What Is Tetralogy of Fallot?

Tetralogy of Fallot is the most common heart defect in children. The condition causes mixing of oxygen-poor blood with the oxygen-rich blood being pumped out of the heart and into the circulatory system of blood vessels.

 

- Tetralogy of Fallot is a rare, complex heart defect that occurs in about 5 out of every 10,000 babies. It affects boys and girls equally.

 

• - The blood leaving the heart has less oxygen than is needed by the organs and tissues of the body, a condition called hypoxemia.
  
  
• - Chronic lack of oxygen causes cyanosis, a bluish color of the skin, lips, and membranes inside the mouth and nose.

 

To understand this defect, it's helpful to know how a healthy heart works. The Diseases and Conditions Index How the Heart Works article describes the structure and function of a healthy heart. The article also has animations that show how your heart pumps blood and how your heart's electrical system works.

 

 

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Tetralogy of Fallot involves four heart defects:

• A large ventricular septal defect (VSD)
• Pulmonary stenosis
• Right ventricular hypertrophy
• An overriding aorta

 

 

Ventricular Septal Defect

The heart has a wall that separates the two chambers on its left side from the two chambers on its right side. This wall is called a septum. The septum prevents blood from mixing between the two sides of the heart.

 

A VSD is a hole in the part of the septum that separates the ventricles, the lower chambers of the heart. The hole allows oxygen-rich blood from the left ventricle to mix with oxygen-poor blood from the right ventricle.

 

Pulmonary Stenosis

This defect is a narrowing of the pulmonary valve and the passage through which blood flows from the right ventricle to the pulmonary artery.

 

Normally, oxygen-poor blood from the right ventricle flows through the pulmonary valve, into the pulmonary artery, and out to the lungs to pick up oxygen. In pulmonary stenosis, the heart has to work harder than normal to pump blood, and not enough blood reaches the lungs.

 

Right Ventricular Hypertrophy

This defect occurs if the right ventricle thickens because the heart has to pump harder than it should to move blood through the narrowed pulmonary valve.

 

Overriding Aorta

This is a defect in the aorta, the main artery that carries oxygen-rich blood to the body. In a healthy heart, the aorta is attached to the left ventricle. This allows only oxygen-rich blood to flow to the body.

 

In tetralogy of Fallot, the aorta is between the left and right ventricles, directly over the VSD. As a result, oxygen-poor blood from the right ventricle flows directly into the aorta instead of into the pulmonary artery to the lungs.

 

Outlook

Together, these four defects mean that not enough blood is able to reach the lungs to get oxygen, and oxygen-poor blood flows out to the body.

 

 

Normal Heart and Heart With Tetralogy of Fallot

 

 

 

Figure A shows the structure and blood flow in the interior of a normal heart. Figure B shows a heart with the four defects of tetralogy of Fallot.

 

Babies and children who have tetralogy of Fallot have episodes of cyanosis. This is a bluish tint to the skin, lips, and fingernails. Cyanosis occurs because the oxygen level in the blood is below normal.

 

Tetralogy of Fallot must be repaired with open-heart surgery, either soon after birth or later in infancy. The timing of the surgery depends on how severely the pulmonary valve is narrowed.

 

Over the past few decades, the diagnosis and treatment of tetralogy of Fallot have greatly improved. As a result, most children who have this heart defect survive to adulthood. However, they’ll need lifelong medical care from specialists to help them stay as healthy as possible.