Introduction: One treatment option for patients suffering from atrial fibrillation (AF) is to isolate the pulmonary veins, which has a very high success rate in paroxysmal AF patients. However, in patients with persistent AF, the success rate can be as low as 30%. One reason is that the additional arrhythmogenic substrate in the atria is responsible for maintaining the arrhythmia. These areas can be identified by locating low voltage areas <0.5 mV during sinus rhythm (SR), or <0.3-0.5 mV during AF. We recently reported that a high correlation exists between mapping in the two different rhythms. However, this correlation differs between different regions of the atria.  

Purpose: To study the differences between mapping in SR and AF in different atrial regions and identify if regional thresholds can improve the cross-rhythm correlation.

Methods: Twenty-eight persistent AF patients underwent high-density voltage mapping during both SR and AF. The electro-anatomical mapping was performed using the CARTO-3 software and a 20-pole Lasso-Nav catheter (electrode size 1mm, spacing 2-6-2mm). A mean left atrial geometry was derived for the cohort and the patient's voltage values were projected onto this mean anatomical model. The mean voltage across all patients at each mapping site was calculated for both rhythms, then the difference between them was determined. Additionally, the geometry was split into six anatomical regions: left atrial appendage (LAA), anterior, posterior, and lateral wall, roof, and septum. The optimal AF threshold was identified for each region, which correlated to low voltage areas during SR <0.5 mV. 

Results: The highest voltages were found in the left atrial appendage, with the anterior wall presenting the lowest voltages during both rhythms. Across the entire atria, the voltage values were lower, differing between 0-1.2 mV, when mapping during AF than SR. However, the difference between rhythms differed across the atria with the lowest agreement between SR and AF voltages observed at the roof and the posterior wall. The difference in voltage between the two rhythms was highly significant (p<0.001) for each region.

Applying regional thresholds had little effect on the cross-rhythm classification agreement at the anterior wall. However, decreasing the threshold by 0.05 mV improved the accuracy on the posterior wall by 10%. Increasing the threshold at the lateral wall improved the accuracy by 5%.  

Conclusion: A universal threshold for mapping during AF is sufficient for most regions with a limited reduction in the accuracy compared to SR low voltage <0.5 mV. However, the substrate on the posterior and lateral wall targeted for ablation may be more accurately identified using tailored thresholds during AF mapping.