What Is Tetralogy of Fallot?

Tetralogy of Fallot (teh-TRALL-o-gee-of-fal-O) is a congenital heart disease that includes 4 specific defects:

• Pulmonary valve stenosis (steh-NO-sis) is a narrowing of the pulmonary valve and the area below the valve. This slows the flow of blood from the right side of the heart to the lungs. The heart must pump harder to push blood through the smaller opening to the lungs where the blood picks up oxygen.
  
  
• Ventricular (ven-TRICK-u-lar) septal defect (VSD) is a hole in the wall that separates the lower chambers (ventricles) of the heart.
  
  
• Overriding aorta is a defect in the position of the large artery (aorta) that takes red (oxygen-rich blood) to the body. In a normal heart the aorta attaches to the left lower chamber of the heart (ventricle). In tetralogy of Fallot, the aorta sits between the left and right ventricles, over the VSD. This causes mixing of red and blue (oxygen-poor) blood.
  
  
• Right ventricular hypertrophy (hy-PER-trow-fee) is the thickening of the right lower chamber of the heart (ventricle). Unlike other muscles in your body, when the heart thickens it does not work well. The heart has to pump harder to move blood through the narrowed pulmonary valve and the area below it.

Tetralogy of Fallot is a serious and complex heart defect that is present at birth. A baby's heart forms shortly after conception. By the end of the second month of pregnancy, the baby's heart is completely formed. It is during this time that tetralogy of Fallot can occur. It causes:

• Less blood flow to the lungs
  
  
• Mixing of red (oxygen-rich) and blue (oxygen-poor) blood inside the heart
  
  
• Low levels of oxygen in the blood. When oxygen levels are low, the baby's skin, fingertips, or lips have a bluish tint. This is called a "blue baby" or cyanosis (SY-uh-NO-sis).

Each year in the United States about 3,000 babies are born with tetralogy of Fallot. It is the congenital heart disease that causes the most cases of cyanosis.

Every infant or child with tetralogy of Fallot needs surgery, usually within the first year of life. With advances in surgery and treatment many children born with tetralogy of Fallot have successful surgery and live to adulthood.

To better understand the effects of tetralogy of Fallot, go to the section on "How the Heart Works" with an image of a normal heart and a heart with tetralogy of Fallot.