Review Figure 1: Wide QRS Complex Tachycardia
The American Heart Hospital Journal the absence of retrograde conduction.16 Even though
capture and fusion beats are not frequently observed, their presence suggests VT.
Comparison with the baseline ECG is an important part of the process. A change in the QRS complex morphology or axis by more than 40°, as well as a QRS axis of -90° to -180° suggests a ventricular origin of the arrhythmia.17,18
An
entirely positive QRS complex in lead augmented ventor left (aVR) also supports the diagnosis of VT.17
When the
sinus rhythm with wide QRS becomes narrow with a tachycardia, this indicates VT.19
The morphology of a
Wide QRS complex tachycardia at 102 bpm. The tracing has an initial R wave in lead augmented vector right (aVR) which points towards ventricular tachycardia (VT). This patient had amiodarone-induced VT. aVF = augmented vector foot; aVL = augmented vector left. Vereckei et al.29
tachycardia similar to that of premature ventricular contractions seen on prior ECGs increases the probability of a ventricular origin of the arrhythmia.
One approach to the interpretation of wide QRS complex tachycardias is to divide them into right bundle branch block morphology (QRS complex being predominantly
Figure 2: Wide QRS Complex Tachycardia
positive in lead V1) and left bundle branch block morphology (QRS complex being predominantly negative in lead V1).20
Wide complex tachycardias with right bundle branch block morphologies are more likely to be of ventricular origin in the presence of the following criteria:
• QRS complex duration of more than 140 ms; • the presence of positive concordance in the precordial leads;
• a superior axis of the QRS complex; • the presence of a qR, R or RS complex or an RSR’ complex where R is taller than R’ and S passes through the baseline in V1; and
• an R to S ratio of more than one in V6.4,20–22
Wide QRS complex tachycardia at 198 bpm. An R to S interval of more than 100 ms points towards a ventricular origin of the tachycardia by the Brugada criteria.24
aVF = augmented vector foot; aVL = augmented vector left; aVR = augmented vector right.
Left bundle branch block morphology tachycardias are more likely to be VT if they have the following features:
• QRS complex duration of more than 160 ms; • the presence of negative concordance in the precordial leads;
Medications should be carefully reviewed. Vaugham Williams Class I and Class III antiarrhythmic medications, multiple medications that prolong the QT, and digoxin at toxic levels may cause VT.
The Electrocardiogram
A careful review of the electrocardiogram (ECG) may provide clues to the origin of a wide QRS complex tachycardia. The presence of atrioventricular dissociation strongly favors the diagnosis of VT. However, it may also be observed in atrioventricular junctional tachycardia in
34 Approach to the Differentiation of Wide QRS Complex Tachycardias
• the presence of an rS complex in V1; and • mostly negative QS complex in V6.4,20–22
In addition to these criteria, the presence of an R wave of more than 30 ms duration, notching of the downstroke of the S wave, or duration from the onset of the QRS to
the nadir of the S wave in leads V1 or V2 of greater than 60 ms and any Q wave in lead V6 favors the ventricular origin of an arrhythmia.23
It consisted A protocol for the
differentiation of a regular, wide QRS complex tachycardia was published by Brugada et al.24 of four diagnostic criteria:
Summer 2011
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