What is tricuspid atresia? 

Tricuspid atresia is a congenital condition which stems from the malformation of the heart. 

The heart normally has 4 chambers: the right atrium takes blood to the right ventricle, which sends blood to the lungs for oxygen via the pulmonary vein, and then the left atrium sends blood to the left ventricle, which pumps this oxygenated blood around the body so your body can keep making energy and keep you alive. The way the blood moves from atrium to ventricle on each side of the heart is through valves, which on the right side of the heart is through the tricuspid valve.¹

During pregnancy, blood typically flows from the right atrium to the left atrium and around the baby’s body because the mother's blood already has oxygen from her lungs, and it is this that is pumped around the baby's body and heart.  

Nevertheless,  blood does fill the heart, and this is what allows all 4 chambers of the heart to develop properly. After birth, this small hole that takes blood directly from the right atrium to the left atrium (Foramen ovale) closes up, and the baby can continue breathing, oxygenating blood as it is pumped around the body.

In tricuspid atresia, the valve between the right atrium and right ventricle isn't formed, and instead, solid tissue blocks the way.¹ Consequently, during pregnancy, blood doesn't flow through the right ventricle, and it remains underdeveloped. The foramen ovale, which takes blood directly from the right atrium to the left, remains open, and this allows deoxygenated blood to be pumped around the heart. The lungs have been missed, and so it doesn't gain oxygen. Often, this is ok because the blood in the left ventricle is sent to both the lungs and out to the body. So overall, with each pump, there will be blood sent around the body that has at least some blood that has been to the lungs to collect oxygen.¹ However, the oxygen levels in this blood will be lower than average, thus leading the baby to get tired much more easily, and possibly causing them to breathe rapidly to try and get lots of oxygen into the body quickly.

An open foramen ovale and a hole connecting the right and left ventricles (which may be underdeveloped) describe type I tricuspid atresia.¹

The switching of the pulmonary vein and the aorta, in addition to this, describes type II tricuspid atresia, with possible issues in the valves of the pulmonary vein.¹

Type III consists of these issues along with other issues about the position of the heart's chambers and vessels.¹

4/5 of those with tricuspid atresia will have type I, and very rarely would type III ever occur.¹ To take a closer look at how this serious condition can be fixed, read on.

How can tricuspid atresia be treated?

There are a few different ways tricuspid atresia can be treated. This includes drugs to keep the foramen ovale open after birth and surgery to turn the solid tissue between the right atrium and right ventricle into a valve/ opening. Balloon septostomy is also an option.

Understanding balloon septostomy

Balloon septostomy is a procedure to get more oxygen into the bloodstream of the baby, and although this is only a temporary fix, it can be quite effective.²

A catheter is inserted into the bloodstream, guided to the heart and inflated in the foramen ovale to widen the gap/ create a new one if this has closed. This provisional fix allows more oxygen to enter the bloodstream, therefore allowing the baby to make enough energy to stay alive. This can be done in emergency situations, soon after birth, to keep the baby alive, or it can be done to help improve the baby’s strength before further surgery can be carried out to fix the defects.^2,3 It provides stability and allows the baby’s condition to improve, especially when there is a risk of cyanosis or other heart issues that also exist, such as a patent ductus arteriosus.^3,4

The procedure- balloon septostomy 

The procedure involves the use of a long, hollow tube of plastic called a catheter. In this case, the catheter has a small balloon attached at the tip, which can be inflated at will with an external pump. This catheter is inserted into the body through a vein in the groin (the common femoral vein or umbilical vein), and threaded through the venous system through the abdomen, finally entering the heart through the inferior vena cava (the main vein that takes deoxygenated blood from the body and takes it to the heart).³

Using echocardiographic guidance, the catheter is carefully positioned to ensure that the balloon is in the correct location before it is inflated slowly with saline (or sometimes a contrast solution), with precise monitoring to prevent ripping a hole in the heart or damage to surrounding structures. The balloon is then pulled back across the wall between the atria, thereby creating an opening large enough to allow blood to flow from the right atrium into the left atrium.^1,3 If the opening has closed significantly, this can also be used to create an opening as the tissue between the 2 atria, where the foramen ovale used to be, will still be soft. 

