Introduction: Despite high-resolution mapping, ablation of atrial fibrillation (Afib) remains challenging. Areas of rapid cycle length during AF are often considered to be drivers of AF. A novel cycle length mapping algorithm (CLM) embedded in the Carto3 System now allows direct visualization of cycle length and cycle length standard deviation during atrial fibrillation. The aim of this study was to evaluate the impact of the novel CLM algorithm and its capabilities to improve termination rates in Afib ablation procedures.

Methods: Patients with persistent Afib (de-novo and redo PVI) were included into the study. AFib was mapped using the Carto3 System with CLM mapping algorithm. For cycle length (CL) and cycle length standard deviation (CLSD) mapping, the PentarayTM catheter was held stable at one site for 2.5 seconds. CL and CLSD  limits were manually adjusted to focus on high frequent (CL) and highly repetitive (CLSD) areas. Ablation strategy was PVI (incl. gap closing) first and consecutive ablation of CLM detected areas. If CLM areas were located near the PV circle, the PV circle was extended. 

Results: 14 patients (median age 70 (62/72) years, 18% females ) were included into the study. Creation of the CL maps was reproducible and straightforward. Areas with rapid CL were rarely associated with a low CLSD, therefore the ablation strategy was mainly driven by CL maps. Four patients (29%) terminated into sinus rhythm during ablation. In our experience, in those patients who terminated, distribution of the CL areas was demarcated more clearly. 

Conclusion: The CLM mapping algorithm enables intensive analysis of the atrial fibrillation substrate. In this limited experience the atrial fibrillation could be terminated in SR in 29%. Up to date, reproducibility and long term - outcome still needs to be evaluated.