Tetralogy of Fallot is a congenital heart defect involving four abnormalities: a hole between the ventricles, narrowing of the pathway from the right ventricle to the lungs, an overriding aorta, and thickening of the right ventricle. These defects disrupt normal blood flow and can reduce the amount of oxygen reaching the cells of the body. Symptoms may include breathlessness, fatigue, poor weight gain, dizziness, fainting and episodes of blue or grey skin, known as “tet spells”. Diagnosis may occur during pregnancy or after birth using echocardiography, ECG and other imaging tests. Treatment usually involves surgery. Temporary procedures may be performed to improve blood flow to the lungs, or the surgeon may opt for a complete repair, often during infancy. Lifelong cardiac follow-up care is required.
Tetralogy of Fallot is a rare heart defect that the patient is born with. It is a combination of four different heart defects that occur simultaneously:
Ventricular septal defect (VSD) – The patient has a hole between the two lower chambers of the heart (ventricles). The right ventricle normally pumps deoxygenated blood from the heart to the lungs, whereas the left ventricle pumps oxygenated blood from the heart to the rest of the body. In Tetralogy of Fallot, the VSD allows blood to pass between the ventricles. The amount of deoxygenated blood entering the circulation depends largely on the severity of the obstruction to blood flow from the right ventricle to the lungs.
Pulmonary stenosis and right ventricular outflow tract obstruction – The pathway that carries blood from the right ventricle to the lungs is narrowed or obstructed. This may involve the area below the pulmonary valve, the pulmonary valve itself or, in some cases, the pulmonary arteries. This restricts blood flow to the lungs and makes the right ventricle work harder to pump blood through the narrowed pathway.
Overriding aorta – Normally, the aorta carries oxygenated blood from the left ventricle to the rest of the body. In Tetralogy of Fallot, the aorta is positioned partly over the ventricular septal defect, allowing blood from both ventricles to enter the aorta. Depending on the severity of the obstruction to blood flow to the lungs, this can allow more deoxygenated blood to reach the rest of the body and reduce the oxygen supplied to the tissues.
Right ventricular hypertrophy – The muscular wall of the right ventricle thickens because the right ventricle has to pump harder against the obstruction in the pathway leading to the lungs.
All four conditions affect the structure of the heart, changing the way blood flows through the body and potentially reducing the oxygen supply. The condition may be diagnosed during pregnancy, while the baby is still in the uterus.
The patient’s symptoms depend on the extent to which blood flow from the heart to the lungs is disrupted. Patients may have symptoms like:
Sometimes babies suddenly develop deep blue or grey skin, lips and nails. These episodes may happen when they cry, feed or become upset. These episodes are called “tet spells” and involve a sudden reduction in blood flow to the lungs, causing a rapid drop in blood oxygen levels. Babies may also lose consciousness, become limp or, in severe cases, have seizures during a tet spell.
The condition starts during pregnancy, while the baby’s heart is forming. The exact cause is unknown, but researchers are studying the role of genetic and environmental factors.
Some babies with Tetralogy of Fallot have an underlying genetic or chromosomal condition. For example, Tetralogy of Fallot can occur in children with Down syndrome or 22q11.2 deletion syndrome. Having a parent or sibling with a congenital heart defect may also slightly increase the risk of congenital heart disease.
The baby’s risk of developing congenital heart defects may also increase if the mother has certain medical conditions, such as diabetes, or certain infections, such as rubella, during pregnancy. Alcohol and tobacco exposure during pregnancy have also been associated with an increased risk of congenital heart defects. However, in most cases of Tetralogy of Fallot, the exact cause cannot be identified.
Congenital heart defects like Tetralogy of Fallot may be diagnosed during pregnancy or after the baby is born. Screening can be done during pregnancy with a fetal ultrasound, followed by a fetal echocardiogram if a heart abnormality is suspected.
After birth, paediatric cardiologist may perform diagnostic tests including an ECG, pulse oximetry testing and an echocardiogram. A chest X-ray, cardiac MRI or cardiac catheterisation may also be recommended in selected cases to provide more information about the heart and blood vessels or to help with treatment planning.
