Response: The rhythm strip illustrates the induction of tachycardia, following an aberrantly conducted through the left bundle branch beat, the morphology of which was consistent with the aberrancy. The electrocardiogram shows conduction alternans. The morphology of the tachycardia and the conduction disturbance suggest bundle branch reentry ventricular tachycardia, which was demonstrated in the electrophysiological study (Figure 1).

Figure 1

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