Cardiac magnetic resonance for assessment of pulsed field ablation-induced ventricular septal lesions: correlation with pathology and functional outcomes in a porcine model

Background ：Cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement (LGE) is widely used for detecting myocardial fibrosis and scar formation. While CMR has been applied to evaluate atrial lesions after pulsed field ablation (PFA), its utility for assessing ventricular septal injury induced by PFA remains unclear. Objective This study aimed to evaluate the feasibility of CMR for detecting and monitoring PFA-induced interventricular septal lesions and to investigate the efficacy and durability of PFA in a porcine ventricular model using the VARIPULSE™ variable-loop circular catheter (VLCC) system. Methods Eight juvenile swine were randomized into acute (n = 4) and chronic (n = 4) cohorts. PFA was performed on the interventricular septum (IVS) under CARTO 3 electroanatomic mapping guidance. Multimodality assessments included electroanatomic mapping, serial CMR (Baseline, Day 0, Day 21, Day 42), transthoracic echocardiography (TTE), and pathological examination. Lesion depth, morphology, and functional parameters were analyzed. Correlation and agreement between CMR and pathology were assessed using linear regression, intraclass correlation coefficient (ICC), and Bland–Altman analysis. Septal motion changes were evaluated by CMR and echocardiography at Day 0, Day 21, and Day 42. Results All targeted sites were successfully ablated. Immediate post-ablation mapping revealed significant reductions in voltage and marked increases in pacing threshold (Pre-PFA vs. Day 0: voltage, 5.13 ± 2.74 mV vs. 0.51 ± 0.25 mV; P < 0.0001; pacing threshold, 1.0 ± 0.00 mA vs. 14.29 ± 7.55 mA; P < 0.0001), with partial recovery at Day 42 but persistent differences versus baseline. Macroscopic and microscopic evaluations confirmed typical PFA lesion features: acute hemorrhage and necrosis with contraction bands transitioning to well-demarcated fibrotic scars. Lesion depth decreased over time (Day 0 vs. Day 21 vs. Day 42: 4.52 ± 1.65 mm vs. 3.68 ± 2.04 mm vs. 3.29 ± 1.64 mm; P < 0.05). TUNEL indicated apoptosis as a primary injury mechanism. CMR-LGE consistently localized lesions as pathology, showing similar lesion depth evolution trend as pathology. Strong correlation and agreement were observed between CMR-LGE and pathology for lesion depth (r = 0.77; ICC = 0.74; mean difference, P = 0.97). Dynamic LGE evolution with significant reductions in mass and volume by Day 21 and stabilization at Day 42. Functional analysis revealed transient impairment of left ventricular ejection fraction (LVEF) and septal strain, with partial recovery by Day 42. Conclusion CMR provides accurate and reliable assessment of PFA-induced ventricular lesions and their temporal evolution, providing robust support for long-term postoperative monitoring and management. Furthermore, PFA applied to interventricular septal ablation creates durable and well-demarcated lesions, supporting its potential application for septum-related ventricular interventions.fig1fig2