Supraventricular tachycardia with cycle length variation and apparent VA dissociation: what is the mechanism?:

A 33-year-old woman was referred for an electrophysiologic study because of a documented supraventricular tachycardia.Stimulation from the RV-apex showed retrograde conduction over the bundle of His without any evidence of an accessory pathway. Programmed atrial stimulation with one extra stimulus revealed a dual atrioventricular (AV) nodal physiology. …