AF with WCT

A case sent by a friend for comment. Is this VT or SVT with aberrancy?

Image Case

The initial rhythm is atrial fribrilation (AF) followed by wide complex tachycardia with right bundle branch block (RBBB) morphology with superior axis.

Interpreting wide complex tachycardia (WCT) is a challenge if the intrinsic rhythm in atrial fibrillation (AF). In this case, it is a bit easy. First the presence of a fusion beat (red arrows) indicates that the WCT is ventricular tachyardia (VT). Fusion beat is depolarization of the ventricles both by an ectopic ventricular impulse and supraventricular impulse. This results in a QRS complex that is intermediated in morphology/shape between the sinus beat and the ectopic ventricular beat.

Another morphological characteristic that is obvious in this strip is the "rabbit ear" morphology in the V lead. A right bundle branch block morphology with the left R taller than the right (rabbit ear) indicates that the WCT is VT. This is part of the Wellens criteria of RBBB WCT VT.

aVR can also be used to determine if a WCT is VT or not. It is called the Vereckie algorithm. A dominant initial R is suggestive of VT as in this case.

Thus, based on those morphological criteria. This WCT is VT (nonsustained).

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