Impact of electrode–tissue proximity on formation of pulsed field ablation lesions: Using multi-electrode impedance measurements

Abstract

Background: For pulsed field ablation (PFA), the effect of electrode–tissue contact or proximity remains unclear. Objective: In this porcine study, the effect of electrode–tissue proximity was studied after 3 weeks of follow-up, using a custom device in which the electrode–tissue distance could be varied for every electrode. Methods: An impedance-based method was used to determine electrode–tissue proximity or contact. During a bench experiment, the relation between contact value per electrode and electrode–tissue distance was studied. In addition, in 10 pigs epicardial ablation using a custom 6-polar linear ablation device was performed using bipolar, biphasic deliveries on randomized locations on the heart. After 3 weeks, macroscopic analysis was used to compare lesion width for left vs right ventricle. Based on histology, the lesion area and depth were related to electrode–tissue contact. Results: Analysis of 96 bench measurements showed a decrease in tissue-proximity index with increasing distance. Lesions on the right ventricle were wider compared to the lesions on the left ventricle, 9.0 ± 1.9 mm vs 6.5 ± 1.0 mm (P < .001), respectively. A total of 162 lesions showed that a higher tissue-proximity index was associated with deeper and larger lesions; lesion depth was 1.3 ± 0.5 mm vs 1.5 ± 0.5 mm (P = .016) and lesion area 6.4 ± 2.7 mm2 vs 8.3 ± 2.9 mm2 (P < .001) for low vs high indices respectively. Conclusion: This study shows that higher electrode–tissue proximity may result in deeper PFA lesions, and is, therefore, an important parameter in improving PFA lesions. Therefore, confirmation of tissue contact using impedance-based measurements may improve PFA ablation efficacy in a clinical setting.