Any cardiac rhythm other than the normal sinus rhythm. Such a rhythm may be either of sinus or ectopic origin and either regular or irregular. An arrhythmia may be due to a disturbance in impulse formation or conduction or both. The phenotype is Arrhythmia (HP_0011675). Also known as: Abnormal heart rate, Arrhythmias, Cardiac arrhythmia, Cardiac arrhythmias, Cardiac rhythm disturbances, Heart rhythm disorders, Irregular heart beat, Irregular heartbeat.