“Classical” Response in a Pre-excited Tachycardia

Abstract

A 24-year-old patient presented with history of recurrent palpitation and was diagnosed as wide QRS tachycardia which was cardioverted. The sinus rhythm ECG and the tachycardia ECG are shown in Figure 1. During the electrophysiological study, 2 morphologies of tachycardia were inducible, 1 with right bundle branch block (RBBB) morphology (Figure 2A) and another with left bundle branch block (LBBB) morphology (Figure 2B), which was her clinical tachycardia. The LBBB type wide QRS tachycardia was faster (Figure 2B). During the RBBB morphology tachycardia, ventricular entrainment showed a V–A–V response and a His refractory ventricular extrastimulation advanced the retrograde atrial activation, resetting the tachycardia. Figure 1. Twelve-lead electrocardiograms of the patient in sinus rhythm ( A ) and during clinical tachycardia ( B ). Figure 2. Surface leads I, III, and V1 and intracardiac electrograms from right atrium (HALO 1, 2 at lateral right atrium to HALO 17, 18), His bundle (His bundle distal [HBED] and His bundle middle [HBEm]), the coronary sinus (coronary sinus distal [CSD] and coronary sinus proximal [CSP]) and right ventricular apex (RVA). A , The orthodromic tachycardia with right bundle branch block aberrancy. B , The left bundle branch block tachycardia of shorter cycle length and long ventricular–His of 80 ms with the same retrograde eccentric atrial activation as in the initial tachycardia. The LBBB morphology tachycardia showed variation in cycle length with a constant Ventriculo–Atrial (VA) interval. Atrial entrainment did not change the QRS morphology or VA relationship. An early premature atrial extrastimulation from the lateral right atrium showed an interesting finding (Figure 3). Very late atrial extrastimulus from the same location did not advance the V without affecting the septal A. What are the mechanisms of the two tachycardia? Figure 3. Surface leads I, III, and V1 and intracardiac electrograms from right atrium (HALO 1, 2 at lateral right atrium to HALO …