Pulmonary vein isolation plus ablation of additional arrhythmic substrate is used to treat persistent atrial fibrillation (AF) patients. Atrial arrhythmogenic substrate contains increased myocardial fibrosis and displays low bipolar voltage $<$ 0.5\,mV during SR or $<$ 0.3-0.5\,mV during AF. However, discrepancies were reported in the extent and location of low voltage areas (LVA) between SR and AF maps. This paper studies these differences and identifies if regional thresholds can improve the correlation.
Twenty-eight patients with AF underwent high-density voltage mapping during both SR and AF. Each patient's voltage information was projected onto a mean geometry to analyse the spatial accordance of LVA identified during AF at various thresholds with those during SR at 0.5\,mV threshold. The model was split into six regions to identify which regions have the lowest agreement between SR and AF and if regional thresholds could improve this.
Areas of high and low voltage were similar in both mapping modalities. However, differences of $>$ 0.7\,mV occurred on the lateral and posterior wall. When using one threshold for the entire atria, agreement at the posterior wall was $<$ 70\%. This improved by 10\% when using a regional AF threshold. Therefore, substrate targeted for ablation during AF mapping can be more accurately identified on the posterior wall using a lower threshold.