Fehmi Keçe

Left Atrial Box Surface Ratio and AF-Recurrence 175 8 AF and heart failure (29). Two-years follow up demonstrated 70% freedom from AF/AT off antiarrhythmic drugs. This is a very respectable outcome considering that heart failure patients with persistent atrial fibrillation are at high-risk for recurrence of AF (30). It may be reasoned that the extensive box lesion performed in this study explains the high success rate in these patients with heart failure and persistent atrial fibrillation. 8.4.5 Limitations The present study is a single-centre, retrospective study in a small group of patients. Due to the small group of patients this study may have been underpowered to detect other parameters influencing arrhythmia recurrence. Therefore, this study should be considered as ‘hypothesis generating’. Several prior studies already have presented data on the value of isolating the posterior wall, however the aim of this study was not to evaluate the value of posterior wall isolation, but the influence of the size of the ablated anatomical box lesion surface area as a ratio of total left atrial surface area on the outcome of this procedure. Our study did not show that extending the inferior line between the inferior poles of the inferior pulmonary veins improved outcome. Further larger and randomised studies need to confirm that a relatively larger box lesion or extension of the box lesion inferior from the inferior ostia of the PV’s protects against arrhythmia recurrence. In the study population 56% had undergone a prior PVI, which can have influenced the results. However, this was not significantly different between the groups. During the index-procedure in 10 patients (14%) additional ablation was performed, this was however not significantly different between the groups. Moreover, when these 10 patients were excluded from the analysis, the study results remained unchanged. Only repeated 24h Holter monitoring was used during follow-up. Therefore, asymptomatic AF episodes may have been missed. The recurrence group had more often LA enlargement compared to the no-recurrence group. However, this number was not significant in multivariate analysis. During the procedure durable isolation of the pulmonary veins and box lesion was not enhanced using manoeuvres such as the pace/ablate method (31) or adenosine infusion, which could have improved outcomes in both groups. No atrial substrate analysis was performed in this study. Distinguishing the presence of fibrotic areas based on MRI findings and/or high resolution voltage mapping and comparing the posterior LA with other LA regions could be helpful. Despite the limitations, we believe that this study is an important scientific contribution with potentially valuable suggestions for further research. Box lesion surface ratio is a new parameter to predict outcome in persistent AF ablation and we think that our hypothesis-generating study will trigger new research on extending the box lesion in patients with a small box lesion surface ratio to improve outcome.