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.