Sinoatrial exit block
Also calledSA block · SA exit block · sinoatrial block · sinoatrial exit block
Definition
A conduction failure between the sinoatrial node and the atrium: the sinus impulse is generated but cannot leave the node, so the atria are not activated and a P wave (with its QRS-T) drops out. In type II SA exit block the P-P intervals do not change before the block and the pause is a whole-number multiple (usually twice) of the baseline P-P interval, which distinguishes it from a sinus pause. In type I (Wenckebach) the P-P intervals shorten progressively before the dropped P wave, producing group beating, and the pause is not a whole-number multiple of the basic P-P interval.
Clinical noteGroup beating with progressively shortening P-P intervals suggests type I; a pause that is an exact multiple of the P-P interval suggests type II.
Sources
- Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay. Circulation. 2019;140(8):e382-e482. doi.org/10.1161/CIR.0000000000000628
- Mason JW, Hancock EW, Gettes LS. Recommendations for the standardization and interpretation of the electrocardiogram: Part II: electrocardiography diagnostic statement list. Circulation. 2007;115(10):1325-1332. doi.org/10.1161/CIRCULATIONAHA.106.180201
- 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
- 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
- Alomari L, Adebolu O, Idowu A, Khraisha O. The subtle pattern of sinoatrial Wenckebach. JACC Case Rep. 2026;31(6):106348. doi.org/10.1016/j.jaccas.2025.106348
- Da Costa D, Brady WJ, Edhouse J. ABC of clinical electrocardiography: bradycardias and atrioventricular conduction block. BMJ. 2002;324(7336):535-538. doi.org/10.1136/bmj.324.7336.535
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.