Health Library

Tetralogy of Fallot

How is Tetralogy of Fallot Diagnosed?

When a newborn with significant cyanosis is first seen, they are often placed on supplemental oxygen. The increased oxygen improves the child's oxygen levels in cases of lung disease. Breathing extra oxygen will have little effect on the oxygen levels of a child with tetralogy of Fallot.

If a child doesn’t get better with oxygen, this is often an important clue to suspect a cyanotic cardiac defect. Infants with tetralogy of Fallot can have normal oxygen levels if the pulmonary stenosis is mild (referred to as "pink" tetralogy of Fallot). In these children, the first clue to suggest a cardiac defect is hearing a loud murmur when the infant is examined.

Once congenital (present from birth) heart disease is suspected, echocardiography can rapidly and accurately find the four related defects that make up tetralogy of Fallot.

Cardiac catheterization or CT scan is sometimes needed to see the size and distribution of the pulmonary arteries. Catheterization and CTs can also show whether patients have pulmonary blood flow coming from an abnormal blood vessel from the aorta (aortopulmonary collateral).

> View 2-D graphic summary of Tetralogy of Fallot

> View 3-D graphic summary of Tetralogy of Fallot

How is Tetralogy of Fallot Treated?

Once tetralogy of Fallot is diagnosed, the first thing to do is check whether the child's oxygen levels are in a safe range.

If oxygen levels are dangerously low soon after birth, a prostaglandin infusion is usually started to keep the ductus arteriosus open. This offers more pulmonary blood flow and increases the child's oxygen level.

Infants who need a prostaglandin infusion to have adequate oxygen levels will usually need surgery in the first few weeks of life. Infants with normal oxygen levels or only mild cyanosis are usually able to go home in the first week.

Complete repair is usually done electively when children are 4-6 months of age, as long as the oxygen levels stay adequate. If oxygen levels drop over time or suddenly, a child may need corrective repair sooner.

Surgery is always needed to correct the defects. Sometime patients will need a more minor surgery before the final correction.

Corrective repair of tetralogy of Fallot involves closing the ventricular septal defect with a synthetic patch so that the blood can flow normally from the left ventricle to the aorta.

The narrowing of the pulmonary valve and right ventricular outflow tract is then widened by cutting away muscle tissue in the right ventricle and enlarging the outflow pathway.

Rarely, the coronary arteries branch across the right ventricular outflow tract where the patch would normally be placed. In these babies, an incision (cut) in this area to place the patch would damage the coronary artery, so this cannot safely be done In this case, a hole is made in the front surface of the right ventricle (avoiding the coronary artery) and a conduit (tube) is sewn from the right ventricle to where the pulmonary arteries split, to provide open blood flow from the right ventricle to the lungs.

What is the Prognosis for Children With Tetralogy of Fallot?

Survival of children with tetralogy of Fallot has improved dramatically. If they have no additional risk factors, more than 95% of infants with tetralogy of Fallot successfully have surgery in the first year of life.

Most babies are fairly sick in the first few days after surgery, since the right ventricle is "stiff" from the previous muscle thickness and because a cut is made into the muscle of the ventricle, making the muscle temporarily weaker.

This problem usually improves significantly in the days after surgery. Patients may also have rhythm problems after surgery.

An abnormally fast rhythm (called junctional tachycardia) may happen and may need treatment with medication or the use of a temporary pacemaker. This abnormal rhythm is usually temporary. The rhythm generally will return to normal as the right ventricle recovers.

Patients are also at risk for slow heart rates after surgery due to heart block. Heart block may be caused by injury to or inflammation (swelling) of the conduction system in the heart. In many patients, the conduction gets better and normal rhythm returns. Rarely, a permanent pacemaker may be needed.

Since normal circulation is produced by the tetralogy of Fallot repair procedure, long-term heart function is usually excellent. In some patients, the pulmonary valve is able to be preserved, and they have no ongoing problems. Unfortunately, most patients do have issues. The most important issue is leakage (regurgitation) of the pulmonary valve. This can enlarge the right heart chambers and lead to limits on physical activity as well as heart rhythm problems and occasionally sudden cardiac death. Symptoms of fatigue (tiredness), especially with exercise, may happen. In these cases, replacing the pulmonary valve is often recommended, typically in the teenage years or in young adulthood. In many cases, pulmonary valves can be replaced using valves inserted through catheters (such as a Melody valve), rather than through surgery. This is usually a low-risk procedure that can allow the heart to shrink again. This can improve the patient’s quality of life and life expectancy. These artificial pulmonary valves usually last many years in adult patients but need ongoing follow-up checks.

Patients who have had repair of tetralogy of Fallot can also redevelop a narrowing in the right ventricular outflow area or in the branch (left or right) pulmonary arteries, which will cause the right ventricle to pump at abnormally high pressures. If these problems happen, more surgery to further widen the outflow tract or pulmonary arteries may be needed. Narrowing of the pulmonary arteries can sometimes be treated without surgery, with balloon dilation of the vessels during cardiac catheterization.

Most patients with repaired tetralogy should have regular (usually yearly) exams by a congenital heart expert. Follow-up visits in the cardiology clinic usually consist of a physical examination, electrocardiogram and periodic echocardiography.  These visits will also include occasional cardiac MRI scans, exercise stress tests, and Holter evaluations as a child reaches their teenage and adult years. Most adult patients with tetralogy of Fallot have had surgery to repair it in childhood. Long-term follow-up with a cardiologist to find any recurrent or new problems as early as possible is very important.