What is Tetralogy of Fallot?

One of the problems tetralogy of Fallot causes is a ventricular septal defect or VSD, a small hole in the septum, the wall between the lower chambers of the heart. This hole disrupts normal blood flow, allowing deoxygenated blood returning from the body to mix with oxygenated blood from the lungs. This reduces how much oxygenated blood returns to the body, which can significantly damage the heart over time.

The second issue babies with tetralogy of Fallot face is an overriding aorta. The aorta is the main artery leading out of the heart. Normally, it branches off from the left ventricle and carries oxygenated blood into the body. In tetralogy of Fallot, the aorta is directly above the VSD, slightly to the right of its normal position. This means that the aorta receives blood from both the right and left ventricles, a mix of oxygen-poor and oxygen-rich blood.

Another issue tetralogy of Fallot causes is pulmonary valve stenosis. The pulmonary valve lies between the right ventricle and the pulmonary artery, which carries oxygen-poor blood into the lungs. With pulmonary valve stenosis, this pathway narrows, restricting the amount of blood. Pulmonary valve stenosis can also affect the muscle beneath the valve, causing other blood flow problems.

Right ventricular hypertrophy is the fourth defect in tetralogy of Fallot. Because the heart has to work harder to move blood into the lungs due to the pulmonary valve stenosis, the right ventricle begins to thicken and stiffen, becoming increasingly weaker until it eventually fails.

The combination of defects in tetralogy of Fallot disrupts the entire process of blood exchange within the heart. Babies born with the condition face a higher risk of arrhythmias, endocarditis, and growth and developmental delays.

Signs and symptoms of tetralogy of Fallot include an abnormal heartbeat and cyanosis, a blue or purple tint to the nails, lips, and skin. Babies also experience periods where their oxygen levels drop suddenly, causing their skin to become even bluer. These "spells" first cause the baby to be increasingly fussy or irritable before becoming extremely sleepy or unresponsive. Older children with tetralogy of Fallot may also develop clubbing at the fingertips due to a chronic lack of oxygen.

Tetralogy of Fallot can be diagnosed before birth. If an ultrasound discovers the condition, a specialist may follow the pregnancy and develop a care plan for immediately after birth. Sometimes, doctors do not diagnose the condition until after the birth, either before the family leaves the hospital or at a follow-up appointment. Diagnosis involves a variety of tests, including pulse oximetry to monitor the oxygen content of the blood, an ECG to check the electrical activity in the heart, and an MRI to visualize the abnormalities.

The exact cause of tetralogy of Fallot is unknown but some factors increase the risk that a fetus will develop the condition. These include poor nutrition, alcoholism, or a viral illness during pregnancy, a parent who has tetralogy of Fallot, a mother older than 40, and DiGeorge or Down syndrome.

The only treatment for tetralogy of Fallot is surgery, which the doctor usually performs soon after the baby is born. The number of defects and issues makes the repair quite extensive. A cardiac surgeon widens or replaces the pulmonary valve to correct stenosis, expanding the passage between the right ventricle and the lungs. They also patch the VSD to close the hole between the lower chambers, preventing oxygen-poor and oxygen-rich blood from mixing.

A diagnosis of tetralogy of Fallot is stressful and scary for parents, but the surgery has a high success rate. Most children born with this extensive cardiac defect go on to lead healthy, normal lives. A pediatric cardiologist will follow the infant through childhood, and the individual will later transition to an adult cardiologist, typically at the age of 18. Problems can develop later in life, including arrhythmias and leaky valves, that may require medication or additional surgeries.