Harder Roads to Trek? Paradoxical Slowing of an Atrioventricular Reentrant Tachycardia With Contralateral Bundle Branch Block
A 36‐year‐old male was subjected to electrophysiological (EP) study and ablation of manifest ventricular pre‐excitation and palpitations related to supraventricular tachycardia. Baseline ECG demonstrated features of anterospetal pre‐excitation. While mapping the tricuspid annulus, tachycardia was induced that demonstrated a left bundle branch block morphology (LBBB). This morphology changed to a right bundle branch block (RBBB) with which the tachycardia cycle length decreased by 20 milliseconds (Fig. 1).