Trompe l’oeil electrocardiogram

Given the QRS width, the intraventricular conduction delay could not be explained solely by the left anterior hemiblock (LAHB). Placement of the rightward precordial leads V1–V2 one intercostal (IC) space above the conventional level uncovered a terminal R-wave suggestive of complete right bundle branch block (RBBB) (Fig. 1). Although there might be a contributing role for delayed activation of the anterobasal left ventricle wall in explaining this R’ wave (not determined), the electrophysiological study was in favour of a proximal RBBB (QRS to right ventricle apex interval of 36ms), and showed a high risk for atrioventricular block: baseline His-ventricular interval of 57ms, prolonging to 102ms with some infra-Hisian blocked atrial pacing beats (CL 420ms) under ajmaline. No structural or ischaemic heart disease was revealed. Considering these findings, the use of a class Ic antiarrhythmic drug was most likely the cause of the paroxysmal atrioventricular block in our patient. An implantable loop recorder could have been considered in our patient as propafenone had already been stopped, but we decided to give prophylactic double chamber pacing therapy. There was no recurrence of brady-symptomatology during follow-up, but palpitations were still noted with episodes of paroxysmal atrial fibrillation seen in the memory of the device, for which ablation therapy was provided.