Anatomically Consistent Substrate of Macro‐Reentrant Atrial Tachycardia After Senning Procedure: Insights From Two Cases

We report two adult male patients in their 30s who underwent multiple radiofrequency ablation procedures for atrial tachycardia decades after the Senning operation. High-resolution electroanatomic mapping revealed two consistent tachycardia mechanisms: (i) reentrant circuit localized to the systemic venous atrium, and (ii) cavotricuspid isthmus-dependent reentry spanning both atria. Despite complex anatomy, targeted ablation achieved durable rhythm control. These cases demonstrate reproducible arrhythmogenic substrates in the post-Senning population and support the utility of empirical substrate-based mapping in guiding ablation strategies for atrial tachyarrhythmias.