Heart palpitations are defined as perceived abnormal heartbeats. Palpitations can occur in temporary, and generally harmless, disruptions in cardiac rhythm. When the heartbeat becomes much more intense and fast over a short time period, it is called paroxysmal tachycardia. In the majority of cases, however, palpitations occur with no underlying pathological cause, and are often due to stress, following physical strain, in cases of extreme fatigue, or prior to a vasovagal episode. An electrocardiogram is regularly performed in order to verify there is not accompanying cardiac pathology or proven rhythm disorder.