Discussion
Whether patients returning after index PVI with new atypical AFL represent an attractive target for redo ablation has not been the subject of rigorous investigation. We sought to investigate the rates of arrhythmia-free 1y survival in two cohorts of patients presenting with recurrent arrhythmia following PVI: those with atypical AFL only, and those with recurrent AF (with or without flutter). The main findings of our study are: 1) Patients undergoing repeat ablation for atypical AFL after index AF ablation have enlarged LA and higher LAVi; 2) Use of RF energy in the index AF ablation is higher among patients developing recurrent atypical AFL; 3) Isolated roof dependent AFL and peri-mitral AFL account for roughly 60% for post-PVI flutters observed; 4) 1-year arrhythmia free survival rate is higher among patients undergoing repeat ablation for atypical AFL as compared to recurrent AF.
We found that LA diameter and LA volume was significantly greater among patients developing atypical AFL as compared to AF after the index ablation. This finding is in line with previous studies which reported that greater LA diameter(4) and LAVi(5) independently predict de novo atypical AFL, highlighting the role of intrinsic structural alteration in mediating fixed reentry.
We also observed that the use of RF energy for index ablation was significantly higher among the patients developing recurrent atypical AFL as compared to recurrent AF. A number of previous studies have reported the factors predictive of atypical AFL recurrence after AF ablation(6-8), and few of the studies(9,10) evaluated the predictive value of energy source (RF vs. cryo) during AF ablation. Julia et al (9); reported in their study that RF AF ablation is associated with a higher incidence of recurrent atypical AFL as compared to CB AF ablation. However, on adjusted analysis to determine the predictors of atypical AFL, the predictive value of RF ablation was attenuated. Although we did not have further data related to index AF ablation to perform an adjusted predictor analysis, our study with a large sample size is important in suggesting that CB ablation of AF may be associated with a lower incidence of atypical AFL recurrence as compared to RF ablation. Similar to several other previously published studies(6,11-13), Our study suggests that roof dependent and perimitral atypical atrial flutters are common in pre ablated patients. Our results derived from a large sample size extend the support to the hypothesis that previous AF ablation predisposes to the development of perimitral and roof dependent flutter forms.
To the best of our knowledge, our study is the first with a relatively large sample size to evaluate the prognostic significance of recurrent atypical AFL after index AF ablation on the success of the repeat ablation. Ammar et al (14), in their small retrospective study, showed that recurrent atrial tachycardia after PsAF ablation is associated with a better success rate of repeat ablation procedure compared to recurrent persistent AF. In contrast, our study included both types of AF patients at the time of index ablation and comprised a greater proportion of PAF patients than PsAF patients. Additionally, we also demonstrated that patients undergoing repeat ablation for atypical AFL were older with dilated LA and higher LAVi compared to those presenting with recurrent AF; these factors are associated with poor ablation outcomes. Our results are interesting in demonstrating that despite the association with factors predictive of poor outcomes of the ablation procedure, patients undergoing repeat ablation for atypical AFL have a better success rate as compared to those for recurrent AF.
The findings of our study should be interpreted with attention to the associated limitations, including: 1) Limitations inherent to a single-center, retrospective, and observational study; 2) We did not have detailed data related to index AF ablation for all patients, precluding an adjusted analysis to determine predictive factors for atypical AFL recurrence; 3) LA diameter and LA volume were not available for all the included patients; 4) lack of continuous ECG monitoring during follow-up might have contributed to an underestimation of arrhythmia recurrence rate.
In conclusion, based on our experience, roof dependent, and perimitral flutter are the common forms of atypical AFL after index AF ablation. Patients developing atypical AFl after index AF ablation have dilated LA and higher LAVi and arrhythmia free survival rate of first repeat ablation is higher for patients presenting with recurrent atypical AFL as compared to recurrent AF.