LAUSR

A 76-year-old male patient with a history of ischemic cardiomyopathy (left ventricular ejection fraction, LVEF 15%) presented with a 3-day history of shortness of breath, dizziness, and weakness. ECG revealed a wide complex tachycardia with a right bundle branch block pattern QRS complexwith spontaneous transitions in and out of a secondwide QRS morphology, which was reproduced during electrophysiological study (Figure 1). No baseline ECGwas available at initial presentation. What is themechanism of the tachycardia?