Tricuspid atresia is a rare, life-threatening birth defect of the heart that arises when one of its valves, the tricuspid valve, does not form during a fetus’s development. When babies are born with this condition, blood is unable to flow from the upper right chamber of their heart (the right atrium) to the lower right chamber (the right ventricle). This disrupts the normal flow of blood through the heart, limiting its ability to pump blue (deoxygenated) blood to the lungs to pick up oxygen. As a result, the blue blood is directed across a normal opening (called the patent foramen ovale) in the wall between to the two upper chambers to the left side of the heart and, thus, to the body. The combination of these two scenarios limits the supply of oxygen-rich blood throughout the body.

Babies born with tricuspid atresia may have a bluish discoloration of their skin and mouth, heart failure, as well as difficulty breathing and eating. About 400 babies with tricuspid atresia are born in the United States each year. The condition occurs equally in males and females.

About half of newborns with tricuspid atresia exhibit signs of the condition on their first day of life, which leads to an early diagnosis. The other half are diagnosed within their first month of life.

When a baby is born with tricuspid atresia, surgery—often within the first few days or weeks of life—is needed to redirect blood flow through the heart. Patients undergo surgical procedures that gradually improve the condition so that oxygen-rich blood travels throughout the body. Without treatment, most patients with tricuspid atresia will die during the first year of life. However, with surgical intervention, the chances of longer-term survival increase substantially. For instance, the 20-year survival after a Fontan procedure—the last of a three-stage sequence of surgeries for children with tricuspid atresia—ranges from 61% to 85%.

Tricuspid atresia is a serious congenital (present at birth) heart defect caused by the absence of a crucial heart valve. While the fetus’s heart is being formed, the tricuspid valve does not develop; instead, a solid ridge of tissue appears where this valve should be. Normally, blood flows from the right atrium to the right ventricle through the tricuspid valve. In patients with tricuspid atresia, blood from the right atrium cannot reach the right ventricle because of the barrier.

In a patient with a healthy heart, oxygen-poor blood, which has traveled throughout the body, enters the heart through the right atrium, and then passes through the tricuspid valve to the right ventricle. Next, blood passes through the pulmonary valve and enters the main pulmonary artery. Here, blood picks up oxygen in the lungs and becomes oxygen-rich (or oxygenated). This oxygen-rich blood returns to the heart’s left atrium, passes through the mitral valve to the left ventricle and, finally, through the aortic valve to the aorta, a large artery that delivers oxygen-rich blood throughout the body.

When a patient has tricuspid atresia, oxygen-poor blood enters the right atrium, but because no tricuspid valve exists, the blood cannot pass to the right ventricle. Because this chamber of the heart is not used, patients with tricuspid atresia often have an underdeveloped right ventricle. They may also have a narrowed (or obstructed) main pulmonary artery.

Some patients with tricuspid atresia may have other congenital heart defects, such as:

• Atrial septal defect (ASD). Many patients with tricuspid atresia have a hole in the heart wall between the heart’s upper chambers (called an atrial septal defect), which allows oxygen-poor blood to enter the left side of the heart, where it may travel through the aorta to the rest of the body.
• Foramen ovale. In some cases, newborns may have another hole between the atria, called the foramen ovale. This is a normal opening in the heart wall in a fetus that typically closes in the first days of a newborn’s life.
• Ventricular septal defect (VSD). Some patients with tricuspid atresia also have a hole in the heart wall between the heart’s lower chambers (called a ventricular septal defect), which allows some blood to travel from the left ventricle to the right ventricle. Once blood is in the right ventricle, it can travel through the main pulmonary artery to pick up oxygen before entering the left side of the heart, the aorta, and traveling to the rest of the body. This provides the body with some oxygen-rich blood, although the blood that travels through the left side of the heart is a mixture of oxygen-poor and oxygen-rich blood. If the pulmonary arteries are obstructed or narrowed, less oxygen-rich blood will pass through.
• Patent ductus arteriosus (PDA). In a fetus, the ductus arteriosus is a special blood vessel that connects the pulmonary artery to the aorta. This blood vessel usually closes within the first days of a baby’s life; if it stays open, it’s known as a patent ductus arteriosus. This condition may allow the blood in a patient with tricuspid atresia to reach the lungs, enabling oxygen-rich blood to travel throughout the body.
• Transposition of the great arteries. In some cases, the arteries connected to the heart are in the wrong positions. The pulmonary artery normally delivers oxygen-poor blood from the right half of the heart to the lungs, where it becomes oxygen-rich, but it may instead direct oxygen-rich blood back to the lungs. The aorta normally brings oxygen-rich blood from the left half of the heart to the body, but it may instead send oxygen-poor blood from the heart’s right half throughout the body.

