Ectopic beat
Also calledectopic · extrasystole · premature beat · premature complex · ectopy
Definition
A beat that originates from a focus outside the sinoatrial node (atrial, junctional or ventricular tissue). An ectopic beat that arrives earlier than the next expected sinus beat is a premature beat (extrasystole); a late beat from such a focus that ends a pause is instead called an escape beat. Morphology depends on origin: a premature atrial complex has an early P wave whose shape differs from the sinus P wave, followed by a QRS like the normal beats unless it is conducted aberrantly, whereas a premature ventricular complex usually has a wide QRS (over 120 ms) of abnormal shape with no preceding P wave. Mechanisms include enhanced or abnormal automaticity, triggered activity and reentry.
Sources
- Samesima N, God EG, Kruse JCL, et al. Brazilian Society of Cardiology guidelines on the analysis and issuance of electrocardiographic reports - 2022. Arq Bras Cardiol. 2022;119(4):638-680. doi.org/10.36660/abc.20220623
- Al-Khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Circulation. 2018;138(13):e272-e391. doi.org/10.1161/CIR.0000000000000549
- Antzelevitch C, Burashnikov A. Overview of basic mechanisms of cardiac arrhythmia. Card Electrophysiol Clin. 2011;3(1):23-45. doi.org/10.1016/j.ccep.2010.10.012
- Viljoen C, Smith R, Chin A. Reviewing the causes of electrocardiographic pauses. Cardiovasc J Afr. 2017;28(4):257-260. doi.org/10.5830/CVJA-2017-041
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.