Tricuspid atresia is a congenital heart defect in which the tricuspid valve does not form properly. Instead, the heart muscle tissue here grows stronger, restricting blood flow and causing the right ventricle to underdevelopment, so often accompanied by a unique ventricular systole. Infants, children, or adults with tricuspid atresia can't get enough oxygen through the body, so they get tired easily, often have trouble breathing, and have bluish-blue skin.