Doctors aren’t sure what causes tricuspid atresia. Certain genetic or chromosomal abnormalities may contribute to the condition.

Babies with tricuspid atresia experience one or more of the following symptoms:

• Bluish skin
• Difficulty breathing
• Fatigue or extreme sleepiness
• Difficulty feeding
• Poor weight gain
• A heart murmur

Having German measles (rubella) or another viral illness during early pregnancy may increase a baby’s risk for the condition. In a small number of cases, tricuspid atresia runs in families.

In some cases, doctors can diagnose tricuspid atresia during pregnancy after a routine ultrasound, which uses sound waves to create images of the fetus. If doctors suspect tricuspid atresia after an ultrasound, they offer a fetal echocardiogram, which uses ultrasound to create detailed images of a fetus’s heart.

After birth, doctors are able to diagnose tricuspid atresia after learning about a baby’s medical history, performing a physical exam, and offering diagnostic tests. This is often picked up by state-mandated critical congenital heart disease screening (using pulse oximetry) before newborns are discharged from the hospital after birth.

When a newborn has bluish skin and difficulty breathing, doctors may ask the parents if the baby was diagnosed with another heart defect during pregnancy.

During a physical exam, doctors will look at the baby’s skin, observe their breathing and listen to their heart with a stethoscope. They may hear a murmur or other heart abnormality.

Diagnostic tests used to confirm a diagnosis of tricuspid atresia include:

• Pulse oximetry. Newborns are routinely screened with this test, which measures blood-oxygen levels. Bluish skin and low blood-oxygen levels may be signs of tricuspid atresia. To check a newborn’s blood-oxygen levels, doctors connect an adhesive strip to a hand and/or a foot to get a reading.
• Chest X-ray. This imaging exam may show heart enlargement, including the right atrium, which may be a sign of tricuspid atresia.
• Echocardiogram (or “echo”). This diagnostic test is an ultrasound exam. It uses sound waves to create images of the patient’s heart, which come from a transducer (wand) placed on the patient’s chest and torso. This exam can show the structure of the heart and how blood flows through it. In patients with pulmonary atresia, it may show the absence of a tricuspid valve, an underdeveloped right ventricle, and a narrowed main pulmonary artery. It may also show an ASD, a VSD, a foramen ovale, and/or a PDA, as well as abnormal blood flow through the heart.
• Electrocardiogram (ECG or EKG). This test shows the electrical activity of the heart, measured by sensors attached to the patient’s chest and torso. When a baby has tricuspid atresia, the exam may show an enlarged right atrium, an underdeveloped right ventricle, and the presence of abnormalities on the left side of the heart.
• Cardiac catheterization. Sometimes, doctors use this diagnostic test to get more information about the conditions affecting the heart, including a PDA or an ASD. To perform this examination, doctors make a small incision in a blood vessel in the patient’s groin, then thread in a thin, flexible tube with a camera on its end. The catheter is sent through blood vessels until it reaches the heart, where doctors can observe the structures in question.

Patients with tricuspid atresia need more than one surgical procedure to improve their health. Over the course of a few years, doctors perform different procedures to reroute blood flow. In many cases, a newborn with tricuspid atresia needs surgery within the first days or weeks of life.

A newborn may first be given prostaglandin E1, a medication that helps the ductus arteriosus remain open, to help the baby’s blood reach the lungs to pick up oxygen.

