Ablation of Atrioventricular nodal “slow pathway” for simultaneous treatment of coexisting atrioventricular and nodal reciprocating tachycardias

Abstract

We report the case of a 49-year-old male patient with recurrent palpitations and two different supraventricular reciprocating tachycardias due to atrioventricular (AV) nodal reentry and orthodromic AV reentry sustained by a left-sided, concealed AV accessory pathway (AP). During the baseline electrophysiological study, dual AV nodal conduction (90 ms jump) 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. In both cases, shift and sustained conduction over the AV "slow pathway" were required for tachycardia induction and maintenance, 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 a continuous AV nodal conduction curve, persistent conduction over the AP, and only single orthodromic AV echo beat 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 4 years follow-up the patient is still asymptomatic without antiarrhythmic drug usage. 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 could be considered, under some instances (e.g. right antero-septal accessory pathways, older patients, etc), in order to reduce the procedure risks due to multiple arrhythmia substrate ablations.