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Spatial Correlation of Left Atrial Low Voltage Substrate in Sinus Rhythm versus Atrial Fibrillation: Identifying the Pathological Substrate Irrespective of the Rhythm

Background: Low voltage substrate (LVS) identified during electroanatomical mapping is a potential target for atrial fibrillation (AF) ablation. However, it is not clear how the location and extent of LVS correlate between mapping in sinus rhythm (SR) and AF. Objectives: (1) Identify voltage dissimilarities between mapping in SR and AF. (2) Identification of regional voltage thresholds that improve cross-rhythm substrate detection. (3) Comparison of LVS between SR and native vs. induced AF. Methods: Forty-one ablation-naive persistent AF patients underwent high-density voltage mapping in SR and AF. Each patients voltage information was mapped to a joint geometry for analysis. Global and regional voltage thresholds in AF were identified which best match LVS < 0.5mV and < 1.0mV in SR. Additionally, the correlation between SR-LVS with induced vs. native AF LVS was assessed. Results: Substantial voltage differences (median: 0.52, IQR: 0.33-0.69, max: 1.19 mV) with predominance of the posterior/inferior LA wall exist between the rhythms. An AF threshold of 0.34mV for the entire atrium provides an accuracy, sensitivity and specificity of 69%, 67% and 69% to identify SR-LVS < 0.5mV, respectively. Lower thresholds for the posterior wall (0.27 mV) and inferior wall (0.3 mV) result in higher spatial concordance to SR-LVS (4% and 7% increase). Concordance with SR-LVS was higher for induced AF compared to native AF (AUC: 0.80 vs. 0.73). AF-LVS < 0.5mV corresponds to SR-LVS < 0.97mV using high-definition mapping (AUC: 0.73). Conclusion: The proposed voltage thresholds during AF maximise the consistency of LVS identification as determined during SR. Regional thresholds can further improve concordance.