Koya, Taro

Background: Pulsed field ablation (PFA) is a promising modality for treatment of cardiac arrhythmias. PFA increases cell permeability, thereby promoting cell apoptosis. Although greater PFA energy may produce larger lesions, it also carries risks of side effects such as arcing, hemolysis, and microbubbles. Chemical ablation using ethanol (EtOH), such as with injection of the Vein of Marshall, has been used to treat atrial myocardium for refractory atrial arrhythmias. Hypothesis: We hypothesize that PFA in the atria can increase EtOH uptake through PFA-generated pores, thereby augmenting ablation efficacy by utilizing the cell permeability effects of PFA. Aim: The aim of this study is to investigate the effects of local EtOH infusion after PFA on lesion size in porcine atria. Methods: The atria of five porcine subjects were ablated in vivo with low PFA power settings (250V, at 20μs for 50 pulses separated by 200 ms) using a focal bipolar irrigated ablation catheter and BTX 830 electroporation generator (Harvard Apparatus). After PFA, 2 ml of 90 % EtOH vs. saline (control) was infused through the catheter tip to the site of ablation. We compared electrogram voltage amplitude reduction and ablation lesion parameters before and after PFA. Results: A total of 14 control lesions and 14 EtOH lesions were analyzed. There was significant difference in voltage reduction between two groups ( Figure 1A-B ). On gross pathology, there were significant differences in ablation lesion maximum surface diameter, lesion depth, and volume between the 2 lesion sets ( Figure 1C ). Conclusion: Concurrent EtOH infusion after PFA enhanced acute efficacy of electroporation in porcine atria. Adjuvant therapy has the potential to improve efficacy without requiring higher energy parameters, thereby reducing PFA risks. Further studies to assess chronic efficacy are warranted.

AbstractIntroductionPulsed field ablation (PFA) has emerged as an innovative therapy for cardiac arrhythmias. Drawing parallels with PFA's application in solid tumors, calcium chloride (CaCl2) as an adjuvant therapy, known as calcium electroporation, may amplify PFA's apoptotic effects. We propose that PFA in the atrium could enhance calcium uptake through PFA‐created pores, thereby increasing ablation efficacy even at reduced power levels by exploiting PFA's permeabilization effects.MethodsWe conducted in vivo ablations on the atria of seven pigs using low PFA power (250 V, 20 μs for 50 pulses at 200 ms intervals). Post‐PFA, we randomly administered an infusion of either 200 mg/2 ml CaCl2 (calcium group) or saline (control) directly to the ablation site via the catheter tip. We evaluated reduction in electrogram voltage amplitude, electrocardiography (ECG) parameters, ablation lesion parameters, and histology after PFA.ResultsNineteen lesions from control and calcium groups were examined. Control lesions showed no voltage decrease post‐PFA, whereas calcium‐treated lesions exhibited a significant voltage reduction. Gross pathology indicated marked differences in maximum lesion surface diameter, depth, and volume between the lesion groups. Histologically, calcium group lesions were characterized by a more severe acute PFA response with contraction band necrosis, myocytolysis and nuclear pyknosis in adjacent myocardium, in addition to microhemorrhages.ConclusionInfusing calcium chloride locally after PFA markedly improves the immediate efficacy of electroporation in porcine atria. This study suggests that calcium electroporation could bolster PFA outcomes without higher energy levels, potentially diminishing associated risks. These preliminary findings warrant further research into the long‐term efficacy and potential clinical application of calcium electroporation in PFA.