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 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 ready .
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 . As a result of veno-arterial mixing, many effects are seen in children with tricuspid atresia. 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.