Outcomes of atypical flutter ablation exclusively guided by systematic analysis of high-resolution maps (no entrainment maneuvers)

Abstract Introduction Advancements in high-density mapping systems have enhanced our understanding of atypical flutters (AFl) mechanisms. However, a systematic analysis of substrate and activation maps is crucial for accurate arrythmia interpretation and design a targeted ablation strategy. Purpose To evaluate the acute and long-term success of left-sided AFl ablation. Methods Single-center retrospective study of left-sided AFl patients (pts) submitted to a high-density mapping and ablation from 2015 to June 2024. Map collection and interpretation were performed in a step-by-step and systematic manner, aiming to understand the AFL mechanism and plan the ablation lines to target the critical isthmus, without resorting to entrainment maneuvers. If AFl persisted after the 1st ablation set, a remap was performed to characterize the arrythmia mechanism. Acute success was defined as conversion to sinus rhythm with the planned ablation set. The procedure endpoint was the demonstration of conduction block in a remap during pacing close to the ablation line. Arrhythmic relapse was defined as any atrial arrhythmia recurrence. Results A total of 128 pts were included (58% male, 68±11 years old). Around 52% were submitted to a prior pulmonary vein isolation, with an additional left atrial linear ablation in 16% (n=20). Concerning arrythmia mechanistic, a macrorrentrant circuit was observed in 84% of the patients (fig 1) with perimitral loop being the most frequent reentrant circuit (N=51, 56%). In perimitral flutters with an additional loop, an even distribution rotating around the PV was observed (left PV, n=19; right PV = 18). The 1st set of mechanism-tailored ablation restored sinus rhythm in 81 pts (63%) (fig 1). After remap, the following AFl mechanism were observed: (1) same AFl using a gap in ablation line in 8 pts; (2) same AFl using a loop previously not recognized in 3 pt; (3) a completely different left-sided AFl with a distinctive circuit (N=27); or (4) a right-sided peri-tricuspid flutter in 9 pts. Completion of the ablation set resulted in sinus rhythm restoration in 37 of these 47 pts, resulting in an overall acute success rate of 92% (118/128). After a single procedure, the 1-year success rate was 76%, decreasing to 51% at 3-years. After additional redo procedures, freedom from arrhythmia recurrence increased to 81% at 1 year and 58% at 3 years – figure 2. During a mean follow-up 3±2 years, 22 pts were submitted to a redo procedure, consisting in typical AFl ablation in 3, PVI isolation in 1, focal AT in 1 and atypical AFl redo in 17 pts. In 10 pts (7.8%) AV nodal ablation was performed due to persistent arrhythmia. Conclusion Left sided AFL ablation, based on a systematic mapping approach to understand arrhythmia mechanisms, leads to a high acute success with acceptable long-term results.