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Tetralogy of Fallot

Tetralogy of Fallot is a combination of four heart defects that can result in a baby turning blue or cyanotic because of a lack of oxygen in the blood. It usually is diagnosed in infancy.

The heart consists of four chambers: the two upper chambers, called atria, where blood enters the heart; and the two lower chambers, called ventricles, where blood is pumped out of the heart. Valves that act as one-way doors control the flow between the chambers and between the arteries. The heart also has been pictured as two side-by-side pumps with one side pumping blood into the lungs and the other side pumping blood from the lungs back to the body.

Blood is pumped from the right side of the heart up through the pulmonary valve and the pulmonary artery to the lungs, where the blood is filled with oxygen. From the lungs, the blood travels back down to the left atrium and left ventricle and is then pumped through another big blood vessel called the aorta to the rest of the body.

The four defects characteristic of this condition include:

  • An abnormal opening in the wall separating the ventricles called a ventricular septal defect (VSD) that allows blood to go directly from the right to left ventricle without going through the lungs.
  • A narrowing of pulmonary valve or below the valve called pulmonary stenosis that partially blocks blood flow to the lungs.
  • An overly muscular right ventricle, also called right ventricular hypertrophy.
  • A displaced aorta, also called overriding aorta or Ao, directly over the abnormal opening between the ventricles.

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A complete cardiac evaluation for tetralogy of Fallot will include:

  • Echocardiography, in which a picture is made of the heart by using sound waves
  • Chest X-ray
  • Electrocardiogram (EKG or ECG), which records the heart's electrical activity
  • Examination of the oxygen content of arterial blood. This is usually done with an oximeter, a little light that can be placed on a finger. Sometimes, a blood sample may be drawn from an artery in the wrist and checked for content of oxygen, carbon dioxide and acidity.

The defects usually are corrected during a single operation done when the baby is about 6 months old unless the baby has inadequate oxygen. If the baby is too small, there may be two surgical procedures. The first procedure connects the pulmonary arteries to the aorta or its branches by a tube called a shunt to supply blood to the lungs. Later surgery enlarges the pulmonary valve opening and closes the ventricular septal defect (VSD) with a patch so that blood flows easily into the pulmonary artery and lungs. The shunt is then removed.

Most people with tetralogy have had corrective surgery by the time they reach their teens. If they have only had shunts placed, they probably will need to have a complete repair including shunt removal.

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Reviewed by health care specialists at UCSF Medical Center.

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