Aberrant conduction
Also calledaberrancy · aberrantly conducted beat · rate-related bundle branch block · functional bundle branch block
Definition
Abnormal conduction of a supraventricular impulse through the ventricular conduction system, producing a QRS complex whose shape differs from the baseline QRS (often wide) and may resemble a bundle branch block pattern, a fascicular block pattern, or both, despite the supraventricular origin. It can occur when an impulse arrives early, while part of the conduction system is still refractory, classically one that ends a long-short RR sequence (the Ashman phenomenon). Because the right bundle branch has a longer refractory period than the left, aberrancy takes a right bundle branch block pattern more often. Telling aberrant conduction apart from ventricular ectopy is a central question when reading wide-QRS beats and tachycardias.
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
- Chenevert M, Lewis RJ. Ashman's phenomenon: a source of nonsustained wide-complex tachycardia. J Emerg Med. 1992;10(2):179-183. doi.org/10.1016/0736-4679(92)90213-d
- Wellens HJ, Bär FW, Lie KI. The value of the electrocardiogram in the differential diagnosis of a tachycardia with a widened QRS complex. Am J Med. 1978;64(1):27-33. doi.org/10.1016/0002-9343(78)90176-6
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.