Tetralogy of Fallot is a congenital defect which results from abnormal deviation of a part of the intraventricular septum, resulting in a large ventricular septal defect and abnormalities of the pulmonary artery. The pulmonary artery normally arises from the right ventricle and supplies de-oxygenated blood to the lungs.
The abnormalities of the pulmonary artery include pulmonary stenosis (narrowing of the pulmonary valve and artery), pulmonary atresia (no blood flow through a very small pulmonary artery) or absent pulmonary valve (causing forward and backward blood flow in a severely dilated pulmonary artery.
Newborns with tetralogy of Fallot usually present with a heart murmur, which is due to the abnormal pulmonary artery. Sometimes they can also have lower levels of oxygen because blood flow is limited to the lungs from the narrow pulmonary artery. This is more common when they cry.
What causes it?
Tetralogy of Fallot is a congenital heart condition, meaning children are born with it. The cause of the condition is not known. In some situations, it may be associated with certain genetic syndromes like trisomy 21, or the 22q11.2 deletion syndrome. Tetralogy also has one of the highest incidences of non-cardiac defects, so a detailed anatomy scan and genetic testing before birth is strongly recommended.
Surgery is the only definitive treatment for tetralogy of Fallot and babies diagnosed with this condition will require heart surgery after birth to correct the heart defect.
Babies with milder forms of the condition may not require surgery for a few months after birth. However, babies with severe pulmonary valve stenosis, pulmonary atresia or absent pulmonary valve will require surgery as newborns. If there is pulmonary atresia a cardiac catheterization is necessary to define the blood supply to the lungs, as, in this condition, collateral vessels from the aorta usually are the main blood supply to the lungs. The surgeries for tetralogy of Fallot with pulmonary atresia are quite complicated, and often require on-going catheterization procedures.
In patients with isolated tetralogy of Fallot and pulmonary stenosis, the outcomes of surgery are excellent, and a normal life can be anticipated. Additional surgeries are often needed to replace the pulmonary valve, which can leak (pulmonary insufficiency) , especially if the patient is repaired in the neonatal period. Replacement of the pulmonary valve is done to prevent the right ventricle from becoming too large (dilated)
Patients with tetralogy of Fallot are followed by a pediatric cardiologist; usually every year after surgery. At these visits an electrocardiogram (ECG) and an echocardiogram (echo) are usually performed. If the echo shows that the right ventricle (which gives rise to the pulmonary artery) is enlarging, a cardiac MRI scan is performed to accurately measure the volume of the right ventricle in anticipation of pulmonary valve replacement.
It the ECG is abnormal, or the patient is feeling skipped beats or has symptoms of arrhythmia, a 24 or 48-hour Holter monitor will help to diagnose the arrhythmia and the need, if any, for further studies or procedures.
When the child becomes an adult, he will transition to care provided by an adult congenital heart disease specialist. This is a physician who has training both in adult medicine and has done a congenital heart disease fellowship.
*diagnostic information provided courtesy of our partners at Colorado Fetal Care Center
The Fetal Health Foundation is a parent-founded non profit helping families experiencing a fetal syndrome diagnosis.