Introduction

Tricuspid Atresia is a rare congenital heart defect in which the tricuspid valve is either absent or abnormally developed. This condition affects the normal flow of blood through the heart, specifically the tricuspid valve, which separates the right atrium from the right ventricle.¹ Disturbance in the In tricuspid atresia, normal bloodflow, i.e. from the right atrium to the right ventricle and then to the lungs for oxygenation, gets disturbed. This results in reduced blood and a lack of oxygen at various body sites, which can lead to symptoms and health problems.

The differential diagnosis of tricuspid atresia is important for the patient and the family’s understanding. Differential diagnosis is a term used to distinguish a disease or condition from others that have similar manifestations.^{1, 2} This article provides detailed information on tricuspid atresia, its symptoms, and how it is different from other congenital heart defects.

Tricuspid atresia

This is a congenital heart disease. In the normal heart, the tricuspid valve enables blood to pass through from the right atrium to the right ventricle.¹ From there, the blood is pumped to the lungs and picks up oxygen before being pumped back to the left side of the heart and out to the other end of the body.

In tricuspid atresia, there is a blood flow obstruction of the tricuspid valve, which is either absent or malformed. This then means that the blood does not pass from the right atrium to the right ventricle, and the right ventricle may be smaller than normal.^{2, 3} To compensate, the body develops other ways to get blood flowing around the body, such as an atrial septal defect (ASD) or ventricular septal defect (VSD) that allows blood to flow around the right ventricle and into the lungs.

Symptoms of tricuspid atresia

Tricuspid atresia affects the heart and triggers various other heart problems. Related symptoms depend on the severity of tricuspid atresia. Common symptoms include:

• Cyanosis (bluish tint to the skin, lips, and nails): This condition arises due to inadequately oxygenated blood³
• Shortness of breath: Due to the reduced oxygen supply to the body³
• Fatigue: Especially during physical activity, as the body struggles to meet its oxygen demands³
• Poor growth and development: Infants with tricuspid atresia may have difficulty gaining weight and growing at a normal rate³
• Heart murmur: An abnormal heart sound that a healthcare provider can detect during a physical examination³

Differential diagnosis of tricuspid atresia

Tricuspid atresia is a complex congenital heart defect; it should be differentiated from other disorders with similar symptoms. The differential diagnosis includes:

Pulmonary atresia with intact ventricular septum (PA/IVS)

Another congenital heart defect involving the lack of blood flow from the right ventricle to the pulmonary valve, which merges with the main artery leading to the rest of the body, is pulmonary atresia with an intact ventricular septum.⁴ In other words, PA/IVS does not involve a hole between the ventricles as the ventricular septum is intact.

Key differences

• The tricuspid valve is usually present in PA/IVS, but if it is small or dysfunctional.
• The PA/IVS is also characterised by the right ventricle in PA/IVS being hypoplastic (underdeveloped), just as in tricuspid atresia; however, the tricuspid valve differs from the latter.⁴

Ebstein's anomaly

A congenital heart defect that involves the malformed and abnormal position of the tricuspid valve. It can result in the backing of blood into the right atrium (tricuspid regurgitation) or reduced output to the lungs.⁵

Key differences

• Tricuspid atresia occurs when there is no (or severely diminished) tricuspid valve, and Ebstein's anomaly is present when the tricuspid valve is present but malformed.
• Tricuspid regurgitation is often prominent in Ebstein's anomaly but not in tricuspid atresia.

Tetralogy of Fallot (TOF)

Tetralogy of Fallot is a type of heart defect present at birth that includes the following problems:

• A hole between the heart’s lower chambers (ventricular septal defect)
• Narrowing of the valve leading to the lungs (pulmonary stenosis)
• The main artery (aorta) is shifted and lies over the hole between the chambers (overriding aorta)
• Thickening of the right lower heart chamber wall (right ventricular hypertrophy)⁶

Key differences

• In most cases of TOF, the tricuspid valve is usually normal. However, in tricuspid valvular atresia, the valve is either missing or very underdeveloped
• Tet spells, episodes of severe cyanosis, and breathlessness (less common in tricuspid Atresia) are common features of TOF⁶

Hypoplastic left heart syndrome (HLHS)

Congenital heart defect hypoplastic left heart syndrome causes a severely underdeveloped left side of the heart (left ventricle, mitral valve, aorta).

