Hidden Slow Conduction Ablation for Recurrent Atrial Fibrillation: Unmasking the Arrhythmogenic Substrate (Unmask-AF)

"Ablation of pulmonary veins reconnections plus the search and ablation of hidden slow conductions sites (HSC) in the left atrium.~HSC sites are defined as EGMs showing highly fragmented or double electrograms in response atrial triple extrastimulus, presenting normal or fractionated electrogram in the sinus rhythm.~After checking for PV's conduction breakthroughs, point-by point ablation targeting HSC-EGMs will be performed.~The end point for HSC+ ablation will be reached with loss of local capture at a given lesion, pacing from the ablation catheter at high output (10V·2ms)."

Each vein will be re-assessed by observing PV potentials along the PV ostia and by pacing from the distal bipole of the ablation catheter (10mA at 2ms) within the lesion set with failed capture of the left atrium. In case of PVs reconnection touch-up applications will be performed at the earliest potential site, identified by comparing far-field atrial EGM to near-field local EGM timing, until isolation will be achieved (entrance and exit block).