Tetralogy of Fallot

Tetralogy of Fallot is characterized by four heart defects that cause insufficient blood to reach the lungs and oxygen-depleted blood to be sent to the body. This combination of anatomical defects results in cyanosis (blue skin, nails, toes and lips) and can eventually weaken the heart. The four abnormalities associated with tetralogy of Fallot are:

• Ventricular septal defect. This is a hole in the wall (septa) that separates the heart’s two lower chambers or ventricles. The opening permits deoxygenated blood from the right ventricle to mix with oxygen-rich blood from the left ventricle, lowering the oxygen in blood delivered to the body.
• Pulmonary stenosis. This is an abnormal narrowing of the heart valve that sits between the right ventricle and the pulmonary artery. In a heart that functions normally, oxygen-poor blood from the right ventricle travels through the pulmonary valve and pulmonary artery to the lungs, where it receives oxygen. With pulmonary stenosis, however, the valve is narrowed. This increases the heart’s workload and decreases the amount of blood that flows to the lungs.
• Right ventricular hypertrophy. Because of the heart’s increased workload, the muscle of the right ventricle starts to thicken. This can lead to heart failure.
• Overriding aorta. This defect occurs when the aorta is located over the ventricular septal defect, rather than its normal spot over the left ventricle. Poorly oxygenated blood is sent to the body rather than being routed into the pulmonary artery, where it would normally travel to the lungs to pick up oxygen.

While no specific cause has been found, this condition may result from a combination of genetic and environmental factors. Circumstances that increase the risk for tetralogy of Fallot in a baby include maternal age over 40 and exposure to rubella or other viruses during pregnancy. Diabetes, poor nutrition and excessive alcohol use during pregnancy are also linked to the condition.

Symptoms of Tetralogy of Fallot

Symptoms associated with tetralogy of Fallot typically occur by the time an infant is just a few weeks old, including:

• Cyanosis (skin that turns blue)
• Difficulty breathing and tiring during feeding
• Lethargy
• Fussiness
• Heart murmur (an unusual whooshing sound made by the heart)

Diagnosis of Tetralogy of Fallot

A diagnosis can be made by an echocardiogram, which is an ultrasound that shows the structural abnormalities associated with tetralogy of Fallot. Frequently, an EKG is also performed to evaluate the heart’s electrical activity, heart rate and rhythm.

Occasionally, patients with tetralogy of Fallot require more invasive techniques such as cardiac catheterization to help diagnose and plan for surgical repair. During a cardiac catheterization, a small diameter tube is inserted into the neck or groin and maneuvered through the heart and blood vessels under x-ray guidance. The tube is equipped to give important information about how the blood flows through the heart. It can also measure oxygen levels within the heart and blood vessels.