Po-03-067 potential negative impact of in situ large lesion formation in porcine and canine animals

A significant amount of information regarding large lesion formation has emerged over the last 5 – 6 years. Extensive studies have been performed with needle electrode, PFA ablation and protons. The consequence of large lesions have not been analyzed in the intact heart in situ. This study aim was to compare how large lesions were created by needle and proton beam ablation in animal models, and to establish adequate energy power. Twenty-two dogs underwent ablation with a needle electrode. The effect of large lesions from proton therapy was also examined in 28 pigs. The lesion size, potential myocardial disruption, or perforation were examined in each of these animal sets. Similarly, findings from PFA ablation were considered. Of these animals, 35 had normal myocardium, while 15 had undergone prior infarction creation. The target location for needle electrode ablation was established by ultrasound, CT and MR, while CT and MR were utilized for establishing the dose response range and targets for proton therapy. These were examined ultimately by an MR study immediately before animal euthanasia, where upon the lesion size was established. In the animals with normal myocardium, the lesions were largely confined to the desired target. Lesions were of substantial size with 1038 ± 887 mm3 from needle electrodes, and 3500 ± 2100 mm3 from protons. In contrast, with myocardial infarction, there was a ven overlap between the lesion created by myocardial infarction and that created by either needle or proton deliveries. The needle electrode and proton delivery large lesions were seen in the table. The large lesions were confined to the area of the infarct in those animals. There was relatively little scatter of demonstrable lesions in the residual myocardium at risk. There were regions around both needle electrode and proton beam deliveries consistent with lower outputs in both cases. In needle electrode deliveries was significant edema farfield around the major lesion, while there was some penumbral proton effect at levels of 10-20 Gy. Both needle, proton, and PFA deliveries create very large lesions in ventricular myocardium. While this could be of substantial risk, the overall lesions are confined to the target dose of needle/PFA and proton targets. This indicates there is relatively little damage to residual myocardium at risk without negative of decreased myocardial contraction. This must be carefully determined, in setting temperature, radiation, and PFA dosing.Tabled 1Table (PO-03-067)Needle normal tissueNeedle infarct tissueProton normal tissueProton infarct tissuePower40 W/50 s50 W/60 s40 W/50 s30 Gy40 Gy40 GyLesion volume (mm3)983±9061093±8681052±5432500±8005900±9003476±1018Width (mm)17.3±5.823.6±14.914.0±3.722.4±3.432.1±7.825.1±3.6Length (mm)14.9±5.914.7±4.217.1±5.413.3±2.114.9±3.613.8±3.4Depth (mm)13.4±2.913.4±3.315.3±2.213.7±2.515.5±3.714.3±2.8Depth at maximum width (mm)7.6±2.18.3±2.37.9±1.79.4±3.19.1±2.49.2±2.0 Open table in a new tab