Characteristics and time course of acute and chronic myocardial lesion formation after electroporation ablation in the porcine model

Introduction: Electroporation ablation creates deep and wide myocardial lesions. No data are available on time course and characteristics of acute lesion formation. Methods: For the acute phase of myocardial lesion development, seven pigs were investigated. Single 200 J applications were delivered at four different epicardial right ventricular sites using a linear suction device, yielding a total of 28 lesions. Timing of applications was designed to yield lesions at seven time points: 0, 10, 20, 30, 40, 50, and 60 min, with four lesions per time point. After killing, lesion characteristics were histologically investigated. For the chronic phase of myocardial lesion development, tissue samples were used from previously conducted studies where tissue was obtained at 3 weeks and 3 months after electroporation ablation. Results: Acute myocardial lesions induce a necrosis pattern with contraction band necrosis and interstitial edema, immediately present after electroporation ablation. No further histological changes such as hemorrhage or influx of inflammatory cells occurred in the first hour. After 3 weeks, the lesions consisted of sharply demarcated loose connective tissue that further developed to more fibrotic scar tissue after 3 months without additional changes. Within the scar tissue, arteries and nerves were unaffected. Conclusion: Electroporation ablation immediately induces contraction band necrosis and edema without additional tissue changes in the first hour. After 3 weeks, a sharply demarked scar has been developed that remains stable during follow-up of 3 months. This is highly relevant for clinical application of electroporation ablation in terms of the electrophysiological endpoint and waiting period after ablation.