8th March 2024

Tricuspid Atresia

This is the third most common form of cyanotic congenital heart disease and is characterised by an absent tricuspid valve and no direct communication between the RA and RV. The defect occurs during prenatal development and results in an absent or hypoplastic RV. If left untreated, the mortality rate is high (90%) at 1 year of age.

Image Source: Wikimedia Commons (2009). Tricuspid atresia, Licensed under a creative commons licence. Available for free at: https://en.wikipedia.org/wiki/Tricuspid_atresia (Accessed: 26 January 2024).

In many cases of tricuspid atresia, additional defects are present, which allow the exchange of blood between the systemic and pulmonary circulation. Associated conditions include:

• ASD 
• VSD
• Pulmonary outflow obstruction 
• Ventricular arterial discordance, including TGA
• Pulmonary artery anomalies 
  

Diagnosis

Most cases of tricuspid atresia are diagnosed during a routine anomaly scan. Central cyanosis is the most noticeable feature on physical examination. There may be tachypnoea in the first two weeks of life and a holosystolic murmur due to VSD. Diagnosis can be confirmed using an echocardiogram. 

Management

In neonates, prostaglandin E1 (PGE1) is given initially to maintain patency of the ductus arteriosus. Single-ventricular palliative surgery is then performed to ensure adequate separation between the pulmonary and systemic circulation. 

Palliative surgical intervention is usually performed in three stages:

1. Modified Blalock-Thomas-Taussig procedure: A Gore-Tex conduit is used to connect the subclavian artery to the pulmonary artery 
2. Cavo-pulmonary anastomosis (Bi-directional Glenn procedure): This includes redirecting the oxygen-depleted blood from the upper parts of the body to the lungs by connecting the superior vena cava to the right pulmonary artery. 
3. Fontan procedure: Venous blood is diverted from the IVC to the pulmonary arteries. This creates a system in which the entire venous system is now flowing passively into the pulmonary arteries. The single ventricle pumps oxygenated blood out of the left ventricular outflow tract (LVOT) into the systemic circulation, thus relieving cyanosis.