Heart Block

Heart block occurs when the electrical impulses that make the heart beat do not transmit normally. Normally, these impulses travel from the heart's upper chambers, called the atria, to the lower chambers, called the ventricles, through the atrioventricular (AV) node. In heart block, the AV node may be damaged from surgery, medications or congenital heart conditions. Heart block affects the heart's ability to pump blood and the body's blood pressure, and can cause an abnormally slow heart rhythm called bradycardia. An implanted artificial pacemaker can restore a normal heart rate and rhythm.

Heart block may cause the following symptoms:

  • Chest pressure or pain
  • Fainting, also known as syncope, or near-syncope
  • Fatigue
  • Lightheadedness or dizziness
  • Palpitations, which can be skipping, fluttering or pounding in the chest
  • Shortness of breath

It is important to note that during a period of heart block, children may not know how to describe what they are feeling. They may have trouble keeping up with other children or realize they are having "spells" and want to sit down and rest. Sometimes, a child does not experience any symptoms at all.

Heart block may occur spontaneously with unpredictable timing. Therefore, in some cases, specialized tests may be needed to make an accurate diagnosis. If your doctor suspects that your child has heart block, he or she will order one or more of the following diagnostic tests to determine the cause of your child's symptoms.

  • Electrocardiogram (ECG or EKG) — An ECG records the heart's electrical activity. Small patches called electrodes are placed on your child's chest, arms and legs, and are connected by wires to the ECG machine. The electrical impulses of your child's heart are translated into a graph or chart, enabling doctors to determine the pattern of electrical current flow in the heart and to diagnose arrhythmias.
  • Show More

Heart block can be treated with the implantation of a permanent pacemaker, which regulates the heart beat. It consists of two parts — the generator and the lead. The generator is a small metal container with a battery and tiny computer. The lead is an insulated wire that carries electrical impulses to the heart to ensure a stable heartbeat.

The computer in the pacemaker is constantly monitoring your child's heartbeat. This is called sensing. When the pacemaker senses your child's heartbeat, it continues to monitor your child's heart and does not send a signal to stimulate the heart to beat. However, if no electrical impulse is detected by the pacemaker, it sends out a signal to stimulate your child's heart to beat.

For information on how a pacemaker is implanted, please see Pediatric Pacemaker Procedure.

Learn More

UCSF Research & Clinical Trials

Other Resources


Reviewed by health care specialists at UCSF Benioff Children's Hospital.

Related Information

UCSF Clinics & Centers

Heart Center

Arrhythmia Center
1825 Fourth St., Sixth Floor
San Francisco, CA 94158
Phone: (415) 514-2783
Fax: (415) 353-4144
Appointment information

Pediatric Heart Center Clinic at Mission Bay
1825 Fourth St., Sixth Floor
San Francisco, CA 94158
Phone: (415) 353-2008
Fax: (415) 353-4144
Appointment information

Cardiac Intensive Care Unit
1975 Fourth St., Fourth Floor
San Francisco, CA 94158
Phone: (415) 353-1955
Fax: (415) 353-9144

Related Conditions