Local Atrial Conduction Velocity During Pacing as Indication of Atrial Fibrillation Substrate Complexity

Background: Pulmonary vein isolation (PVI) as treatment for atrial fibrillation (AF) is not effective in up to 60% of patients with persistent AF; AF drivers outside of the pulmonary veins can contribute to AF recurrences after PVI. In this study we explored the potential use of local conduction velocity (CV) during pacing as a marker of left atrial (LA) substrate complexity.Methods: LA activation times were recorded for 7 AF patients during coronary sinus (CS) pacing before PVI using a Pentaray catheter. Activation times were relative to the CS pacing spike. LA activation locations were triangularized to calculate CV: the local direction and speed of the activation wave front. CV was quantified by the total CV distribution.Results: A mean of 1622 CVs were calculated per patient. Distribution of CVs showed a similar morphology, with median CVs in the range [0.26, 0.36] and interquartile ranges in the range [0.29, 0.39].Conclusion: This study shows that although it is feasible to calculate CVs based on sequential CARTO mapping of the LA during CS pacing, the resulting distribution of CVs using this procedure is not necessarily able to identify substrate complexity because of the large similarity between distributions and the relatively small differences in medians.