Catheter radiofrequency (RF) ablation is an effective therapy for cardiac arrhythmias such as scar-related ventricular tachycardia (VT). However, recurrence rates after VT ablation remain high, partly due to the challenges of locating the critical arrhythmogenic foci and immediately verifying RF lesions’ efficacy. We specifically sought to investigate the capacity of native T1-weighted MRI to visualize RF lesions immediately after an ablation procedure performed via a clinical electroanatomic mapping (EAM) system.
In this preclinical study, we integrated baseline LGE MR images visualizing scar at a high resolution (approximately 1.5mm isotropic) with conventional X-ray and EAM guidance for RF ablation. A follow-up MRI study immediately post-ablation was performed using native T1 MR contrast to assess RF lesions created within the MR-defined arrhythmia substrate (as well as in scar and healthy myocardium). MRI studies, EAM, and ablation were performed in 8 swine with chronic myocardial infarct. Intra-procedural EAM data was registered with the two MRI studies to compare the locations and extents of MRI-derived RF lesions against EAM ablation tags and against measurements from excised tissue.
Native T1-weighted MRI clearly visualized RF lesions in the MR-defined arrhythmia substrate and scarred regions, as well as in healthy myocardium. Ablation patterns delivered in the EAM system matched those visualized in MRI with high accuracy (sensitivity=88.9%, specificity=94.7%), and were closely matched in co-registered datasets with an average displacement of 5.4±3.8mm (N=152 EAM ablation tags). These findings suggest that native T1-weighted MRI can visualize RF lesions targeted to eliminate the MR-defined arrhythmia substrate and can visualize spatial maps of RF lesions within the LV matching RF delivery by a conventional EAM system, thereby providing image-based procedure feedback. Our robust pipeline could be rapidly translated into the clinical workflow for efficient MR lesion visualization and improved assessment of VT ablation success.