Tricuspid atresia is one of the least common forms of congenital heart disease.

In a normal body, unoxygenated blood flows into the right atrium, then through the tricuspid valve to the right ventricle and on to the lungs. If the tricuspid valve is absent or malformed, blood cannot pass from the right atrium to the right ventricle and therefore cannot enter the lungs to be oxygenated.

For unoxygenated blood to reach the lungs, it must flow from the right atrium into the left atrium through a hole called the foramen ovale, which is a passageway in the fetal heart that normally closes shortly after birth. From the left atrium, blood then flows to the left ventricle and then either to the right ventricle, through a hole called a ventricular septal defect (VSD), or to the aorta.

If blood flows from the left ventricle to the aorta, another fetal passageway that normally closes, called the ductus arteriosus, allows some of the blood to flow into the pulmonary artery. This supplies the lungs with less than optimal blood flow and puts a strain on the left ventricle, which must now pump the blood supply for both the body and the lungs.

Infants with tricuspid atresia generally are cyanotic (bluish discoloration of skin) due to the mixing of deoxygenated blood with the normally oxygenated blood in the aorta. They rapidly become short of breath (dyspneic).

Various surgical approaches have been developed and vary depending on the age of the individual at the time the surgery is done.

• cyanosis (bluish discoloration of the skin)
• easily fatigued
• shortness of breath (dyspnea)
• clubbing of fingers or toes

This condition may be discovered during routine prenatal ultrasound imaging or upon examination shortly after birth. Cyanosis may be present from birth. A heart murmur is generally present at birth and may increase in loudness over several months.

Tests may include the following:

• ECG -- may show left ventricular hypertrophy
• echocardiogram -- will show absent tricuspid valve and small right ventricle for difinitive diagnosis
• chest X-ray -- may show heart enlargement
• cardiac catheterization (rarely performed)

Surgery is required to repair the effects of tricuspid atresia. Operative strategies depend on whether the lungs are receiving too little or, occasionally, too much blood. In the most common situation, a series of operations is required.

The first, done within the first few days of life, is a BT shunt. This consists of a surgically formed conduit or tunnel that attaches a large artery in the chest to the pulmonary arteries, the vessels that deliver unoxygenated blood to the lungs.

The next step is a Glenn procedure, in which the superior vena cava, the vessel that drains unoxygenated blood from the head and arms, is attached to the pulmonary arteries. The BT shunt is removed.

The final stage is the Fontan procedure, in which the the inferior vena cava, which drains unoxygenated blood from the lower body, is also attached to the pulmonary arteries. After the third procedure, the patient is no longer cyanotic. The Fontan procedure is usually done at about 2-3 years of age.

• sudden death