Tricuspid atresia – an overview

Tricuspid Atresia (TA) is a critical congenital heart defect that occurs when the heart does not form at all. TA is characterised by the absence or severe underdevelopment of the tricuspid valve, which normally regulates blood flow between the right atrium (upper right chamber of the heart) and right ventricle of the heart (the lower right chamber).¹ 

In babies with this condition, the blood cannot flow correctly through the heart as well as to the rest of the body and because of this, the blood cannot correctly reach the lungs.¹ This means that when babies are born with TA, they may need surgery or other procedures very soon after birth. As this condition significantly disrupts the normal circulation of blood, it can lead to a complex set of symptoms and clinical presentations.   

Complications of tricuspid atresia

In a healthy heart, the tricuspid valve ensures the unidirectional flow of blood without oxygen from the right atrium to the right ventricle.¹ In TA, this valve is absent or malformed, obstructing the blood flow.² Because of this, the blood without oxygen from the body will find alternative routes to reach the lungs to pick up oxygen.³ 

Common compensatory mechanisms include atrial septal defect (ASD), which is a hole in the wall separating the right and left atria, allowing blood to shunt from the right atrium directly into the left atrium; and patent foramen ovale (PFO), a persistent opening between the atria, facilitating blood flow from the right to the left atrium.^4,1 These shunts, while essential for survival, lead to a mixing of oxygenated and deoxygenated blood, resulting in the blood having less oxygen delivered to the body.

Some babies with TA can also have dextro-Transposition of the Great Arteries (d-TGA). In d-TGA, the arteries from the heart are reversed; that is, the main pulmonary artery now arises from the left side, carrying oxygen-rich blood from the lungs back to the heart. This is reversed because the main pulmonary artery normally carries oxygen-poor blood from the right side of the heart to the lungs. Additionally, in d-TGA, the aorta arises from the right side and carries oxygen-poor blood back out to the body, instead of carrying blood from the left side of the heart to the body.¹

What causes TA?

The cause of TA is unknown. Sometimes it happens because of abnormalities in the babies’ genes or chromosomes. A combination of these genes with other factors like the mother’s environment, what she drinks or eats, or the medicines she uses, can lead to TA in their babies.¹ 

Signs and symptoms of TA

Babies that are born with tricuspid atresia will show symptoms at birth or very soon afterwards. These symptoms can include cyanosis, which is a bluish skin colour, since the abnormal blood flow makes it more difficult to get the oxygen that the babies need.¹ Other symptoms can include breathing problems, poor feeding and extreme sleepiness.¹ 

Clinical presentation

The clinical presentation of TA can vary significantly depending on the severity of the defect and the presence of associated anomalies.²  In early infancy, the clinical presentation includes: ^1,5 

• Cyanosis (a bluish colour of the skin, lips, and nails due to inadequate oxygenation of the blood)
• Tachypnea ( rapid breathing)
• Tachycardia (rapid heart rate)
• Poor feeding (the fatigue and decreased energy due to the lack of oxygen make it difficult for the babies to eat)
• Failure to thrive (the babies have poor weight gain despite their adequate caloric intake); and finally
• Diaphoresis (excessive sweating, particularly during feeding)

The clinical presentation during later infancy or childhood includes:

• Difficulty in practising physical activities⁶ 
• Squatting episodes, as the children may instinctively squat to increase systemic vascular resistance, thereby improving blood flow to the heart and brain
• Fainting due to the inadequate blood flow to the brain
• Clubbing (abnormal widening and thickening of the fingertips and toes)
• Polycythaemia (increased red blood cells)

Testing and diagnosis of TA

Comprehensive physical examinations and diagnostic tests need to be done to diagnose TA. To determine if someone has TA, they must demonstrate some of the following symptoms/abnormalities in the physical examinations and the diagnostic testing. 

