Total anomalous pulmonary venous return is a very serious congenital heart defect that can have grave consequences if it is not treated promptly. The most serious complications of total anomalous pulmonary venous return are lung congestion (when the lungs are filled with too much blood), heart failure, and ultimately death. These conditions can occur within a few days to weeks after birth. If the heart defect is not treated, bluish discoloration of the skin, called cyanosis, will signal the baby’s worsening condition. Damage to the blood vessels of the lungs may eventually become irreversible. If blood flow to the body is not established, the condition is fatal.