Dissociation between anterograde and retrograde conduction during transvenous cryoablation of parahissian accessory pathways.

Ablation of parahissian accessory pathways (APs) is a challenging procedure because of the high risk to provoke "iatrogenic" atrioventricular (AV) nodal block. The feasibility and safety of cryoablation (CA) have been already demonstrated both in patients with AV nodal reentry tachycardia and in those with anteroseptal APs. However, dissociation between anterograde and retrograde conduction after CA has not yet been described. We report two cases of CA of parahissian AP associated with transient dissociation between anterograde and retrograde conduction.