Case Report of Atrio-Ventricular Reentry Tachycardia Due to Accessory Pathway Having Unidirectional Anterograde Conduction Block and Typical Atrio-Ventricular Nodal Reentry Tachycardia Both Clinically Cured by Ablation of the Only Atrio-Ventricular Nodal “Slow Pathway”

Abstract

Introduction We report the case of a 49-year old male patient with recurrent palpitations and 2 different supraventricular tachycardias due to atrio-ventricular (AV) nodal reentry and orthodromic AV reentry sustained by a left-sided, unidirectional, AV accessory pathway (AP) evidenced during electrophysiological study. Method and Results During the baseline electrophysiological study, dual AV nodal conduction (90 ms A2H2 sudden jump at 320 ms A1A2 coupling interval), and non-decremental, eccentric, ventriculo-atrial conduction due to a left-sided, unidirectional, postero-septal AP were documented. Both typical AV nodal reentrant and orthodromic AV reentrant tachycardias were induced by programmed electrical stimulation several times. Intervals measured during each tachycardia are reported in the Table. The diagnosis of tachycardia mechanism was performed according to standard criteria. In both cases, shift and sustained conduction over the AV “slow pathway” were required for tachycardia inductions and maintenances, respectively. Accordingly, catheter ablation was performed by targeting the AV nodal “slow pathway” first with radiofrequency current applications delivered at the inferior portion of the Koch's triangle. Irritative, slow-rate junctional rhythm was observed during ablation. Afterward, programmed electrical stimulation demonstrated continuous AV nodal conduction curve, persistent conduction over the AP, and only single orthodromic AV echo beats inducible under baseline condition and pharmacological stress (atropine 0.02 mg/kg i.v. bolus and continuous isoprenaline i.v. administration). Sustained reentrant tachycardias were not inducible any more. For these reasons, the procedure was stopped without any attempt to ablate the AP. After a 18 month follow-up the patient is still asymptomatic without antiarrhythmic drug usage. Conclusion AV nodal “slow pathway” ablation may abolish both typical AV nodal reentry tachycardia and orthodromic AV reentry tachycardia induction when the latter arrhythmia is dependent from AV nodal “slow pathway” conduction for induction and maintenance. This ablation strategy resulted in a mid-term clinical success in the reported case, and it could be considered, under some instances (i.e. right antero-septal accessory pathways, older patients, etc), in order to reduce the procedure risks due to multiple arrhytmia substrates. ![Graphic][1] [1]: /embed/graphic-1.gif