Final answer:
Tet spells in babies with tetralogy of Fallot are characterized by episodes of cyanosis, where they turn bluish and could faint due to increased flow of oxygen-poor blood in the body.
Step-by-step explanation:
'Tet spells' in babies with tetralogy of Fallot refer to episodes when babies turn bluish and may faint. These spells are essentially an increase in the flow of oxygen-poor blood to the baby's body, and can be both a sign and a symptom of the underlying congenital heart condition. Tetralogy of Fallot is characterized by four heart defects that affect the structure of the heart, leading to an insufficient supply of oxygenated blood and subsequent cyanosis. During these 'tet spells' or hypercyanotic episodes, there might be an abrupt decrease in the amount of oxygen in the baby's blood, causing them to become very blue, which is known as 'blue baby syndrome.' Additionally, activities that change the pressure in the baby's heart can trigger these spells. The condition is often first observed when a baby is active, which can be feeding or crying, making this condition particularly challenging for infants.