Preventing damage to the valves in the heart or the pulmonary veins is important, as well as ensuring that the opening created in the place of the foramen ovale is sufficiently large to improve oxygen levels in the bloodstream but not so large that it causes complications. 

After a balloon septostomy procedure, the baby’s health is closely watched to make sure everything stays stable.³ Doctors and nurses will keep track of vital signs, such as the baby’s blood pressure, heart rate, and oxygen levels. To help with this, a blood pressure cuff is used to check the baby’s blood pressure regularly, usually every two minutes, and it’s best placed on the right arm.³ They also check oxygen levels in two places: the right arm (pre-ductal) and the legs (post-ductal). The right arm measures the oxygen level before the blood mixes, and the legs measure after the blood has passed through the lungs, where it picks up oxygen.³ This helps doctors see if the baby’s oxygen levels are normal or if there’s any problem. As the right leg may have been used for the procedure, the blood pressure would not be measured here to prevent false readings.³

Additionally, the baby’s ETCO2 (End-Tidal Carbon Dioxide) levels are monitored. This is a way to measure how well the baby is breathing by checking the amount of carbon dioxide in the air they exhale. If the baby is not breathing well or if there’s any issue with their breathing, this will show up in the ETCO2 levels.

If the initial balloon septostomy is unsuccessful or if complications arise, additional procedures or interventions may be required in a specialised catheterisation lab.

Complications and considerations

While balloon septostomy is generally considered safe and effective, it is not without potential risks. One of the primary risks is the possibility of creating a hole that is too large, leading to an imbalance in blood flow between the two atria. This could cause excessive mixing of oxygenated and deoxygenated blood, potentially leading to circulatory complications.^2,3 In rare cases, the procedure may also result in damage to the heart's walls or other structures.

While balloon septostomy is generally considered a safe and effective procedure, it does carry certain risks, including bleeding from the catheter insertion site, transient arrhythmias (abnormal heart rhythms), and potential injury to the heart structures.^1,3,5 Rarely, if the procedure doesn’t work and the baby is turning blue, surgical septostomy may be necessary to ensure that the deoxygenated blood can reach the lungs in sufficient amounts quickly enough.^1,3

Post-procedural monitoring is essential to ensure that the baby remains stable and that there are no complications. Continuous monitoring of heart function, oxygen levels, and neurological status is required in the immediate period following the procedure. Additionally, if the femoral vein is used for catheterisation, monitoring for signs of reduced blood flow to the lower limbs is necessary to detect any other issues with blood circulation.

As the fix is only temporary, the baby may undergo further surgeries, such as the creation of a body-to-pulmonary artery shunt or the Fontan procedure, to establish more permanent blood flow patterns as the baby grows.

Summary

Tricuspid atresia is a serious condition which is present from birth due to the heart structures being incorrectly formed.¹ Balloon septostomy can be used to improve this in emergency situations or when the baby is too weak to withstand a surgical correction of the malformation(s). Tricuspid atresia may be present on its own or with other heart/ genetic issues, which can influence which type the baby experiences and how treatment is administered. 

Balloon septostomy looks at improving blood flow from the right atrium directly into the left atrium, most commonly in tricuspid atresia type 2, thus allowing sufficient amounts of blood to reach the lungs and gain oxygen before it is pumped around the body. This can improve respiration and strength, stabilising the baby for further procedures. It is, however, only a temporary fix because it doesn’t improve the other issues, e.g. the solidly closed tricuspid valve or normalisation of blood flow patterns. It can, in some cases, be their best chance for survival, and later surgeries can help address these issues.