Background-Permanent coronary artery damage is a hazardous complication of epicardial radiofrequency ablation.Irreversible electroporation (IRE) is a promising nonthermal ablation modality able to create deep myocardial lesions. We investigated the effects of epicardial IRE on luminal coronary artery diameter and lesion depth. Methods and Results-In 5 pigs (60-75 kg), the pericardium was exposed using surgical subxiphoidal epicardial access. A custom deflectable octopolar 12-mm circular catheter with 2-mm ring electrodes was introduced in the pericardium via a steerable sheath. After coronary angiography (CAG), the proximal, mid, and distal left anterior descending, and circumflex coronary arteries were targeted with a single, cathodal 200 J application. CAG was repeated after IRE and after 3 months follow-up. Using quantitative CAG, the minimal luminal diameter at the lesion site was compared with the average of the diameters just proximal and distal to that lesion. Study ProtocolThe study was performed in 6 pigs (weight 60-75 kg). Amiodarone therapy was started 1 week before the index procedure (400 mg once daily) to prevent procedure-related arrhythmias. Carbasalate calcium (80 mg once daily) and clopidogrel (75 mg once daily) therapy was started 3 days before the index procedure and continued until euthanasia. The animals were sedated, intubated, and anesthetized according to standard procedures. Using a surgical subxiphoidal pericardial approach, a custom deflectable octopolar 12-mm circular catheter with 2-mm ring electrodes was introduced in the pericardial space via a 40-cm 8.5F deflectable sheath (Agilis EPI Steerable Introducer; St Jude Medical, St Paul, MN; Figure 1). After left anterior descending artery (LAD) and circumflex coronary artery (RCx) angiography, the mid and distal LAD and RCx were targeted with electroporation catheter ablation ( Figure 2). A single, cathodal 200 J application was delivered. This was repeated at 2 or 3 different locations over the LAD and RCx while avoiding overlap. The energy was generated by a monophasic external defibrillator (Lifepak 9; Physio-Control, Inc, Redmond, WA). A large skin patch (7506; Valleylab Inc, Boulder, CO) on the lower back served as indifferent electrode. A cathodal polarity was chosen because that has the highest threshold for arcing in a blood environment. 13 Coronary angiography (CAG) was repeated after the last application.After 3-month survival, CAG of the LAD and RCx was repeated, the thorax was opened by sternotomy, and the animal was euthanized by exsanguination. After the heart was removed, the pericardium was peeled off and the areas with ablation lesions were excised and fixated in formalin. Measurement of Coronary DiametersLuminal diameters of the coronary artery, proximal and distal to the application site, and the minimal diameter at the application site were measured using quantitative CAG. The latter value was then compared with the average value of the diameters proximal and distal to the application site. Histological Evaluation...

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