Abstract Body (Do not enter title and authors here): Background: Catheter ablation (CA) for atrial fibrillation (AF) in patients with heart failure (HF) reduces mortality and hospitalizations and improves ejection fraction (EF). Arrhythmia-induced cardiomyopathy (AIC) is diagnosed after complete resolution of HF following AF ablation.

Aim: We aim to identify the prevalence and pre-ablation predictors value of AIC among patients with persistent AF and HF enrolled in the DECAAF II trial.

Methods: We utilized the DECAAF II database, where 815 patients with persistent AF underwent late-gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR) before and three-months after receiving CA for AF. Patients were randomized to receive pulmonary vein isolation (PVI) in addition to substrate modification (SM) or standard PVI alone. Ejection fraction was collected before, and three months after CA. Patients were asked to submit a single-lead ECG every day or when feeling symptoms using a single-lead handheld ECG device. AF Burden was defined as the percentage of monitored time spent in AF. For this analysis, we only included patients diagnosed with HF with available LV function data before and after CA. We defined AIC as HF and AF patients who experience EF improvement to ≥50% after ablation, with at least 10% improvement in EF.

Results: We identified 119 patients with HF and persistent AF; 72 (60.5%) fulfilled criteria for AIC, and 47 (39.5%) were non-AIC patients[SC1] . At baseline, AIC patients had an LVEF of 39.1±7.9, non-AIC had 39.2±7.9 (p=0.9). There was no difference between the two groups in baseline characteristics, AF burden [SC2] or AF recurrence (Table). The distribution of fibrosis from LGE-CMR prior to ablation was the only significant pre-ablation predictor of AIC among patients with HF and persistent AF. Patients with AIC had significantly lower percentage of fibrosis in the septal wall compared with non-AIC patients (12.2±10 vs 20.7±11.4, p <0.001), regardless of the total amount of LA fibrosis.

Conclusion: In this post-hoc analysis of the DECAAF II trial, we found that up to 60% of patients with HF and persistent AF have AIC rather than primary cardiomyopathy. We also described LGE-MRI as a significant differentiator between AIC and other cardiomyopathies complicated with arrhythmia.