Tricuspid atresia: what does it consist of?

Tricuspid atresia is a rare congenital heart malformation. It consists of the total absence of the tricuspid valve that divides the two compartments that make up the right side of the heart.

This results in significant hemodynamic alterations that can be life-threatening. If you are interested in learning a little more about the disorder, we invite you to follow this article.

Types of tricuspid atresia

This condition usually presents with other congenital malformations. Beyond being the result of genetic defects or problems during pregnancy, this is due to survival issues.

Since the tricuspid valve is vital for the proper functioning of the heart, its absence implies the need for alternative routes to appear for blood distribution. Therefore, additional defects occur so that the fetus can live after delivery.

How does the heart work?

In normal conditions, the heart consists of two sides that do not communicate (right and left) and four chambers or chambers that do communicate (the atrium at the upper level and the ventricle at the lower level). The right side handles blood without oxygen (deoxygenated), while the left pumps oxygenated blood.

Between the atria and ventricles there are valves that regulate the flow of blood: tricuspid for the right side and mitral for the left side. There are also valves between the ventricles and the great vessels that arise from them: the pulmonary on the right side and the aortic on the left side.

The right heart, which handles deoxygenated blood, pumps blood to the lungs to fill it with oxygen. This blood is returned to the left heart so that it can be pumped to all tissues in the body. In turn, the blood tissue is returned to the right heart for the cycle to repeat.

Discover more: The heart, the body's pump

Once this is clarified, we will describe two common types of tricuspid atresia, based on the presence of other malformations.

1. Tricuspid atresia with ventricular communication (VSD), interatrial communication (ASD) and pulmonary stenosis

Blood that enters the right atrium passes into the left atrium through the hole that forms the ASD. After that, the blood continues naturally to the left ventricle and part of it passes to the right ventricle through VSD.

Although blood from the right compartment of the heart should be able to flow naturally into the pulmonary circulation, there is a new obstacle: pulmonary stenosis.

In this condition, the valve that allows blood to exit the right ventricle into the lungs has an increase in resistance. Therefore, it is more difficult to pump.

2. Tricuspid atresia with transposition of the great vessels

The great vessels are the largest and originate from each ventricle. On the left side it is called aorta, which distributes oxygenated blood to all tissues. On the right side is the pulmonary artery, which, as its name suggests, carries deoxygenated blood to the lungs.

Transposition of the great vessels is a complex pathology, since the location of these structures is reversed. The aorta emerges from the right ventricle, while the pulmonary artery emerges from the left. Simply put, this causes the deoxygenated blood to never become oxygenated.

As in the previous case, for this condition to be compatible with life, communication between the cavities on the right side and those on the left side is necessary. VSD is a disorder that occurs frequently in these patients.

What causes it?

The fact that tricuspid atresia is a rare disease and that the relationship with family history is scarce, means that the mechanisms involved in its appearance are still not exactly known.

However, in a 2016 scientific review work the authors affirm that exposure to any of the risk factors that we will mention in the next section is likely to favor the appearance of genetic defects. These include mutations in the genes on chromosomes 3, 4, 8, and 22.

Risk factor's

According to the Mayo Clinic, these factors increase the probability that a baby will be born with this condition and the most frequent are the following:

• Inadequate prenatal care.
• Consumption of alcohol, tobacco or drugs teratogenic in pregnancy.
• Family history (especially in the parents) of tricuspid atresia.
• Infections during pregnancy: rubella.
• Metabolic diseases of the mother: Mellitus diabetes.
• Presence of Down syndrome in the baby.

As with many birth defects, exposure to some of these factors tends to be most damaging in the first two trimesters of pregnancy. This is a crucial stage in the development of the heart.

Keep reading: Prenatal diagnosis: what it consists of and what types of tests are there

What are your symptoms?

The symptoms are varied and largely depend on the type of associated malformations. As we mentioned before, these allow to reduce the effects of tricuspid atresia and distribute the blood in the best possible way. The most common are the following:

• Bluish discoloration of the skin and mucous membranes (cyanosis). This corresponds to a low degree of oxygenation of hemoglobin, which is contained in red blood cells or erythrocytes.
• Difficulty breathing (dyspnoea).
• Stunted growth with less weight and height.
• Fatigue.

Some patients may develop heart failure, a condition in which the heart is unable to adequately pump blood. Here, the aforementioned symptoms may worsen, in addition to swelling of various parts of the body (edema).

Diagnosis

When a high-risk pregnancy occurs, tricuspid atresia can be diagnosed before birth. This is accomplished using a fetal echocardiogram., despite the fact that the therapeutic options at this stage are limited.

After birth, the combination of clinical and paraclinical elements allows the doctor to make the diagnosis. These latest studies include the following:

• Plain chest x-ray.
• Electrocardiogram.
• Echocardiogram.

In some cases, cardiac catheterization could be useful to determine some hemodynamic parameters. These will influence the treatment of the disease.

How can it be treated?

Definitive treatment is surgical, since it allows to reestablish the normal anatomy of the heart. However, some conditions can delay the intervention, so it is necessary to resort to drugs and hemodynamic procedures to control symptoms.

When a newborn is born with severe cyanosis, treatment with prostaglandin E1 is usually indicated, with the aim of keeping a structure called ductus arteriosus. This is present in all developing fetuses, but under normal conditions it closes shortly after birth.

Tricuspid atresia: high risk

Tricuspid atresia is a complex condition and, without early diagnosis and prompt treatment, it can be fatal. From here comes the importance of having an adequate pre and postnatal control. In case of doubt, it is advisable to see a neonatologist or pediatrician as soon as possible.