Tetralogy of Fallot is made up of the following four defects of the heart and its blood vessels:

1. A hole in the wall between the two lower chambers―or ventricles―of the heart. This condition also is called a ventricular septal defect.
2. A narrowing of the pulmonary valve and main pulmonary artery. This condition also is called pulmonary stenosis.
3. The aortic valve, which opens to the aorta, is enlarged and seems to open from both ventricles, rather than from the left ventricle only, as in a normal heart. In this defect, the aortic valve sits directly on top of the ventricular septal defect.
4. The muscular wall of the lower right chamber of the heart (right ventricle) is thicker than normal. This also is called ventricular hypertrophy.

Because a baby with tetralogy of Fallot may need surgery or other procedures soon after birth, this birth defect is considered a critical congenital heart defect. Congenital means present at birth.

This heart defect can cause oxygen in the blood that flows to the rest of the body to be reduced. Infants with tetralogy of Fallot can have a bluish-looking skin color―called cyanosis―because their blood doesn’t carry enough oxygen. At birth, infants might not have blue-looking skin, but later might develop sudden episodes of bluish skin during crying or feeding. These episodes are called tet spells.

Infants with tetralogy of Fallot or other conditions causing cyanosis can have problems including:

• A higher risk of getting an infection of the layers of the heart, called endocarditis.
• A higher risk of having irregular heart rhythms, called arrhythmia.
• Dizziness, fainting, or seizures, because of the low oxygen levels in their blood.
• Delayed growth and development.

Tetralogy of Fallot is a complex congenital heart defect characterized by a large ventricular septal defect (hole between the right and left ventricles), pulmonary stenosis (narrowing of the valve and artery that connect the heart with the lungs), an overriding aorta (the aorta - the artery that carries oxygen-rich blood to the body - is shifted over the right ventricle and ventricular septal defect, instead of coming out only from the left ventricle), and right ventricular hypertrophy (the muscle of the right ventricle is thicker than usual). Tetralogy of Fallot causes low oxygen levels in the blood, which can lead to cyanosis (a bluish-purple color to the skin). The cause of this condition is unknown. Treatment involves surgery to repair the heart defects. Sometimes more than one surgery is needed.

The heart is an organ, about the size of a fist. It is made of muscle and pumps blood through the body. Blood is carried through the body in blood vessels, or tubes, called arteries and veins. The process of moving blood through the body is called circulation. Together, the heart and vessels make up the cardiovascular system.

Structure of the Heart

The heart has four chambers (two atria and two ventricles). There is a wall (septum) between the two atria and another wall between the two ventricles. Arteries and veins go into and out of the heart. Arteries carry blood away from the heart and veins carry blood to the heart. The flow of blood through the vessels and chambers of the heart is controlled by valves.

Blood Flow Through the Heart

(Abbreviations refer to labels in the illustration)

The heart pumps blood to all parts of the body. Blood provides oxygen and nutrients to the body and removes carbon dioxide and wastes. As blood travels through the body, oxygen is used up, and the blood becomes oxygen poor.

1. Oxygen-poor blood returns from the body to the heart through the superior vena cava (SVC) and inferior vena cava (IVC), the two main veins that bring blood back to the heart.
2. The oxygen-poor blood enters the right atrium (RA), or the right upper chamber of the heart.
3. From there, the blood flows through the tricuspid valve (TV) into the right ventricle (RV), or the right lower chamber of the heart.
4. The right ventricle (RV) pumps oxygen-poor blood through the pulmonary valve (PV) into the main pulmonary artery (MPA).
5. From there, the blood flows through the right and left pulmonary arteries into the lungs.
6. In the lungs, oxygen is put into the blood and carbon dioxide is taken out of the blood during the process of breathing. After the blood gets oxygen in the lungs, it is called oxygen-rich blood.
7. Oxygen-rich blood flows from the lungs back into the left atrium (LA), or the left upper chamber of the heart, through four pulmonary veins.
8. Oxygen-rich blood then flows through the mitral valve (MV) into the left ventricle (LV), or the left lower chamber.
9. The left ventricle (LV) pumps the oxygen-rich blood through the aortic valve (AoV) into the aorta (Ao), the main artery that takes oxygen-rich blood out to the rest of the body.

The Centers for Disease Control and Prevention (CDC) estimates that each year about 1,660 babies in the United States are born with tetralogy of Fallot. In other words, about 1 in every 2518 babies born in the United States each year are born with tetratology of Fallot.

The causes of heart defects (such as tetralogy of Fallot) among most babies are unknown. Some babies have heart defects because of changes in their genes or chromosomes. Heart defects such as tetralogy of Fallot also are thought to be caused by a combination of genes and other risk factors, such as the things the mother or fetus come in contact with in the environment or what the mother eats or drinks or the medicines she uses.

