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Approach to the diagnosis of wide QRS complex tachycardias

Leonard I Ganz, MD, FHRS, FACC
Section Editors
Peter J Zimetbaum, MD
Ary L Goldberger, MD
James Hoekstra, MD
Deputy Editor
Brian C Downey, MD, FACC


Tachycardias are broadly categorized based upon the width of the QRS complex on the electrocardiogram (ECG).

A narrow QRS complex (<120 msec) reflects rapid activation of the ventricles via the normal His-Purkinje system, which in turn suggests that the arrhythmia originates above or within the atrioventricular (AV) node (ie, a supraventricular tachycardia [SVT]).

A widened QRS (≥120 msec) occurs when ventricular activation is abnormally slow for one of the following reasons (see 'Causes of WCT' below):

The arrhythmia originates outside of the normal conduction system (ie, ventricular tachycardia [VT])

Abnormalities within the His-Purkinje system (ie, SVT with aberrancy)

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Literature review current through: Nov 2017. | This topic last updated: Oct 22, 2015.
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