Supraventricular tachycardia following slow pathway ablation: What is the mechanism?

The article presents a case study of a 72-year-old woman who underwent a diagnostic three-wire electrophysiology study. The woman had a history of tachycardia with left bundle branch block (LBBB) morphology, and after a pathway modification, she developed an incessant tachycardia (TCL). The woman's Atrial-His-His Atrial (AHHA) response measurement demonstrates the link of the first His after atrial pacing termination to the penultimate beat in the drive train rather than the final beat.