Biophysics and Electrophysiology of Pulsed Field Ablation in Normal and Infarcted Porcine Cardiac Ventricular Tissue

Pulsed Field Ablation (PFA) is a new ablation method being rapidly adopted for treatment of atrial fibrillation, which shows advantages in safety and efficiency over radiofrequency and cryo-ablation. In this study, we used an in vivo swine model (10 healthy and 5 with chronic myocardial infarct) for ventricular PFA, collecting intracardiac electrograms, electro-anatomical maps, native T1-weighted and late gadolinium enhancement MRI, gross pathology, and histology. We used 1000-1500 V pulses, with 1-16 pulse trains to vary PFA dose. Lesions were assessed at 24 hours, 7 days, and 6 weeks in healthy and at 48 hours in infarcted ventricles. Comparisons of lesion sizes using a numerical model enabled us to determine lethal electric field thresholds for cardiac tissue and its dependence on the number of pulse trains. Similar thresholds were found in normal and infarcted hearts. Numerical modeling and temperature-sensitive MRI confirmed the nonthermal nature of PFA, with less than 2% of a lesion’s volume at the highest dose used being attributed to thermal damage. Longitudinal cardiac MRI and histology provide a comprehensive description of lesion maturation. Lesions shrink between 24 h and 7 days post-ablation and then remain stable out to 6 weeks post-ablation. Periprocedural electrograms analysis yields good correlation with lesion durability and size.

脉冲场消融（Pulsed Field Ablation，PFA）是一种正被快速推广应用于心房颤动治疗的新型消融术式，相较于射频消融与冷冻消融，其在安全性与有效性上更具优势。本研究构建体内猪模型（含10只健康猪与5只慢性心肌梗死模型猪）开展心室脉冲场消融实验，同步采集心内心电图（intracardiac electrograms）、电解剖标测图（electro-anatomical maps）、非对比增强T1加权磁共振成像（native T1-weighted MRI）、延迟钆增强磁共振成像（late gadolinium enhancement MRI）、大体病理学结果及组织学样本。本研究采用1000~1500 V的脉冲电压，通过1~16组脉冲序列调节脉冲场消融的剂量参数。针对健康猪模型，分别于消融后24小时、7天及6周对消融损伤灶进行评估；针对梗死心室模型，则于消融后48小时开展评估。通过数值模型对比消融损伤灶尺寸，本研究明确了心肌组织的致死电场阈值，及其与脉冲序列数量的依赖关系；健康心肌与梗死心肌的致死电场阈值无显著差异。数值模拟与温度敏感性磁共振成像验证了脉冲场消融的非热效应特性：在最高剂量组中，仅不足2%的消融损伤灶体积由热损伤导致。纵向心脏磁共振成像与组织学分析全面揭示了消融损伤灶的成熟过程：消融后24小时至7天期间，损伤灶体积逐渐缩小，随后至消融后6周均保持稳定。围手术期心内电信号分析结果与消融损伤灶的持久性及尺寸具有良好的相关性。