3:2 antegrade atrioventricular block with AV nodal reentrant tachycardia: What is the mechanism and where is the block?

摘要

A previously healthy 14-year-old girl presented with history of intermittent palpitations with event recorder tracings demonstrating a narrow complex regular tachycardia with heart rates in 280s. Baseline electrocardiogram and echocardiogram were normal. A diagnostic elec-trophysiologic study was performed under general anesthesia. Baseline intervals were normal including a normal His-ventricular (HV) interval of 36 ms. There was no evidence of pathologic infranodal block or prolongation of HV during rapid atrial pacing. Dual atrioventricular (AV) node physiology could be elicited with atrial extrastimulation and atrioventricular nodal reentrant tachycardia (AVNRT) could be easily and reproducibly induced with isoproterenol infusion and atrial burst pacing at the AV block cycle length.