Evaluation of the thermal effects and footprint of pulse field ablation
J Gill, C Saija, V Sagar, P Shaw, L Leung, K Rhode, M M GallagherAbstract
Background
Pulse field ablation (PFA) uses ultrashort electrical impulses to cause electrolytic degeneration of cellular membranes and reportedly has a minimal temperature footprint [1]. It contrasts to thermal methods of ablation including radiofrequency ablation and cryoablation which cause thermal destruction of tissue.
Purpose
Ex-vivo evaluation of the thermal effects and footprint of PFA using a validated novel temperature sensitive myocardial hydrogel phantom
Methods
A validated thermochromic myocardial hydrogel phantom was used to evaluate the thermal effects of PFA delivery [2]. The phantom hydrogel tissue changes colour when a specific temperature is reached and remains that colour after cooling, allowing analysis of the lesion footprint. Two phantoms models for a 50ºC and 60ºC footprint were used. A non-irrigated over-the-wire circular PFA catheter was used to create lesions on the phantom model in a 36ºC water bath of impedance-controlled saline. Lesions were delivered using the manufacturers generator and waveform. Protocols examining single, overlapping, and directly stacked lesions were performed. The phantom hydrogel lesions were analysed by section through the lesions and measured by 2 independent observers using maximum depth, length and width using a vernier caliper and digital image analysis.
Results
The mean depth of single applications on the 50ºC hydrogel was 1.25mm (SD +- 0.07mm), and 1.1mm (SD+-0.1mm) on the 60ºC hydrogel. The mean length of lesions at the surface was 5.8mm on the 50ºC hydrogel (SD +- 1.1mm) and 5.5mm on the 60ºC hydrogel (SD +- 0.8mm) (Figures 1,2). Stacked applications created thermal effects up to 2.8mm depth measured on the 50ºC hydrogel and a contiguous surface thermal footprint spanning between catheter electrodes.
Conclusion
This data identifies and quantifies a clinically significant thermal footprint of PFA in a commercially available system. Myocardial tissue effects can be seen at 50ºC and therefore clinically relevant thermal tissue damage may occur during PFA application. The tissue-selective benefits of PFA ablation within the thermal footprint may be reduced and could cause damage to non-myocardial structures. In thinner atrial tissue, stacked PFA lesions could have a transmural thermal effect, and vigilance for complications previously thought to be specific to thermal ablation modalities is necessary. Caution should be exercised when describing PFA as a "non-thermal" ablation modality.Thermal footptints on phantom hydrogel