Babies with Tetralogy of Fallot usually need surgical treatment. The paediatric cardiologist may opt for complete repair during infancy, or may initially choose a temporary procedure to improve blood flow to the lungs before complete repair. The type of treatment and how soon it is performed depends on the baby’s condition, anatomy, oxygen levels and the severity of the obstruction to blood flow to the lungs.
Temporary Repair – Some babies may need palliative treatment to improve blood flow to their lungs before they are ready for complete repair. The surgeon may insert a Blalock–Taussig–Thomas (BTT) shunt to provide an alternative pathway for blood flow to the lungs. In selected babies, particularly those who are very small or have other medical concerns, a stent may be placed in the ductus arteriosus or the right ventricular outflow tract to improve blood flow to the lungs. These approaches may be considered when complete repair is not immediately appropriate.
Complete Repair – Patients with Tetralogy of Fallot need surgery to repair the congenital defects in their heart. This is often performed during infancy, although the timing varies depending on the baby’s condition and the anatomy of the heart. The repair is a multistep process that addresses the major abnormalities. The surgeon will close the hole between the ventricular chambers and relieve the obstruction to blood flow from the right ventricle to the lungs. This may involve repairing or preserving the pulmonary valve, widening the right ventricular outflow tract and, when necessary, enlarging the pulmonary arteries.
Once surgical repair is completed, blood flow from the right ventricle to the lungs improves, reducing the workload on the heart. Oxygen supply to the body also improves.
The long-term survival rates for patients with Tetralogy of Fallot have improved steadily over the years, as cardiac care becomes more advanced. Follow-up surgery or other procedures may be required in some cases. Patients will need lifelong care, even after surgery to correct the defect. They will need routine heart check-ups, including imaging tests, to monitor the function of the heart and identify any complications that may develop over time.
Some patients may develop problems such as pulmonary valve disease, enlargement or reduced function of the right ventricle, abnormal heart rhythms or residual defects after repair. Regular follow-up allows these problems to be detected and treated when necessary.
Physical activity recommendations are individualised. Many patients can participate in regular physical activity after successful repair, while some may need restrictions depending on their heart function, heart rhythm and other findings. Paediatric cardiologist may recommend exercise testing to determine safe levels of activity.
Most patients with repaired Tetralogy of Fallot can lead active and fulfilling lives, although lifelong follow-up with a congenital heart specialist is important.
If your child has been diagnosed with a congenital heart condition like Tetralogy of Fallot, the expert paediatric cardiology team at Kauvery Hospital is here to help. With branches in Chennai, Hosur, Salem, Tirunelveli, and Trichy, we provide comprehensive care and long-term support for children and families.
Tetralogy of Fallot is a congenital heart defect made up of four abnormalities: a ventricular septal defect, narrowing of the pathway to the lungs, an overriding aorta and right ventricular hypertrophy.
Symptoms may include breathlessness, poor weight gain, poor appetite, tiredness, dizziness, fainting and a heart murmur. Some babies may also develop sudden blue or grey skin, lips or nails during tet spells.
A tet spell is an episode in which blood flow to the lungs suddenly decreases, causing a rapid drop in blood oxygen levels. It may occur when a baby cries, feeds or becomes upset and can sometimes lead to loss of consciousness or seizures.
Yes. Tetralogy of Fallot may be detected during a fetal ultrasound. If a heart abnormality is suspected, a fetal echocardiogram can provide more detailed information about the baby’s heart.
Treatment usually involves surgery. Depending on the baby’s condition, anatomy and oxygen levels, the team may perform complete repair during infancy or first use a temporary procedure to improve blood flow to the lungs.
Complete repair involves closing the ventricular septal defect and relieving the obstruction to blood flow from the right ventricle to the lungs. The procedure may also involve repairing or preserving the pulmonary valve, widening the outflow tract or enlarging the pulmonary arteries.
Yes. Even after successful repair, lifelong cardiac follow-up is important. Regular check-ups and imaging can help monitor heart function and identify problems such as pulmonary valve disease, abnormal heart rhythms or changes in the right ventricle.
Many patients can participate in regular physical activity after successful repair, but recommendations depend on heart function, heart rhythm and other findings. A paediatric cardiologist may recommend exercise testing to determine appropriate activity levels.
Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai (Alwarpet, Radial Road & Vadapalani), Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and paediatric trauma care.
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