What Is Tricuspid Atresia?
Tricuspid atresia is a birth defect of the tricuspid valve, which is the valve that controls blood flow from the right atrium (upper right chamber of the heart) to the right ventricle (lower right chamber of the heart). Tricuspid atresia occurs when this valve doesn’t form at all, and no blood can go from the right atrium through the right ventricle to the lungs for oxygen. Because a baby with tricuspid atresia may need surgery or other procedures soon after birth, this birth defect is considered a critical congenital heart defect. Congenital means present at birth.
In a baby without a congenital heart defect, the right side of the heart pumps oxygen-poor blood from the heart to the lungs through the main pulmonary artery. The blood that comes back from the lungs is oxygen-rich and can then be pumped to the rest of the body through the aorta. In babies with tricuspid atresia, the tricuspid valve that controls blood flow from the right atrium to the right ventricle is not formed, so blood is unable to get to the right ventricle and out to the lungs. For this reason, the right ventricle can be underdeveloped. The main pulmonary artery may also be small with very little blood going through it to the lungs.
In tricuspid atresia, since blood cannot directly flow from the right atrium to the right ventricle, blood must use other routes to bypass the unformed tricuspid valve. Babies born with tricuspid atresia often also have an atrial septal defect, which is a hole between the right and left atria, or a ventricular septal defect, which is a hole between the right and left ventricles. These defects allow oxygen-rich blood to mix with oxygen-poor blood, so that oxygen-rich blood has a way to get pumped to the rest of the body.
Doctors may give the baby medicine to keep the baby’s patent ductus arteriosus (PDA in the image) open after the baby’s birth. The PDA is the blood vessel that allows blood to move around the baby’s lungs before the baby is born, and it usually closes after birth. Keeping this connection open allows blood to get to the lungs for oxygen and bypass the small right side of the heart.
Some babies with tricuspid atresia can also have other heart defects, including transposition of the great arteries (TGA). In TGA, the main connections (arteries) from the heart are reversed. The main pulmonary artery, which normally carries oxygen-poor blood from the right side of the heart to the lungs, now arises from the left side and carries oxygen-rich blood returning from the lungs back to the lungs. The aorta, which normally carries blood from the left side of the heart to the body, now arises from the right side and carries oxygen-poor blood back out to the body. When a baby has both tricuspid atresia and TGA, blood is able to get to the lungs because the main pulmonary artery arises from the developed left ventricle. However, blood cannot get out to the body because the aorta arises from the poorly formed right ventricle and is small.
Source: Centers for Disease Control and Prevention (CDC)