Because of multiple levels of right heart obstruction, most children with Tricuspid Atresia require a Patent (open) Ductus Arteriosis (PDA) after birth to maintain adequate pulmonary (lung) blood flow. When the PDA closes soon after birth (see diagram at lower right), there is inadequate blood flow to the lungs and the body becomes starved for oxygen-rich (red) blood and the patient will show worsening cyanosis, or blueness. These children may become very ill and require surgery to increase the blood flow to the lungs.