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Tricuspid Atresia

Tricuspid atresia is a type of congenital heart disease in which the tricuspid valve fails to develop properly.  Typically there is simply a plate of tissue where the normal tricuspid valve should be. This results in no direct communication between the right atrium and right ventricle.  This defect was first described in 1817.  Today, studies have estimated its incidence at around 5-6 per 100,000 live births.  As many as 20% of those affected also have other heart defects.

Tricuspid atresia is almost invariably associated with some sort of hypoplasia, or underdevelopment of the right ventricle, due to the lack of adequate blood flow.  Various forms of tricuspid atresia are also classified based on the relationship of the two great arteries, the aorta and pulmonary artery.  Type I describes patients with normally related great arteries (the most common type, accounting for 70-80% of cases), and Type II refers to patients with transposed, or switched great arteries (12-25%).  Type III, an uncommon type of tricuspid valve atresia (3-6%), usually is associated with more complex abnormalities and malpositions.

Tricuspid atresia is classified as a cyanotic form of congenital heart disease. Cyanotic congenital heart disease refers to those heart defects that result in decreased or inadequate blood flow to the lungs. The term cyanosis refers to the blue discoloration of the skin that these infants and children typically have to due to low blood oxygen levels. In tricuspid atresia, because blood cannot pass from the right atrium to the right ventricle, it must flow across a hole between the two atria (termed a foramen ovale or atrial septal defect), where it then enters the left atrium and left ventricle. From here, some blood may be pumped out to the lungs through a hole between the ventricles (ventricular septal defect), but the majority usually is returned to the body. The amount of blood flow to the lungs is typically determined by factors such as the size of the VSD, the presence of any pulmonary stenosis, or the presence of transposition of the great arteries.

Infants with tricuspid valve atresia are usually cyanotic at birth, but depending on the specific type, this may not be noticed initially.  A heart murmur is almost always present. Diagnosis is typically made by echocardiography. Once the diagnosis is made, infants with tricuspid atresia usually require a medication called prostaglandin E1 (PGE-1) in order to maintain circulation of blood to the lungs.  PGE-1 allows for a normal fetal structure, the ductus arteriosus, to remain open. This acts as a source for blood to enter the lungs to receive oxygen.

Tricuspid atresia always requires surgical repair.  In order to re-route the deoxygenated blood to the lungs, multiple stages of surgical palliation are necessary.  The first stage involves placing an artificial shunt (a modified Blalock-Taussig shunt) in order to maintain blood flow to the lungs.  Following this surgery, the baby can usually go home, with close follow up by a pediatric cardiologist. 

The second stage, known as the Glenn procedure, is performed between 4-6 months of age.  During this surgery, the superior vena cava, the main vein carrying deoxygenated (blue) blood from the upper half of the body is disconnected from the heart and directly connected to the pulmonary artery.  In addition, the previously placed modified Blalock-Taussig shunt is removed.

The final stage, usually performed around 3 years of age, is known as the Fontan procedure.  This involves connecting the inferior vena cava, the vein draining blood from the lower part of the body back to the heart, directly to the pulmonary artery as well. Following this procedure, all deoxygenated blood flows passively back to the lungs, while the heart focuses solely on pumping oxygenated blood returning from the lungs back to the body.

Tricuspid atresia is one of the great success stories of the last 30 years in the treatment of congenital heart disease.  Currently survival to one year of age is in excess of 90% with survival at 5 to 10 years of age in excess of 85%.  As recently as the 1980s, many children born with tricuspida atresia did not survive infancy. Long-term complications associated with the Fontan procedure include issues such as blood clots, infections, and electrical disorders of the heart.  Other issues for families may include questions regarding participation in athletics, and considerations related to pregnancy in women who have survived into adulthood.  While the data on these issues is continually being revised, optimism is growing that more and more patients will be able to live relatively normal lives in the setting of major congenital heart defects such as tricuspid atresia.