Key differences

• In HLHS, the left part of the heart is damaged, and in tricuspid atresia, the right part of the heart is mainly damaged⁷
• Nearly all infants with HLHS develop symptoms of heart failure shortly after birth. In contrast, infants with tricuspid atresia present with cyanosis, as well as less severe symptoms of heart failure

Transposition of the great arteries (TGA)

A congenital heart defect where the two large arteries coming out from the heart, the pulmonary artery and the aorta, are in the wrong position is a transposition of the great arteries. This means that blood without sufficient oxygen is sent to the body, while blood rich in oxygen is sent to the lungs.⁸

Key differencesś

• The tricuspid valve is usually normal in TGA, whereas in tricuspid atresia, the valve is absent or rudimentary
• TGA has severe cyanosis almost immediately after birth, while tricuspid atresia may be milder and may manifest only when other defects are also present

Total anomalous pulmonary venous return (TAPVR)

Total anomalous pulmonary venous return is a congenital malformation in which the pulmonary veins, which normally carry oxygen-rich blood to the left atrium from the lungs, are shunted to the right atrium or another vein.⁹

Key differences

• In TAPVR, the tricuspid valve is usually normal, while in tricuspid atresia, the valve is absent or poorly developed.
• Symptoms of heart failure and cyanosis are common in TAPVR, but the cause is different from tricuspid atresia.

Diagnostic tools for tricuspid atresia

Diagnostic tools used by healthcare providers in an attempt to accurately diagnose tricuspid atresia and differentiate it from other congenital heart defects may include:

Echocardiogram

An echocardiogram is an ultrasound of the heart, from which detailed images of the heart's structure and function can be seen. Among tricuspid atresia, it is the primary diagnostic tool to determine the absence or failure of the tricuspid valve and any associated structures.¹⁰

Electrocardiogram (ECG)

An electrocardiogram records the electrical activity of the heart and spots abnormalities of structure and heart rhythm. The ECG for tricuspid atresia may show signs of an enlarged right atrium and thickening of the left ventricular muscle.¹⁰

Chest X-ray

A chest X-ray can show the size and shape of the heart, the condition of the lungs, and other conditions in the chest area. In tricuspid atresia, the chest x-ray may have an enlarged heart and decreased pulmonary vascular markings.¹⁰

Cardiac catheterisation

Cardiac catheterisation is a procedure that involves the placement of a thin tube (catheter) into a blood vessel and advancing it to the heart. This procedure provides detailed information about the structure and blood flow to the heart and is often used to help plan a surgical intervention.^1,10

Magnetic resonance imaging (MRI)

Detailed images of the heart and blood vessels are obtained with cardiac MRI and used to evaluate the severity of tricuspid atresia, along with any associated defects.¹⁰

Treatment options for tricuspid atresia

Tricuspid atresia treatment involves a sequence of surgical procedures intended to enhance blood flow toward the lungs, and their oxygenated blood is pumped out to the body. The most common surgical interventions include:

Blalock-taussig shunt

The Blalock-Taussig shunt is a surgical procedure that connects the subclavian artery (a large artery in the arm) to the pulmonary artery. Because it increases blood flow to the lungs, it increases oxygenation.¹¹

Glenn procedure

The Glenn procedure is a type of vascular surgery in which the superior vena cava (the vein that carries blood from the upper body to the heart) is joined directly to the pulmonary artery. It decreases the burden on the right ventricle and also enhances the blood flow to the lungs.¹⁴

Fontan procedure

This involves directly connecting the inferior vena cava (the vein that carries blood from the lower body to the heart) with the pulmonary artery. It passes the circulation of oxygen-poor blood around the right ventricle to the lungs. This allows oxygen-poor blood to bypass the right ventricle. The final stage of surgical treatment of tricuspid atresia is the Fontan procedure.¹⁴

Summary

Tricuspid atresia is a very complex congenital heart disease requiring careful diagnosis and management. Tricuspid atresia is part of a differential diagnosis of congenital heart defects presenting with similar symptoms, such as Ebstein's anomaly, pulmonary atresia with intact ventricular septum, Tetralogy of Fallot, hypoplastic left heart syndrome, transposition of the great arteries, and total anomalous pulmonary venous return. The diagnosis is usually accurate and involves an echocardiogram, electrocardiogram, chest X-ray, cardiac catheterisation, and cardiac MRI.

The treatment for tricuspid atresia involves a series of surgical procedures to increase blood flow through the lungs, such as the Blalock-Taussig shunt, Glenn procedure, and Fontan procedure, to sustain oxygenation of the blood. Because a substantial number of patients are detected in this group early, early diagnosis and intervention are crucial to improving outcomes, quality of life, and complete survival for patients with tricuspid atresia.

With knowledge of the differential diagnosis and treatment options for tricuspid atresia, patients and their families can be well-prepared to face such a complex condition. This allows them to work with their healthcare provider to create the most appropriate treatment plan.