Tetralogy of Fallot may be diagnosed during pregnancy or soon after a baby is born.

During Pregnancy

During pregnancy, there are screening tests (also called prenatal tests) to check for birth defects and other conditions. Tetralogy of Fallot might be seen during an ultrasound (which creates pictures of the body). Some findings from the ultrasound may make the health care provider suspect a baby may have tetralogy of Fallot. If so, the health care provider can request a fetal echocardiogram to confirm the diagnosis. A fetal echocardiogram is an ultrasound of the heart of the fetus. This test can show problems with the structure of the heart and how the heart is working with this defect.

After a Baby Is Born

Tetralogy of Fallot usually is diagnosed after a baby is born, often after the infant has an episode of turning blue during crying or feeding (a tet spell). Some findings on a physical exam may make the health care provider think a baby may have tetralogy of Fallot, including bluish-looking skin or a heart murmur (a “whooshing” sound caused by blood not flowing properly through the heart). However, it is not uncommon for a heart murmur to be absent right at birth.

The health care provider can request one or more tests to confirm the diagnosis. The most common test is an echocardiogram. An echocardiogram is an ultrasound of the heart that can show problems with the structure of the heart and how the heart is working (or not) with this defect. Echocardiography also is useful for helping the doctor follow the child’s health over time.

Tetralogy of Fallot is a critical congenital heart defect (critical CHD) that may be detected with newborn screening using pulse oximetry (also known as pulse ox). Pulse oximetry is a simple bedside test to estimate the amount of oxygen in a baby’s blood. Low levels of oxygen in the blood can be a sign of a critical CHD. Newborn screening using pulse oximetry can identify some infants with a critical CHD, like tetralogy of Fallot, before they show any symptoms.

Tetralogy of Fallot can be treated by surgery soon after the baby is born. During surgery, doctors widen or replace the pulmonary valve and enlarge the passage to the pulmonary artery. They also will place a patch over the ventricular septal defect to close the hole between the two lower chambers of the heart. These actions will improve blood flow to the lungs and the rest of the body.

Most infants will live active, healthy lives after surgery. However, they will need regular follow-up visits with a cardiologist (a heart doctor) to monitor their progress and check for other health conditions that might develop as they get older. As adults, they may need more surgery or medical care for other possible problems.

sha was born with a critical congenital heart defect (critical CHD), during a time when open heart surgeries in India were unheard of. Read her story below of how she exceeded all expectation for survival and how she is now one of the pioneering adults living with a critical CHD.

Here is my incredible journey as a congenital heart patient. I was born with four defects in the heart called tetralogy of Fallot, commonly known as “blue baby”. In the 1960s in India, open heart surgeries were unheard of. Uncorrected, this condition rarely survives into adulthood. At age 4, I had a procedure to help my blood bypass the problems in my heart, which helped me attend school. Trying my best to be “normal” despite a long “do-not-do” list, I completed high school. I had a growth spurt at age 15, and my student life came crashing down, as daily school attendance became a challenge. In 1976, I was given a 5% chance of survival for an open-heart surgery. The decision was momentous both to me and my family. The 8-hour surgery involved not only correcting the defects, but also fixing what had been done in my previous procedure. The result of the surgery was unknown for about 72 hours, but I pulled through with only a scar infection as a complication. A three month stay in the hospital was followed by a year of a salt-free diet and no school.

Having survived the open-heart surgery (called total correction), I became a medical example. My spirit demanded an unusual education. With the doctor’s permission, I opted to become a software engineer, and took up a career in information technology. I met a man who was brave enough to take me on for a spouse, and we moved to Scotland where I began a Master’s program. Thirteen years after the open-heart surgery, a new murmur led to the discovery of the results of the initial procedure coming undone. I was shuttled to Glasgow to a pediatric surgical center to fix it.

In 1992, we moved to the US and in 1997, I had a daughter – a 32 week preemie. Motherhood and pregnancy took a toll and by 2002, I began to feel breathless and exhausted. My pulmonary valve needed to be replaced. Again, it was yet another pediatric hospital and pediatric heart surgeon who fixed me. This time the survival rate given was 99% and only a week’s hospital stay!

I am one of the first groups of adults alive with this congenital heart defect. We form a new population whose healthcare needs have not yet been studied and whose prognosis and life-expectancy are still unknown. Recently, I experienced heart palpitations requiring medication to slow my heart. A new unexpected defect in the left side of the heart has also come to light, making me a “rare” case. Patients living into adulthood and their doctors now face the unknown. Stepping into the sixth decade of life, I realized that my heart will never be totally corrected. Hence, I will need life-long monitoring at a specialized health clinic. My advice to others like me is to contact specialized clinics and face the unknown together with the doctors. Public health has a very important role in helping such patients with much needed research.