@kuro Tetralogy of Fallot is a congenital heart defect that is present at birth. Symptoms include episodes of bluish color to the skin. When affected babies cry or have a bowel movement, they may develop a "tet spell" where they turn very blue, have difficulty breathing, become limp, and occasionally lose consciousness. Other symptoms may include a heart murmur, finger clubbing, and easy tiring upon breastfeeding.