How a Topological Mindset May Offer Extra Control During Mapping and Ablation of Left-Sided Reentrant Atrial Tachycardia.

Reentry (macro or localized) is historically described as multiple pathways that are separated by barriers (either anatomic or functional) and involve active and passive loops (identified by electro-anatomic and entrainment mapping, EAM/ETM). Some reentrant atrial tachycardia (AT) cases are characterized by challenging activation patterns and unexpected ablation responses. A recent translational study, focusing on topology and the role of boundaries, suggests that thinking topology within EAM/ETM might offer extra control during mapping and ablation of reentrant AT. We aimed to propose and prospectively validate a workflow (EAM/ETM+TOP) in which we integrate topological thinking within an EAM/ETM workflow for mapping and ablation of left-sided (left atrium) AT. The integrated workflow was performed in 88 left atrium reentrant AT cases. After EAM/ETM, the number of loops and potential ablation strategy were verified against the number of critical and noncritical boundaries (critical boundary [CB], non-CB). Linear radiofrequency lesions were deployed to connect both CBs, preferably by one direct CB-CB line. EAM/ETM+TOP-based mapping was feasible in all cases and led to a diagnosis of a 2B topology with single-loop activation in 33 cases and a≥3B topology with dual-loop activation in 55 cases. In 87 out of 88 cases, subsequent ablation via a direct CB-CB approach (n=75), an indirect CB-non-CB-CB (n=9), or an indirect CB-non-CB-non-CB-CB approach (n=3) led to successful termination of AT. No unexpected changes in tachycardia cycle length occurred. After a median FU of 356 (IQR, 228-537) days, 16 patients experienced recurrence of AT (18%). Thinking topology within an EAM/ETM workflow may offer extra control during mapping and ablation of left-sided reentrant AT.