioxide, it is possible for even severe developmental abnormalities of the heart to exist without causing difficulties for the fetus. Such abnormalities may become important only after circulation transitions to the newborn state after birth (when the umbilical cord is clamped at the time of delivery, the placenta is no longer involved in the baby's circulation).
The newborn becomes dependent upon the lungs and circulatory system for the oxygen and blood flow needed to survive outside of the womb. The right side of the heart receives oxygen-poor blood flowing back from the body and pumps it to the lungs, where the circulating blood picks up more oxygen. The left side of the heart receives oxygen-rich blood from the lungs and pumps it out to the body.
Signs and Symptoms
After birth, the first sign of congenital heart disease is often the presence of a heart murmur. A murmur in itself is not a disease, but simply a sound. As the heart pumps blood, it sometimes creates vibrations that are heard through the doctor's stethoscope as a noise, or murmur.
Not all heart murmurs are signs of abnormalities — in fact, heart murmurs usually don't indicate the presence of any heart problem. Sometimes, a doctor can determine with the stethoscope alone whether a particular murmur is a sign of heart disease. In other cases, additional tests — such as chest X-rays, electrocardiograms (EKGs), or echocardiograms — will help determine the exact nature of a murmur.
Although many children with minor forms of congenital heart disease may not require any treatment, some can have serious symptoms early on that will require medical or surgical treatment within the first year of life. One such symptom can be breathing difficulties from lung congestion. This is usually the result of excessive blood flow from the left side to the right side of the heart through abnormal connections between the two sides of the circulation, such as holes in the heart (as in ventricular septal defect, atrial septal defect, atrioventricular canal, and patent ductus arteriosus).
Or the congestion could be the result of obstructions to blood flow on the left side of the heart, resulting in a backup of blood in the blood vessels returning blood from the lungs (such as in aortic stenosis, coarctation of the aorta, and hypoplastic left heart syndrome). The shortness of breath in these babies may interfere with their ability to feed and may result in an inability to gain weight adequately. Such babies may require medical treatment or a procedure such as surgery or cardiac catheterization within the first weeks of life.
Other symptoms of congenital heart disease relate to an inadequate amount of oxygen carried within the blood. These infants usually appear to have blue skin, a condition called cyanosis. This can be due to an obstruction of blood flow to the lungs (such as in tricuspid atresia or pulmonary atresia) or due to a hole within the heart that allows oxygen-poor blood to flow from the right to the left side of the heart and out to the body (such as in total anomalous pulmonary venous return or Ebstein's anomaly). It can also be related to an abnormal positioning (transposition) of the arteries leaving the heart. In any of these cases, less red oxygenated blood comes from the lungs and more blue unoxygenated blood is carried to the body, causing the blue skin color.
Treatment for Congenital Heart Defects
Many heart abnormalities (including patent ductus arteriosus, ventricular septal defect, truncus arteriosus, atrioventricular septal defect, tetralogy of Fallot, and transposition of the great arteries) can be corrected with a single operation in early infancy.
More complex abnormalities (including hypoplastic left heart syndrome and tricuspid atresia) may require a series of two or three operations beginning in the newborn period and completed at about 3 years of age. With most complex abnormalities, the children spend the majority of their time in the care of their parents at home, with occasional visits to the pediatric cardiologist (a heart specialist) as well as to the child's primary care doctor.
Less invasive procedures done in the cardiac catheterization laboratory, rather than the operating room, may be used to treat some conditions. These include balloon angioplasty or valvuloplasty to relieve an obstruction of a blood vessel (such as in coarctation of the aorta) or a valve obstruction (such as in pulmonary or aortic stenosis). In these procedures, a pediatric cardiologist inserts a catheter, a thin plastic tube with a special balloon attached, into a blood vessel. The balloon is then inflated to stretch open the narrow area of the blood vessel or heart valve.
Another procedure, transcatheter device occlusion, might be used to close abnormal openings or holes within the heart or blood vessels (such as in patent ductus arteriosus, atrial septal defects, and ventricular septal defects) without requiring surgery.
Some abnormalities, such as small- or moderate-sized ventricular septal defects, may close or decrease in relative size as a child grows. While waiting for the hole to close, the child might have to take certain medications, which some kids also need to take after surgery.
Whether treated surgically or medically, your child will need to regularly visit a pediatric cardiologist. At first, these appointments may be fairly frequent (perhaps every month or two), but after treatment, they may be cut back, sometimes to just once a year. The cardiologist may use tools like X-rays, electrocardiograms, or echocardiograms to monitor the defect and the effects of treatment.
Kids with congenital heart disease are at risk for bacterial endocarditis, an infection of the tissue that lines the heart and blood vessels. This serious illness requires prolonged treatment with intravenous antibiotics in a hospital setting.
Children with types of congenital heart disease that cause cyanosis should receive antibiotics before procedures that could introduce bacteria into the bloodstream, including dental work or surgery in places in the body where bacteria tend to grow (such as the mouth or gastrointestinal tract). Antibiotics also might be recommended after heart surgery for kids who have artificial heart valves or have had endocarditis before.
Most children with heart problems, however, do not need premedication with antibiotics. The pediatric cardiologist will be familiar with the latest guidelines, and can make recommendations based on the specific cardiac diagnosis, as well as procedure in question.
Children with heart defects should take good care of their teeth by brushing and flossing properly, and having regular dental visits and cleanings. Your child should see a dentist as early as possible, and as often as the dentist recommends.
If You Suspect a Problem
Although sudden serious downturns during or after cardiac treatment aren't common, you should watch for certain signs that could signal a need for medical attention. If your child appears to be working harder than normal to breathe, call your doctor right away.
Other signs that warrant immediate medical attention include:
- a bluish tinge or color (cyanosis) to the skin around the mouth or on the lips and tongue
- an increased rate of breathing or difficulty breathing
- poor appetite or difficulty feeding (which may be associated with color change)
- sweating while feeding
- failure to thrive (failure to gain weight or weight loss)
- decreased energy or activity level
- prolonged or unexplained fever
Call the doctor immediately if your child has any of these symptoms.
Caring for Your Child
Parenting kids with heart defects includes learning about basics like feeding, giving medicines, and watching for signs of trouble, but it also involves encouraging kids to become involved in their own care.
Because most congenital heart defects are now treated during infancy, it's often necessary to explain to an older child what happened in the past. When your child is old enough to understand, explain why he or she has a surgical scar, needs to take medication, or has to visit the pediatric cardiologist. Describe the treatment in a way your child can understand and don't try to hide the details.
If kids believe they have a role in their care, they're likely to be more confident and positive. Your doctor may be able to suggest ways to discuss these issues.
Participation in some physical activities might be limited, but kids can still play and explore with friends. Always check with the cardiologist about which activities your child should or should not be doing. Certain competitive sports could be restricted, for example.
Although it's tempting for parents to be overly protective, sheltering kids can make them feel isolated and stigmatized — which might do more harm than a heart defect in the long run. So do everything you can to make sure your child leads as normal a life as possible.
Reviewed by: Steven B. Ritz, MD
Date reviewed: August 11, 2016