A case of junctional ectopic tachycardia with demonstration of both HA and HV dissociation during tachycardia

Abstract

The most definitive evidence for a junctional source of tachycardia comes from the demonstration of both HA and HV dissociation during tachycardia. Introduction Junctional ectopic tachycardia (JET) is an unusual tachyarrhythmia most commonly encountered in infants and children. These are considered to have origins in the atrioventricular (AV) node or the upper His-Purkinje system (HPS). Langendorf and Pick reported accelerated narrow QRS in the pediatric population that was dissociated from the sinus P wave in 1954 based on surface electrocardiogram (ECG) recordings. However, they attributed these to suppression of the sinus node in conjunction with a mildly accelerated nodal rhythm in the presence of an inflammatory reaction. Langendorf and Mehlman also described premature junctional beats interfering with AV nodal conduction in 1947. The more modern definitions of JET typically involve tachyarrhythmia with rates well over 100 beats per minute. The electrophysiologic (EP) characteristics of JET in the pediatric population were first described by Garson and Gillette in 1979. Multiple subsequent reports have described JET, some of which were treated with ablation. Several EP features have been proposed as suggestive of JET. The most suggestive one is a narrow QRS tachycardia with AV dissociation and a His bundle electrogram preceding each QRS complex. On EP testing, the HA intervals during junctional tachycardia tend to be longer than during typical atrioventricular nodal reentrant tachycardia (AVNRT) and may be closer to the HA interval during ventricular pacing. Similarly, an AH-HA response to atrial overdrive pacing is typically observed in JET, as the return beat following cessation of pacing is characterized by an HA sequence. Furthermore, a late-coupled premature atrial complex delivered