Separate Electrograms and Morphologically Distinct QRS Complexes During Ventricular Tachycardia: Critical Versus Noncritical Isthmus.

The electrogram morphology and its timing within the ventricular tachycardia (VT) cycle enable electrophysiologists to infer the location of the scar and its relationship to the VT circuit. This becomes particularly important in the presence of double-entrance or double-exit configurations, where distinguishing the critical isthmus from a noncritical bystander is essential.