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Clinical manifestations, diagnosis, and evaluation of narrow QRS complex tachycardias

Leonard I Ganz, MD, FHRS, FACC
Section Editors
Bradley P Knight, MD, FACC
Ary L Goldberger, MD
James Hoekstra, MD
Deputy Editor
Brian C Downey, MD, FACC


Tachyarrhythmias, defined as abnormal heart rhythms with a ventricular rate of 100 or more beats per minute, can result from a variety of pathologies and are frequently symptomatic. Signs and symptoms related to the tachyarrhythmia most commonly include palpitations or chest discomfort, but may also include shock, hypotension, heart failure, shortness of breath, and/or decreased level of consciousness. Symptoms can sometimes may be more subtle and may include fatigue, lightheadedness, or exercise intolerance. Some patients are truly asymptomatic; this may be more common in nonparoxysmal (incessant) tachycardias.

This topic will provide a broad overview of the different causes of narrow QRS complex tachycardia and an approach to their evaluation and diagnosis. An overview of the acute management of tachyarrhythmias, along with detailed discussions of specific narrow complex tachycardias (eg, AVNRT, AVRT, and AT) and a broad discussion of wide complex tachycardias, are presented separately. (See "Overview of the acute management of tachyarrhythmias" and "Atrioventricular nodal reentrant tachycardia" and "Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway" and "Focal atrial tachycardia" and "Approach to the diagnosis of wide QRS complex tachycardias" and "Approach to the management of wide QRS complex tachycardias".)


Tachycardias, with a ventricular heart rate exceeding 100 beats per minutes, are broadly categorized based upon the width of the QRS complex on the electrocardiogram (ECG) [1].

A narrow QRS complex (<120 milliseconds) reflects rapid activation of the ventricles via the normal His-Purkinje system, which in turn suggests that the arrhythmia originates above or within the His bundle (ie, a supraventricular tachycardia). The site of origin may be in the sinus node, the atria, the atrioventricular (AV) node, the His bundle, or some combination of these sites.

A widened QRS (≥120 milliseconds) occurs when ventricular activation is abnormally slow. The most common reason that a QRS is widened is because the arrhythmia originates below the His bundle in the bundle branches, Purkinje fibers, or ventricular myocardium (eg, ventricular tachycardia). Alternatively, a supraventricular arrhythmia can produce a widened QRS if there are either pre-existing or rate-related abnormalities within the His-Purkinje system (eg, supraventricular tachycardia with aberrancy), or if conduction occurs over an accessory pathway. Thus, wide QRS complex tachycardias may be either supraventricular or ventricular in origin. (See "Approach to the diagnosis of wide QRS complex tachycardias".)

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Literature review current through: Nov 2017. | This topic last updated: Sep 28, 2016.
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