The heart has 2 upper chambers called atria and 2 lower chambers called ventricles. Electrical signals move through special nerve bundles to the atria then to the ventricle. When the electrical signals pass through as expected the heart pumps rhythmically.

Heart block occurs when the electrical signals do not travel normally through the heart. The heart can still pump blood, but it beats much slower and less efficiently than normal. There are 3 types of heart block, ranging from mild to serious:

  • First-degree heart block—mildest form of heart block. Electrical signals reach all parts of the heart but move more slowly than normal. There are usually no symptoms, and heartbeat is normal.
  • Second-degree heart block—some of the electrical signals are not reaching the ventricles. This means that sometimes the ventricles do not pump when they should.
  • Third-degree, or complete, heart block—most serious type of heart block. No electrical signals are able to reach the ventricles. Cells in the ventricles act as a back up and create their own electrical signals. This allows the ventricles to keep pumping, but it is slower and out of rhythm with the rest of the heart. .

Anatomy of the Heart

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The causes of heart block in children may include:

  • Heart defect caused by genetics
  • Certain medications
  • Damage from surgery
  • Infections such as Lyme disease
  • Lupus in the mother
  • Electrolyte abnormalities
  • Autoimmune disorder

Risk Factors

Factors that may increase your child's chance of heart block include:

  • Previous heart problems like heart failure or heart attack
  • Heart valve problems
  • Certain medications
  • Exposure to toxic substances


Your child may not have any symptoms at all. If your child has any of the following, see the doctor.

  • Lightheadedness
  • Fainting
  • Chest pain
  • Shortness of breath
  • Rapid or slow heart beat
  • Weakness or fatigue

Be aware that your child may feel these symptoms, but may not be able to tell you or know how to describe them. Watch for signs, like:

  • Trouble keeping up with other children when playing
  • Needing to take resting breaks from playing


You will be asked about your child’s symptoms and medical history. A physical exam will be done.

The electrical activity of your child's heart may need to be tested. This can be done with an electrocardiogram (EKG).


The course of treatment will depend on the type of heart block. Generally, treatment is not needed for first-degree heart block.

A pacemaker may be needed for some cases of second-degree heart block and all cases of third-degree heart block. The pacemaker will send regular electrical signals to the heart. It will keep the heart beating in a more efficient rhythm.


Unfortunately, there is no way to prevent heart block in your child.


CardioSource—American College of Cardiology

Heart Rhythm Society


Canadian Cardiovascular Society

Heart and Stroke Foundation of Canada


Atrioventricular (AV) conduction disorders. EBSCO DynaMed Plus website. Available at: Updated November 27, 2017. Accessed December 21, 2017.

Heart block. Heart Rhythm Society website. Available at: Accessed December 21, 2017.

University of California San Francisco. Heart block. UCSF Benioff Childrens’ Hospital website. Available at: Accessed December 21, 2017.

Heart block. National Heart, Lung and Blood Institute website. Available at: Accessed December 21, 2017.

Last reviewed November 2018 by EBSCO Medical Review Board Kari Kassir, MD  Last Updated: 12/20/2014