An abnormally rapid heartbeat that begins in the upper region of the heart and occurs sporadically. In adults the heartbeat can rise to between 150 and 250 beats per minute; in children it may go even higher. The person is aware of an uncomfortably rapid heartbeat and may experience feelings of anxiety and doom, shortness of breath, chest tightness, fainting, and dizziness and may appear pale.
A sporadically occurring arrhythmia with an atrial rate that is usually 160 to 200 beats per minute. It originates above the bundle of His, and typically appears on the surface electrocardiogram as a rapid, narrow-complex tachycardia. This relatively common arrhythmia may revert to sinus rhythm with rest, sedation, vagal maneuvers, or drug therapy.