Ablation of "Background Tachycardia" in Long Standing Atrial Fibrillation: Improving the Outcomes by Unmasking a Residual Atrial Fibrillation Perpetuator

Catheter ablation of long-standing persistent AF (LSAF) remains challenging. Since AF-Nest (AFN) description, we have observed that a stable, protected, fast source firing, namely "Background Tachycardia"(BT), could be hidden beneath the chaotic AF. Following pulmonary vein isolation (PVI)+AFN ablation one or more BT may arise or be induced in 30-40% of patients, which could be the culprit forAF maintenance and ablation recurrences. We studied 114 patients, from 322 sequential LSAF regular ablations, having spontaneous or induced residual BT after EGM-guided PVI+AFN ablation of LSAF; 55.6±11y/o, 97males (85.1%), EF=65.5±8%, LA=42.8±6.7mm. Macroreentrant tachycardias were excluded. Pre-ablationAF 12-leads ECG Digital processing(DP) and spectral analysis(SA) was performed searching for BT before AF ablation and its correlation with BT during ablation.After PVI, 38.1±9 AFN sites/patient and 135 sustained BTs (1-3, 1.2±0.5/patient) were ablated. BT cycle length(CL) was 246.3±37.3ms. In 79 patients presenting suitable DP for SA, the BT-CL was 241.6±34.3ms with intra procedure BT-CL correlation r=0.83/p