Intracardiac and surface ECG recordings during electrophysiologic study of bundle branch reentrant ventricular tachycardia

Shown are five surface ECG leads (I, II, aVF, V1, V6) and intracardiac recordings from the high right atrium (HRA3-4), His bundle region (HBE1-2), and the right ventricular apex (RVA3-4). The atrial and ventricular (V) electrograms are dissociated, confirming a ventricular tachycardia; however, a His bundle depolarization (H) precedes each ventricular electrogram. Further testing confirmed the diagnosis of bundle branch reentrant ventricular tachycardia (BBRVT), a macroreentrant ventricular tachycardia involving the left and right bundle branches. During typical BBRVT, the wavefront goes down the right bundle, across the interventricular septum, and then retrograde up the left bundle, with passive retrograde activation of the His bundle. Since both bundle branches are necessary parts of the macroreentry circuit, catheter ablation of the right bundle branch is curative.