“…A), which indicates that a slow AV nodal pathway is acting as the antegrade limb of the tachycardia and supports the diagnosis of AVNRT. As AV nodal slow pathway is not involved in JET, advancement or delay of the next His signal via extrastimuli (or spontaneous atrial ectopic beats) timed to His refractoriness is not possible in this tachycardia, although spontaneous cycle length changes may mimic this phenomenon.…”