Introduction: Ablation for atrial fibrillation (AF) carries a significant risk of esophageal injury, including esophageal wall ulceration, peri-esophageal injury or life-threatening atrio-esophageal fistula (AEF). Current methods of esophageal protection are invasive, expensive and their cost-effectiveness is debatable. Standard placement of dispersive patch electrode (DPE) at patient’s back may expose the esophagus to thermal injury from radiofrequency (RF) currents. Repositioning the DPE to the anterior chest could theoretically protect the esophagus from thermal injury, however, such an approach has not yet been investigated. Methods: We retrospectively analyzed three cohorts of consecutive patients undergoing patients RFCA-based pulmonary vein isolation (PVI). The first cohort underwent PVI performed using a multi-electrode PVAC catheter with the DPE placed either anteriorly or posteriorly. The second cohort underwent point-by-point RFCA, including mapping of pulmonary vein ostia and impedance measurements, with DPE placed anteriorly and posteriorly during impedance measurements. The third cohort underwent high-power short-duration (HPSD) PVI with an anterior DPE placement. Impedance values, procedural characteristics, and follow-up outcomes were compared across the cohorts. Results: The first cohort included 62 patients (25 females, age 60 ± 12 years). Forty of them had DPE placed posteriorly and 22 anteriorly. There were no major procedural complications. AF recurrence rates at one-year follow-up did not differ significantly between the anterior and posterior DPE groups (23% vs 43%, log-rank p = 0.074). The second cohort consisted of 12 patients (2 females, age 61 ± 10 years) undergoing point-by-point PVI. Significant impedance differences were observed between posterior and anterior DPE placements for both Erbe DPE (131±14 Ω vs 147±16 Ω, p<0.0001) and Covidien DPE (117±14 Ω vs 125±17 Ω, p=0.018). No complications were reported during a 7±5 months of follow-up. The third cohort included 83 patients (51 males, mean age 62±12 years) undergoing HPSD PVI. All pulmonary veins were successfully isolated. No AEF or esophageal injuries were reported during a mean follow-up of 7±5 months. Conclusions: Anterior position of the DPE during RFCA-based PVI is safe, feasible, non-traumatic and is not associated with any additional cost. Its potential to prevent esophageal complications should be further investigated in prospective studies.

Introduction. Precise electrocardiographic localization of accessory pathways (AP) can be challenging. Seminal AP localization studies were limited by complexity of algorithms and sample size.We aimed to create a non-algorithmic method for AP localization based on color-coded maps of AP distribution generated by a web-based application. Methods. APs were categorized into 19 regions/types based on invasive electrophysiologic mapping. Preexcited QRS complexes were categorized into 6 types based on polarity and notch/slur. For each QRS type in each lead the distribution of APs was visualized on a gradient map. The principle of common set was used to combine the single lead maps to create the distribution map for AP with any combination of QRS types in several leads. For the validation phase, a separate cohort of APs was obtained. Results. A total of 804 patients with overt APs were studied. The application used the exploratory dataset of 552 consecutive APs and the corresponding QRS complexes to generate AP localization maps for any possible combination of QRS types in 12 leads. Optimized approach (on average 3 steps) for evaluation of preexcited ECG was developed. The area of maximum probability of AP localization was pinpointed by providing the QRS type for the subsequent leads. The exploratory dataset was validated with the separate cohort of APs (n = 260); p = 0.23 for difference in AP distribution. Conclusions. In the largest dataset of APs to-date, a novel probabilistic and semi-automatic approach to electrocardiographic localization of APs was highly predictive for anatomic localization.