AV block
Also calledatrioventricular block · AVB · heart block · AV conduction block
Definition
A delay or failure of conduction of atrial impulses to the ventricles, which can occur in the AV node, within the His bundle, or below it. It is graded as first-degree (every P wave conducts, but with a PR interval over 200 ms, so it is more accurately a delay than a block), second-degree (some P waves fail to conduct), or third-degree, also called complete heart block (no conduction from atria to ventricles). Block in the AV node usually carries a better prognosis than block within or below the His bundle.
Clinical noteBlock within or below the His bundle can progress rapidly and unexpectedly and is associated with a slower, less predictable ventricular escape rhythm, whereas AV nodal block progresses more slowly and has a faster, more reliable junctional escape rhythm.
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
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.