heart rate that is below the normal range

Bradycardia (also called bradyarrhythmia) is a slow heart rate. In adults, bradycardia is defined as a heart rate that is under 60 beats per minute (bpm) while the person is resting.[1] Bradycardia is a type of cardiac arrhythmia.

Sinus bradycardia seen in lead II with a heart rate of about 50.
ICD-9427.81, 659.7, 785.9, 779.81

There are many types of bradycardia. Some are caused by problems with the heart. Bradycardia can also be caused by medicines, drugs, and many other things.



The symptoms of bradycardia depend on how slow the heart rate is and what kind of problem the heart is having. For most people, bradycardia is not a serious problem. But it can become a serious problem if it signals a major problem with the heart. Also, if bradycardia gets very bad, the heart will be unable to pump enough blood and oxygen to the body. Every part of the body needs blood and oxygen to survive. If bradycardia is bad enough, it can cause organ damage, brain damage, and death.[2]


  • Problems with the heart's electrical system. There are two atria (upper chambers) in the heart: the right atrium and the left atrium. For the heart to beat normally, special parts of the right atrium have to send electricity through the heart to make it squeeze out blood. The electricity has to start in a certain place and pass through a certain route in the heart. If this does not happen correctly, the heart will not beat correctly.
  • Medications, like beta blockers
  • Depressant medications or drugs


  1. "Types of Arrhythmia". July 1, 2011. Retrieved 19 March 2015.
  2. "Arrhythmias and Conduction Disorders". The merck Manuals: Online Medical Library. Merck Sharp and Dohme Corp. January 2008. Archived from the original on 7 December 2009. Retrieved 16 December 2009.