Triscupid Atresia is a condition where the TRICUSPID VALVE, which guards the junction between the right atrium and the right ventricle, is either ABSENT or is IMPERFORATE - that is, it does not have an opening to allow blood flow across it. There are many ways the valve can be imperforate - the leaflets of the valve may be formed but tightly stuck to each other, or may not be formed at all, with muscle tissue of the heart forming a wall where the valve should have been.

What happens in tricuspid atresia ?

What is immediately apparent is that blood cannot flow across the tricuspid valve from the right atrium into the right ventricle. And if there is no alternate route, circulation of blood is not possible. But Mother Nature always has the solution to such problems. In addition to the absence of a normal tricuspid valve, patients with tricuspid atresia have a "hole" in the wall between the right atrium and left atrium - an Atrial Septal Defect (ASD).
Blood returning to the right atrium from the veins crosses the ASD into the LEFT atrium. It then flows into the left ventricle, from where it may take a variable path. This path depends on the presence of other defects, like pulmonary stenosis and transposition of the great arteries (TGA).
We have seen, in an earlier article on Tetralogy of Fallot, about VENO-ARTERIAL MIXING. This is a situation where "impure" venous blood mixes with "pure" oxygen-rich arterial blood. It occurs in tricuspid atresia too, when blood mixes across the ASD.
As a result of veno-arterial mixing, many effects are seen in children with tricuspid atresia. First is the presence of bluish discoloration - called "cyanosis". Cyanosis occurs because of an abnormally low amount of oxygen in blood entering the arteries. Next, the risk of paradoxical embolism is present in tricuspid atresia patients.
The further clinical course of these patients depends on other defects being present as well. If there is pulmonary stenosis - that is, narrowing of the pulmonary valve, which guards the junction of the right ventricle with the blood vessel entering the lungs (pulmonary artery) - blood flow into the lung is reduced, causing deep cyanosis and necessitating early repair. If there is transposition of great arteries, blood flow into the aorta may be reduced if the Ventricular Septal Defect (VSD), which is always present in these cases, is very small.

How can Tricuspid Atresia be repaired ?

 

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