extrasystole

extrasystole A premature contraction of the heart that is independent of the normal rhythm of the heart. An extrasystole begins in a part of the heart other than the normal heartbeat origin, the sinoatrial (SA) node. Extrasystoles are followed by a pause, as the heart electrical system “resets” itself, and the contraction following the pause is usually more forceful than normal. These more forceful contractions can be perceived as palpitations. See also palpitations.