The subsequent procedures are dependent on whether or not there is obstruction at the pulmonary valve level.

If there is obstruction, then the baby will need intervention/surgery in the first few weeks to establish blood flow to the lungs.

On the other hand, if there is a big VSD and no obstruction at the level of the pulmonary valve, there may be too much flow to the lungs. In those babies, sometimes, pulmonary artery banding is performed to reduce heart failure symptoms.

There are three stages of surgical/catheter based procedures needed for tricuspid atresia:

• Stage 1:
  • Blalock-Taussig-Thomas (BTT) shunt. Within the first weeks of life, patients may undergo this procedure, during which doctors place an artificial blood vessel to encourage blood flow between the aorta and the pulmonary artery, enabling more oxygen-rich blood to be pumped out of the heart and throughout the body.
  • PDA stent: This is a minimally invasive alternative to the BTT shunt offered through a cardiac catheterization procedure. In this case, doctors will place a stent in the ductus arteriosus to keep it open and provide blood flow to the pulmonary artery and, as a result, the lungs.

• Stage 2:
  • Bidirectional Glenn (BDG) Procedure. When the baby is 4 to 6 months old, doctors perform another procedure, known as the bidirectional Glenn shunt. The procedure involves the superior vena cava, a large vein that transports oxygen-poor blood from the upper half of the body to the right atrium of the heart. The bidirectional Glenn procedure redirects oxygen-poor blood from the top half of the body directly to the lungs, thereby bypassing the heart.
    
    Because blood that enters the right atrium cannot follow its intended path to the lungs due to the lack of a tricuspid valve, the Glenn shunt bypasses this part of the heart. The superior vena cava is connected to the pulmonary artery, which allows oxygen-poor blood from the body to pass through the lungs to become oxygenated, before passing through the left side of the heart and to the rest of the body. At the time of BDG, the previous BTT shunt or PDA stent is taken down.

• Stage 3:
  • Fontan procedure. When a patient is usually around 3 years old (though sometimes can be offered as early as 1.5 years), doctors perform a Fontan procedure to further improve blood flow throughout the body. This is the final procedure, and it is effective enough that patients stop appearing bluish after it is completed. During the Fontan procedure, doctors repair an atrial septal defect or other opening, and they connect the inferior vena cava, bringing oxygen-poor blood from the lower half of the body to the right pulmonary artery instead of the right atrium. This enables oxygen-poor blood from both halves of the body to flow directly to the pulmonary arteries, where blood can become oxygenated before traveling throughout the body. Together, these procedures bypass the unformed tricuspid valve and allow oxygen-rich blood to travel throughout the body.

If tricuspid atresia is left untreated, patients usually die within the first year of life. But patients with tricuspid atresia who undergo all three surgical procedures experience improvement in their symptoms. Their skin stops appearing bluish because oxygen-rich blood is able to circulate throughout the body, their appetite increases, and they regain energy. People who undergo a Fontan procedure, for example, are projected to have a 30-year survival rate of 85%.

Patients with tricuspid atresia should be monitored by a cardiologist for the rest of their lives due to the risk of complications associated with their condition.

Possible complications of tricuspid atresia that has been treated include heart-rhythm problems (arrhythmias) or blood clots in the brain or lungs. Some patients may need to take blood thinners to prevent the formation of blood clots.

“The Yale Children’s Heart Center offers the full range of expertise and care, from fetal life to adulthood, for those who are living with tricuspid atresia,” says Yale Medicine pediatric cardiologist Ruchika Karnik, MBBS. “The fetal cardiology program is critical in making an early diagnosis during fetal life and provides detailed counseling to the families about what to expect and a roadmap for it.”

The Pediatric Cardiac Interventional team offers cutting-edge and minimally invasive alternatives, such as stenting of the PDA to open heart surgery, Dr. Karnik adds. “With state-of-the-art equipment, the Advanced Congenital Cardiac Imaging Program provides additional imaging modalities to guide the various surgical procedures,” she says. “More importantly, the children naturally transition into the Adult Congenital Heart Program as they enter adulthood, all under the same roof without losing access to care as their needs change.”