Whether ultra-high density (UHD) contact mapping (Rhythmia) may be used to map activation of atrial fibrillation (AF) is unknown.

We sequentially mapped the left atrial (LA) activation during AF ablation (circumferential pulmonary vein isolation–CPVI, followed by defragmentation).

Time reference was an LA appendage (LAA) electrogram (EGM). Points were acquired with respiratory gating if reference, mapped EGM (10ms tolerance) and electrode location were stable. For fragmented EGM the timing of the surrounding area was used. In case of extremely low voltage (<0.01mV) or lack of local statistical coherence no colour-code was displayed (grey area). Circular propagation around single points were defined as organized rotating drivers (see Fig. 1).

AF was mapped in 17 patients (patients; 9 men, 68±5 y). LA maps (162±49ml, 30947±14061 EGM, 95±26 cm²) were acquired in 15.7±6.5minutes. In 70% of the cases, stable rotating drivers (mean 1.9, 1 to 5) with continuous activation in the centre were visualized. All patients had CPVI followed by ablation of the centre of rotational regions and at sites with fragmented bipolar EGM. After CPVI, LAA CL increased from 171±10 to 199±14ms (P=0.02). Termination of AF without electrical cardioversion was obtained in 62%.

Sequential UHD activation mapping of AF allows visualisation of areas of rotational activation that are always around a fragmented EGM and seem to be an appropriate target for ablation.