Multiple Accessory Pathways as Substrate for Duodromic Tachycardia

BACKGROUND: Atriofascicular pathways are uncommon bypass tracts (BTs) with decremental conduction properties. We report a case involving 2 tachycardia mechanisms sharing a common accessory pathway as the retrograde limb. CASE SUMMARY: A 42-year-old man had a narrow-complex, short-RP tachycardia and wide-complex tachycardia with left bundle branch morphology during emergency department visits. The electrocardiogram during sinus rhythm showed manifest ventricular pre-excitation. During the electrophysiology study, both tachycardias exhibited an identical retrograde atrial activation sequence and a negative HV interval during wide-complex tachycardia. After successful radiofrequency ablation of posteroseptal BT, ventriculoatrial dissociation occurred with ventricular pacing. Incremental atrial pacing revealed progressive pre-excitation with atrioventricular interval prolongation, suggesting conduction via an atriofascicular pathway. DISCUSSION: Multiple BTs can coexist in the same patient. These can serve as anterograde or retrograde limbs of tachycardia, with the other limb being the atrioventricular node or another accessory pathway. Targeted ablation of the critical pathway can render tachycardia noninducible even if the other pathway persists. TAKE-HOME MESSAGE: Atriofascicular pathways can coexist with typical BTs in the same patient and can cause duodromic tachycardia.