What is Congenital Tricuspid Atresia?
Tricuspid atresia is a type of congenital (a condition you are born with) heart disease. In this disease, the valve between the right atrium and right ventricle doesn’t develop.
Blood that returns from the body to the right atrium cannot directly enter the right ventricle. It must pass through a hole in the atrial septum (atrial septal defect) into the left atrium and then the left ventricle.
There are several differences that can produce different symptoms. The treatments depend on the defect and symptoms.
There may be a hole in the ventricular septum, called a ventricular septal defect (VSD).
The aorta and pulmonary artery may be normally positioned and in line with the appropriate ventricle (as shown in illustration). Or, they may be reversed, a condition called transposition of the great arteries.
If the ventricular septal defect is small or absent, and the great arteries are normally positioned, blood flows from the left ventricle out the aorta to the body. In this situation very little, blood can get to the lungs. This leads to very low oxygen levels in the infant.
In a newborn baby, blood can reach the lungs to pick up oxygen if 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. It allows the blood from the baby's heart to return to the placenta. The placenta does the job of the lungs before birth.
This vessel is sensitive to oxygen. When the baby is born, it closes completely after 24 to 48 hours. An intravenous medication called prostaglandin (PGE) can keep this vessel open after birth.
If a ventricular septal defect 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.
Finally, if there is transposition of the great arteries, blood reaches the lungs easily. This happens because the pulmonary artery is directly connected to the left ventricle. But blood can only reach the body and organs through the ductus arteriosus or the ventricular septal defect if there is one.
Signs and Symptoms of Tricuspid Atresia
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.
Most commonly, the great arteries are normally related and there is either no ventricular septal defect or only a small ventricular septal defect. In this case, the newborn with tricuspid atresia will have a low oxygen level and a dusky, blue color, also called cyanosis. This cyanosis may be noted at birth or may only become evident after several days when the ductus arteriosus closes. As the ductus closes the cyanosis worsens. If the cyanosis is severe enough, the baby will develop symptoms of poor oxygenation such as fast breathing or poor feeding.
Occasionally, there is an increased amount of blood flow to the lungs. This baby may have little to no cyanosis but will likely develop congestive heart failure because of this imbalance.
The increased workload on the left ventricle and easier path of blood flow to the lungs causes them to become engorged with blood and causes fluid to leak from the bloodstream into the air spaces of the lungs. This condition is called pulmonary edema and makes it harder for a baby with this condition to breathe comfortably.
The combination of increased heart and lung work uses large amounts of calories and results in the constellation of symptoms referred to as congestive heart failure (CHF).
The symptoms of congestive heart failure are fast breathing, fast heart rate, sweating with feeds and poor weight gain. If there is transposition of the great arteries, the presenting symptoms are related to low blood flow through the aorta and out to the body. This results in low blood pressure, fast breathing, poor feeding, cold, clammy hands and feet, and a pale, gray color.
Infants presenting with these symptoms are critically ill and require emergency medical attention.
Diagnosis of Tricuspid Atresia
Babies with tricuspid atresia may or may not have a heart murmur. The amount of oxygen in the blood can be easily and painlessly measured using a machine called a pulse oximeter.
Based on the symptoms reported by the parents and physical examination of the child, the physician will be prompted to order further tests to evaluate the heart.
The diagnosis of tricuspid atresia and the associated specific problems such as a ventricular septal defect or transposition of the great arteries can be very accurately diagnosed by echocardiography. This involves using an ultrasound machine to make pictures of the heart and to show the direction and, in some cases, the amount of blood flow through various parts of the heart and blood vessels.
Treatment of Tricuspid Atresia
The diagnosis of tricuspid atresia with too little blood flow to the lungs or to the body requires immediate medical treatment. In a newborn (less than 1 to 2 weeks old), a medication called PGE 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 called a modified Blalock-Taussig (BT) shunt and involves the placement of a small 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 to 6 months. This is true whether the child has too much or too little pulmonary or systemic blood flow in the newborn period and, therefore, did not require any surgery at that time.
The operation at 3 to 6 months is called a bidirectional Glenn. The superior vena cava is detached from the heart and connected directly to the pulmonary artery, and the BT shunt is removed. This 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, children with tricuspid atresia 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, which forces 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 due to a more normal oxygen saturation in the blood.
Treatment of Tricuspid Atresia: Results
The results of this staged approach to the child with tricuspid atresia are generally good, with an expected survival through 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 with the oldest patients currently in their 30s. 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.