Irregular heart rhythm. It’s a common cardiac condition, but most people with this problem experience a heart beating too fast. A less common type of arrhythmia (abnormal heart rhythm) is known as bradycardia. This condition happens when the heart rate is too slow.
Bradycardia is a heart rate of less than 60 beats per minute. It can be caused by various problems, including problems with the heart's sinus node, which acts as a kind of natural pacemaker.
It may also be caused by problems in the conduction pathways of the heart. This means that electrical impulses are not being conducted from the atria to the ventricles, so the heart’s regular rhythm is disrupted.
Other causes include metabolic problems such as hypothermia, or damage from a heart attack or heart disease.