AbstractIntroductionIdentifying the critical isthmus region (CIR) of atrial re‐entry tachycardias (AT) is challenging. The Lumipoint® (LP) software, developed for the Rhythmia® mapping system, aims to facilitate the successful ablation of ATs by identifying the CIR.ObjectiveThe objective of this study was to evaluate the quality of LP regarding the percentage of arrhythmia‐relevant CIR in patients with atypical atrial flutter (AAF).MethodsIn this retrospective study, we analyzed 57 AAF forms. Electrical activity (EA) was mapped over tachycardia cycle length resulting in a two‐dimensional EA pattern. The hypothesis was that EA minima suggest potential CIRs with slow‐conduction‐zone.ResultsA total ofn= 33 patients were included, with the majority of patients being already preablated (69.7%). LP algorithm identified a mean of 2.4 EA minima and 4.4 suggested CIRs per AAF form. Overall, we observed a low probability of identifying only the relevant CIR (POR) at 12.3% but a high probability that at least one CIR is detected (PALO) at 98.2%. Detailed analysis revealed EA minima depth (≤20%) and width (>50 ms) as the best predictors of relevant CIRs. Wide minima occurred rarely (17.5%), while low minima were more frequently present (75.4%). Minima depth of EA ≤ 20% showed the best PALO/POR overall (95% and 60%, respectively). Analysis in recurrent AAF ablations (five patients) revealed that CIR in de novo AAF was already detected by LP during the index procedure.ConclusionThe LP algorithm provides an excellent PALO (98.2%), but poor POR (12.3%) to detect the CIR in AAF. POR improved by preselection of the lowest and widest EA minima. In addition, there might be the role of initial bystander CIRs becoming relevant for future AAFs.