Bradycardia is an abnormally slow or unsteady heart rhythm (usually less than 60 beats per minute) that causes symptoms such as dizziness, fainting, being extremely tired, and shortness of breath.

Diagnostic tests such as an electrogram (ECG) assist the doctor in discovering the specific cause of the bradycardia. When an irregular heart rhythm cannot be seen at the time of the test, an implantable loop recorder, the Reveal ILR, might be used to clarify the diagnosis. A pacemaker relieves the symptoms of bradycardia by increasing the heart rate to an appropriate rate.