A group of cardiac arrhythmias in which the cardiac contractions are not initiated at the SINOATRIAL NODE. They include both atrial and ventricular premature beats, and are also known as extra or ectopic heartbeats. Their frequency is increased in heart diseases.

Synonyms: Extrasystoles, Cardiac Complexes, Premature, Premature Cardiac Complex, Premature Beat, Extrasystole, Premature Beats, Ectopic Heartbeat, Beats, Premature, Heartbeat, Ectopic, Premature Cardiac Complices, Ectopic Heartbeats, Heartbeats, Ectopic, Premature Cardiac Complexes, Cardiac Complex, Premature, Complexes, Premature Cardiac, Beat, Premature