Tricuspid atresia is a type of congenital heart disease in which the valve between the right atrium and right ventricle fails to develop. Blood that returns from the body to the right atrium cannot directly enter the right ventricle, and must pass through a hole in the atrial septum (atrial septal defect) into the left atrium and then the left ventricle.
There are several anatomic variations that influence the symptoms and course of treatment in any given patient.
- If a ventricular septal defect (a hole in the ventricular septum) is present and the great arteries are in their normally related position, blood from the left ventricle can reach the lungs through the ventricular septal defect. This channel is often very narrow, and the right ventricle very underdeveloped, so a less than normal amount of blood goes to the lungs.
- If there is no ventricular septal defect or only a small one, and the great arteries are normally positioned, blood flows from the left ventricle out the aorta to the body. In this situation very little, if any, blood can get to the lungs resulting in very low oxygen levels in the infant.
- Finally, if there is transposition of the great arteries, blood reaches the lungs easily because the pulmonary artery is directly connected to the left ventricle. But blood can only reach the body through the ductus arteriosus or the ventricular septal defect if there is one.
In a newborn baby, blood can reach the lungs to pick up oxygen as long as a connection between the aorta and pulmonary artery called the ductus arteriosus remains open. The “ductus” is an important vessel while the baby is still in the womb because it allows the blood from the baby’s heart to return to the placenta, which does the job of the lungs before birth. When the baby is born, it typically narrows down (or closes completely) after 24 to 48 hours in response to the oxygen levels in the air breathed by the child. An intravenous medication called prostaglandin can keep this important vessel open after birth.
The signs and symptoms of tricuspid atresia depend on the presence and size of the ventricular septal defect, and the relationship of the great arteries. Symptoms may include:
- Cyanosis – a low oxygen level and a dusky, blue color
- Pulmonary edema – the lungs become engorged with blood, causing fluid to leak from the bloodstream into the air spaces of the lungs
- Low blood pressure
- Fast breathing
- Poor feeding
- Cold, clammy hands and feet
- Congestive heart failure – the combination of increased heart and lung work, using large amounts of calories. The symptoms of congestive heart failure are:
- Fast breathing
- Fast heart rate
- Sweating with feeds
- Poor weight gain
Infants presenting with these symptoms are critically ill and require emergency medical attention.
In a newborn baby (less than 1-2 weeks old), a medication called prostaglandin E1 can be given intravenously to reopen the connection (ductus arteriosus) between the pulmonary artery and aorta and improve blood flow to the lungs or body.
Children with tricuspid atresia and too little pulmonary blood flow will require surgery to establish a connection between the arteries to the body and the arteries to the lungs. This type of operation is call a modified Blalock-Taussig (BT) shunt, and involves the placement of a small Gore-tex tube between the artery to the arm (subclavian artery) and the arteries to the lungs (pulmonary artery).
If the problem is too much pulmonary blood flow (tricuspid atresia with a large ventricular septal defect), blood flow to the lungs will usually need to be limited to protect the lungs from becoming damaged by too much blood flow. This can be accomplished by placing a band around the pulmonary artery so that blood flow to the lungs is limited in a controlled way.
Finally, if the problem is inadequate blood flow through the aorta (tricuspid atresia with ventricular septal defect and transposition of the great arteries), blood from the normal size left ventricle will need to be routed to the aorta, and the aorta will usually need to be reconstructed. Pulmonary blood flow can then be established by placement of a modified BT shunt. This is essentially the Norwood procedure used for hypoplastic left heart syndrome.
Whatever operation is necessary in the newborn period, children can expect to undergo further heart surgery by the age of 3-6 months. This operation is called a Bi-directional Glenn. It allows blood from the upper body to flow directly to the lungs to pick up oxygen without having to be pumped by the heart. It also prevents blood that already has oxygen from returning to the lungs, and thereby keeps the heart from doing unnecessary work. After this operation, however, there is still blood returning from the body through the inferior vena cava going directly back to the body without first passing through the lungs. Because of this, some level of cyanosis will persist.
Between the ages of 2 and 5 years, the child will be ready for the third operation required to optimize their circulation. This operation is called the Fontan procedure, and involves connection of the inferior vena cava directly to the pulmonary artery, thereby forcing all blood returning from the body to pass through the lungs and pick up oxygen before being pumped to the body. This allows a more normal color in the skin and lips as well as a more normal oxygen saturation in the blood.
The results of this staged approach to the child with tricuspid atresia are generally good, with an expected survival of all three stages of 75 percent to 95 percent depending on the exact malformations and surgery for any given individual.
The long-term quality of life following the Fontan operation is generally good, however, several complications may occur. These include heart rhythm problems requiring medication or placement of a pacemaker. Patients may also experience lung problems resulting in a decrease in oxygen in the blood, or digestive problems caused by loss of protein in the stool resulting in swelling and water retention. For a minority of patients, heart and possibly lung transplantation may be necessary later in life.