Tricuspid Atresia

Introduction

Tricuspid Atresia is a severe congenital heart disease characterized by the absence or failure of the tricuspid valve to open, preventing normal blood flow from the right atrium to the right ventricle. This condition results in a hypoplastic right ventricle and the need for intracardiac shunts to maintain pulmonary circulation. Blood oxygenation depends on the presence of an atrial septal defect (ASD) and often a ventricular septal defect (VSD).
Tricuspid Atresia accounts for approximately 1-2% of congenital heart diseases, with an estimated incidence of 1 in 10,000 live births. It is frequently associated with other anomalies, such as transposition of the great arteries and pulmonary stenosis.

Anatomy and Pathophysiology

Tricuspid Atresia results from an abnormal development of the tricuspid valve, which is completely closed or absent. Consequently:

• Venous blood cannot flow directly into the right ventricle, leading to right atrial overload.
• The right ventricle is hypoplastic and does not contribute significantly to pulmonary circulation.
• Venous blood passes through an atrial septal defect (ASD) into the left atrium, mixing with oxygenated blood.
• Pulmonary circulation depends on a patent ductus arteriosus (PDA) or a ventricular septal defect (VSD) that allows blood to reach the lungs.

The severity of cyanosis and hypoxemia depends on the amount of blood reaching the lungs for oxygenation.

Clinical Presentation

Affected newborns develop symptoms within the first hours or days of life, characterized by:

• Cyanosis, due to the mixing of venous and arterial blood.
• Fatigue and feeding difficulties, secondary to hypoxemia.
• Heart murmur, often present in cases of ventricular septal defect.
• Signs of heart failure, particularly in cases with excessive pulmonary blood flow.

Without timely intervention, hypoxemia can rapidly worsen.

Diagnosis

Tricuspid Atresia can be diagnosed prenatally through fetal echocardiography. After birth, confirmation of the diagnosis is based on:

• Echocardiography: identifies the absence of the tricuspid valve, the presence of an ASD, and associated anomalies.
• Cardiac catheterization: useful for assessing cardiac anatomy and pulmonary pressures.
• ECG: may show left axis deviation and right atrial hypertrophy.
• Chest X-ray: may reveal a small heart with decreased pulmonary blood flow.

Treatment

Treatment is exclusively surgical and follows a **multi-stage approach**, including:

• Neonatal management: administration of prostaglandins (PGE1) to keep the ductus arteriosus open and support pulmonary blood flow.
• Systemic-to-pulmonary shunt (Blalock-Taussig shunt): creation of an artificial passage between the aorta and the pulmonary artery to ensure oxygenation in the first months of life.
• Glenn procedure: anastomosis of the superior vena cava to the pulmonary artery to reduce cardiac overload.
• Fontan procedure: completion of the separation between pulmonary and systemic circulation, typically performed in late childhood.

In more complex cases, heart transplantation may be considered.

Prognosis

Thanks to advances in pediatric cardiac surgery, survival in patients with Tricuspid Atresia has significantly improved. However, long-term quality of life depends on the success of palliative procedures, with the possibility of requiring additional interventions in adulthood. Major complications include **arrhythmias, venous thrombosis, cardiac dysfunction, and pulmonary hypertension**.

References
1. Rao P.S. et al. Tricuspid Atresia: Current Concepts in Diagnosis and Management. J Am Coll Cardiol. 2020;76(4):398-412.
2. Jacobs M.L. et al. Outcomes of Surgical Repair in Tricuspid Atresia. Ann Thorac Surg. 2019;108(5):1142-1154.
3. Gatzoulis M.A. et al. Long-term Follow-Up in Tricuspid Atresia Patients. Circulation. 2018;137(12):2099-2112.
4. Brigham K.L. et al. Modern Surgical Approaches to Tricuspid Atresia. J Thorac Cardiovasc Surg. 2021;162(3):740-755.
5. Freedom R.M. et al. Pediatric Cardiac Anomalies: The Case of Tricuspid Atresia. Pediatr Cardiol. 2021;42(1):150-168.
6. Bove E.L. et al. Fontan Procedure: Outcomes and Challenges. J Am Coll Cardiol. 2020;145(2):205-218.