What is Tetralogy of Fallot?

Tetralogy of Fallot (TOF) is a serious heart defect. Children born with TOF have four structural problems with their heart:

  • ventricular septal defect (VSD): a hole between the two lower chambers (ventricles) of the heart
  • right ventricular outflow tract obstruction: a narrowing of the connection between the heart and the artery that goes to the lungs
  • overriding aorta: the major blood vessel that connects the heart to the body (aorta) is too far to the right
  • right ventricular hypertrophy: a thicker-than-normal chamber The right-sided pumping chamber (ventricle) is thickened because it’s pumping blood against too much pressure

These defects mean that not enough blood may reach the lungs to get oxygen and the rest of the body doesn’t receive enough oxygen in the blood to maintain good health.


The first sign of TOF is often a bluish tint to the skin, fingernails and lips. This is caused by a low level of oxygen in the blood. Some babies may also have tet spells, during which they turn deep blue, breathe faster than normal and may cry or be very irritable. Other symptoms can include poor weight gain or becoming tired with feeding. The pediatrician will usually hear a heart murmur as an early indicator.


To help diagnose TOF, your child’s cardiologist may order one or more of the following tests:

  • echocardiogram (cardiac ultrasound)
  • electrocardiogram (EKG)
  • cardiac magnetic resonance imaging (MRI)
  • chest x-ray
  • cardiac catheterization
  • pulse oximetry (skin probe to assess oxygen levels)


Most babies with TOF need open-heart surgery before they are 6 months old to correct their heart defects.

Learn more about Pediatric Cardiology services at Boston Children’s Health Physicians.

Our second opinions bring peace of mind

Getting a second opinion from one of our clinicians will give you the peace of mind that comes from knowing your child’s health is in expert hands. Simply call 844-463-2247 to make an appointment with one of our specialists.