Coincident Atrioventricular Nodal Reentrant and Idiopathic Left Ventrirular Double Tahycardias: Unique Electrophysiological Properties Related to Longituginal Dissociation of His Bundle

Abstract

Co-existence of idiopathic left fascicular ventricular tachycardia with other arrhythmias is very rare. Here we report the case of an 11-year-old boy who presented with a history of palpitations on exercise. His ECG during treadmill stress test showed narrow QRS tachycardia with right bundle branch block and left axis morphology. Electrophysiological studies revealed two inducible tachycardias: idiopachic left ventricular tachycardia originating from the posterior fascicles and slow-fast atrioventricular nodal reentrant tachycardia. Idiopathic left ventricular tachycardia was induced by right and left ventricular stimulation. On the other hand, atrioventricular nodal reentrant tachycardia was not inducible by right atrial and ventricular stimulation, however, it was inducible by left ventricular stimulation and trrigered by left posterior fascicular arrhythmia. We speculated that the presentation of an unusual form of slow-fast atrioventricular nodal reentrant tachycardia induction was conceptually related to the property of functional longitudinal dissociation within the His bundle, i.e., left Purkinje fibers activation was conducted earliest to the atrioventricular nodal fast pathway. Radiofrequency catheter ablation for both tachyarrhythmia was performed at two consecutive sessions successfully.