There are some physical examination findings:

• Heart Sounds: A single second heart sound (S2) may be present. Murmurs may be audible depending on the presence and severity of associated defects, such as ventricular septal defects or pulmonary stenosis^{1, 7}
• Pulmonary Findings: Increased respiratory rate, potential presence of crackles or wheezes⁸
• Other Findings: Cyanosis (may be variable), clubbing of the fingers and toes, signs of congestive heart failure (if present)

The diagnostic tests for TA include:

• Electrocardiogram (ECG): May demonstrate right ventricular hypertrophy and other abnormalities
• Chest X-ray: May reveal an enlarged heart and increased pulmonary vascular markings
• Echocardiogram: The most crucial diagnostic tool, providing detailed images of the heart structures, including the absent or hypoplastic tricuspid valve, and assessing blood flow dynamics²
• Cardiac Catheterisation: May be necessary for further evaluation, particularly for assessing the severity of associated lesions and for therapeutic interventions⁹

Summary

Tricuspid Atresia (TA) is a critical congenital heart defect where the tricuspid valve, crucial for blood flow within the right side of the heart, is absent or severely underdeveloped. This abnormality forces blood to find alternative routes, often through existing holes in the heart's walls.

Clinically, infants with TA may present with cyanosis (bluish discolouration), rapid breathing, difficulty feeding, and poor weight gain. Older children may experience exercise intolerance, fainting spells, and clubbing of the fingers.

Diagnosis involves a comprehensive evaluation, including physical examination, electrocardiogram (ECG), chest X-ray, and echocardiogram. Echocardiography is particularly crucial for visualising the heart structures and assessing blood flow. TA significantly disrupts normal blood circulation, leading to decreased oxygen levels throughout the body. Treatment often involves multiple surgeries to improve blood flow and oxygenation. Early diagnosis and intervention are essential for optimal outcomes in children with TA.

FAQs

What is tricuspid atresia?

Tricuspid Atresia (TA) is a serious congenital heart defect where the tricuspid valve, which normally controls blood flow between the right atrium and right ventricle of the heart, is absent or severely underdeveloped. This prevents blood from flowing correctly within the heart.

What are the causes of tricuspid atresia?

The exact cause of TA is often unknown. It is believed to be a complex interplay of genetic and environmental factors.

What are the common symptoms of tricuspid atresia?

In infants, cyanosis (bluish discolouration of the skin), rapid breathing, poor feeding, failure to thrive, and excessive sweating are symptoms of tricuspid atresia. In older children, it can be exercise intolerance, fainting spells, clubbing of the fingers and toes.

How is tricuspid atresia diagnosed?

• Physical Examination: Doctors may observe cyanosis, rapid heart rate, and abnormal heart sounds
• Electrocardiogram (ECG): To assess heart rhythm and electrical activity
• Chest X-ray: To examine the size and shape of the heart and lungs
• Echocardiogram: An ultrasound of the heart to visualise the structures and blood flow
• Cardiac Catheterisation: May be needed for further evaluation and potential interventions

What are the treatment options for tricuspid atresia?

Treatment typically involves multiple surgeries to improve blood flow and oxygenation. These may include palliative procedures to improve blood flow temporarily, as well as the Fontan procedure, which is a complex surgery to reroute blood flow, bypassing the right ventricle.

What are the long-term outcomes for children with tricuspid atresia?

With advancements in medical care, many children with TA can live relatively normal lives. However, lifelong monitoring and management are essential.

Can children with tricuspid atresia participate in sports?

Many children with TA can participate in physical activities, but the level of activity will depend on the individual's condition and treatment plan.

Does tricuspid atresia affect cognitive development?

While some children with TA may experience developmental delays due to low oxygen levels, with appropriate treatment and management, most children with TA develop normally.

What is the role of genetics in tricuspid atresia?

While the exact genetic causes are still being researched, it is believed that genetic factors play a role in the development of TA.

What is the prognosis for children with tricuspid atresia?

The prognosis for children with TA has significantly improved with advancements in medical care. However, it varies depending on the severity of the defect, the presence of other heart abnormalities, and the overall health of the child.