Editing Cardiac conduction system (section)

===Arrhythmia===
{{Main|Arrhythmia}}
An [[arrhythmia]] is an abnormal rhythm or speed of rhythm of the heartbeat. A slow [[heart rate]] of 60 or less beats per minute is defined as [[bradycardia]]. A fast heart rate of more than 100 beats per minute is defined as [[tachycardia]].
An arrhythmia is defined as one that is not [[physiological]] such as the lowered heart rate that a trained athlete may naturally have developed; the resting heart rates may be less than 60 bpm.

When an arrhythmia cannot be treated by [[Antiarrhythmic agent|medication]] (or other standard [[cardioversion]] measures), an [[artificial cardiac pacemaker|artificial pacemaker]] may be [[Implant (medicine)|implanted]] to control the conduction system.