Ventricular tachycardia (VT) is a leading cause of sudden cardiac death, especially in post-infarction patients. Conventional X-ray guided RF ablation therapy often fails to completely eliminate the VT substrate located deep in the myocardial wall and to accurately assess the therapy outcome, being limited to surfacic voltages maps constructed from intracardiac electrical signals. Magnetic Resonance Imaging (MRI) of the RF ablation-induced changes in cardiac tissue could provide additional crucial information to improve the clinical success of ablation.
In this preclinical study, we proposed a novel method to comprehensively characterize subtle MR features of cardiac RF ablation lesions. We used a real-time MRI-guided electrophysiology (EP) mapping and ablation system to create and visualize RF lesions within the ventricular wall of healthy swine, then measure associated catheter-based electrical signals. Further, we related key features of native-contrast MR-defined lesion components: elevated T2 representing transient edema and hyperintensity in T1-weighted images representing the permanent RF lesion core. These regions were related to the amplitude of intracardiac bipolar electrograms recorded from the precise location of the catheter, co-registered with MR images. Notably, we observed reduced bipolar voltages at the site of the native T1-derived permanent RF lesion core and surrounding T2-derived edematous tissue. While the 3D extent of permanent lesion core and transient edema were clearly delineated in MR images and histologically validated, these injury components were not differentiable using surfacic bipolar voltage alone. The results of this translational study are significant in the context of MR image-guided ablation procedures, whose clinical application is now feasible.