High-grade AV block
Also calledadvanced AV block · high-degree AV block · advanced second-degree AV block · high-grade second-degree AV block
Definition
An advanced form of second-degree AV block in which two or more consecutive P waves, occurring at a constant physiologic atrial rate, fail to conduct while some P waves still do conduct (for example 3:1 or 4:1 conduction), distinguishing it from complete block, where none conduct. Because the definition requires P waves at a normal rate, non-conduction caused only by a fast atrial rate does not count. It is generally considered to lie within or below the His bundle, where block can progress rapidly and unexpectedly, although in some cases the block is in the AV node.
Clinical noteConduction of at least some P waves separates it from complete (third-degree) block, where none conduct.
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
- Barold SS, Herweg B. Mobitz type II second-degree atrioventricular block: a commonly overdiagnosed and misinterpreted arrhythmia. Front Cardiovasc Med. 2024;11:1450705. doi.org/10.3389/fcvm.2024.1450705
- 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
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.