Po-04-094 relevance of microbubble formation with pulsed field ablation showing irreversible electroporation in a canine model

With ablation using a saline flow catheter tips, occasionally microbubbles will be seen, either from excessive heating or steam pops. The occurrence and implications of microbubble formation with PFA/IRE ablation has not been determined. This study aim was to clarify the means of microbubble during PFA/IRE ablation. Therefore, a total of 4 dogs underwent evaluation with the delivery of 34 ablated lesions in the right and left atrium. During PFA/IRE ablation, we monitored by the ICE imaging whether microbubble formation occurred. With these, microbubbles were seen in 82% of deliveries. The microbubbles were class I in 25 %, class II in 25 %, and class III in 50 %. There appeared to be no untoward effect of class I microbubbles. However, with the others, a suggested biophysical property was seen. In those with catheter positioning directly perpendicular to the endocardial surface, microbubbles were less common. On the other hand, with more parallel tip positioning, or with lowere contact force, microbubbles could reach the class II or III level. These were different than past studies showing simple heat related microbubbles. With PFA the heat is not present. Nevertheless, the process of electrophoresis appeared to create the microbubbles to a greater extent than the irrigation catheter’s flow. The concern with this is a decrease in the effectiveness of delivery as judged by high-density mapping. With this study, no actual perforations were seen, but there was an energy loss with the electrophoretic effects. Actually, in gross pathology, the lesion length and width ranged from 16.5 to 24.1 mm and from 11.9 to 21.8 mm in the RA. Class II or III microbubbles are readily seen in PFA/IRE ablation. These appear to be different from that seen with irrigation-tip catheters. The marked occurrence of microbubbles suggests an electrophoretic process, which like incomplete contact could result in a substantial loss of energy rendering ablation lesions less effective. Even with enough contact PFA/IRE, the effect could be substantial. While few complications are seen with PFA/IRE ablation, the marked electrophoretic effect producing microbubbles, also seen with high output pacing could result in a diminution of the actual lesion formation as judged by histology.