ROCADE study: ROle of interatrial Connection Ablation in reentry Dynamics an in-silico Evaluation

Background and Aims: Interatrial connections (IACs) may act as pathways sustaining atrial fibrillation (AF), yet their role as ablation targets remains uncertain due to challenges in identifying IAC-dependent reentrant circuits. This study tracks reentrant activity along IACs, characterizes IAC-dependent reentries, and assesses the impact of in-silico IAC ablation on reentry maintenance.Methods: Six patient-specific biatrial bilayer models were reconstructed from CT and MRI-derived geometries, each incorporating four IACs: Bachmann's bundle, fossa ovalis, upper posterior, and coronary sinus. The Courtemanche ionic model was used to simulate mild (M) and severe (S) AF-related electrical remodeling, with fibrosis burden ranging from 9.0% (M) to 27.6% (S). Across the 12 models, 110 sustained reentries were induced, followed by circumferential pulmonary vein isolation. Fifteen IAC ablation strategies were tested at three different timings. Critical pathways along the six possible interatrial loops were quantified. Tachycardia cycle length (TCL) and phase singularity (PS) clusters were analyzed before and after IAC ablation.Results: Overall, 11.8% of reentries were IAC-dependent. Larger interatrial loops were the major contributors to critical pathway formation. IAC-dependent reentries exhibited more critical pathways, shorter TCL (194.2 vs 201.9ms; ΔTCL=7.65ms, p = 0.006), and more PS clusters in the RA body (8 [5-10] vs. 4 [2-6], p = 0.006). Ablation timing did not influence termination rates.Conclusion: We present the first framework to track reentrant activity along IACs. We identified IAC-dependent reentry characteristics that may guide patient stratification and targeted ablation strategies in clinical practice.