Electrophysiology of postinfarction ventricular tachycardia: A paradigm ofstable reentry

Point of View. sustained monomorphic ventricular tachycardia (VT) is a para digm of a stable reentrant rhythm. The hallmark of stable reentry is the pr esence of an excitable gap, which in reentrant VT composes 15% to 45% of th e tachycardia cycle length. Resetting allows definition of the extent and p attern of the excitable gap. Site-specific resetting responses suggest that the VT circuit has both functionally and anatomically derived characterist ics. Entrainment provides information regarding the effects of overdrive pa cing on properties of the tissue composing the circuit rather than on prope rties of the tachycardia itself, These data help us to understand the mecha nisms of pharmacologic agents and to direct ablation of reentrant VT.