Heart arrhythmia (also known as arrhythmia, dysrhythmia, or irregular heartbeat) is a group of conditions in which the heartbeat is irregular, too fast, or too slow.[2] A heart rate that is too fast – above 100 beats per minute in adults – is called tachycardia and a heart rate that is too slow – below 60 beats per minute – is called bradycardia.[2] Many types of arrhythmia have no symptoms.[1] When symptoms are present these may include palpitations or feeling a pause between heartbeats.[1] In more serious cases there may be lightheadedness, passing out, shortness of breath, or chest pain.[1] While most types of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure.[2][3] Others may result in cardiac arrest.[3]