4.5 NPAs with a greater AWT
A previous study provided simultaneous endo-epicardial high-density mapping data of breakthroughs during AF and demonstrated that the large majority of breakthroughs are explainable by transmural conduction.19 Recently, Parameswaran et al. analyzed simultaneously acquired endo-epicardial right atrial recordings from 14 persistent AF patients undergoing cardiac surgery, collected with a high-density grid electrode array (interelectrode distance of 3 mm).20 They demonstrated that endo-epicardial dissociation is highly dynamic and wavefront propagation heterogeneous, suggesting that targeting a single focus of the endo-epicardial dissociation or breakthrough is unlikely to prevent recurrence of AF. This is consistent with the concept of ExTRa Mapping, in which persistent AF encountered in clinical practice is mostly driven by spatially and temporally unstable rotors rather than stationary stable rotors.5 To rapidly predict the atrial excitation during AF, both a computer simulation (in silico) part and special artificial intelligence part were incorporated into the ExTRa Mapping system. The in silico part computed virtual atrial action potentials based on an in silico model of the human persistent AF in combination with the timing of the action potential generation determined by the intra-atrial signals.21 Recent experiments have successfully shown that the phase map sequence of ExTRa Mapping is consistent with high-resolution optical mapping.6Ashihara et al. demonstrated a great catheter ablation outcome using ExTRa Mapping in persistent AF patients for maintaining sinus rhythm.5 This indicated that NPAs detected by ExTRa Mapping should contain the true AF drivers. Therefore, we believed that ExTRa Mapping would provide a more specific ablation target relevant to the cause of AF.
It was previously reported that AF recurrence correlated with the emergence of new AF drivers after catheter ablation, where they occurred in locations distinctly different from those of the original ones.22 To eliminate all of them, electrophysiological mapping, such as ExTRa mapping, should be performed repeatedly, however, it would result in a prolongation of the procedure time. Considering this issue, LGE-MRI is useful for planning the ablation strategy, as it can narrow down the target to be ablated preoperatively.