Evaluation of Ablation Lesions Using Cardiovascular Magnetic Resonance Imaging

Catheter ablation has become a cornerstone in the treatment of atrial fibrillation (AF). Typically, radiofrequency ablation (RFA) and cryoballoon ablation are used to perform pulmonary vein isolation (PVI). This treatment is effective in the majority of patients, but nevertheless 35% of patients have arrhythmia recurrence at 1-year follow up. These recurrence rates have been attributed to multiple factors, including ineffective ablation lesions, presence of non-pulmonary vein arrhythmia triggers, and disease progression.

Ineffective ablation lesions can cause arrhythmia recurrence through electrical reconnection. Electrical reconnection can occur when gaps are present in the ablation line due to non-durable, non-transmural or non-contiguous ablation lesions. Conventionally, ablation lesion assessment is performed using a redo electrophysiology study at three months post-ablation. During a redo electrophysiology study, a catheter is used to measure the local electrical signals to enable identification of sites with electrical reconnection. This method is effective but poses the patient to the procedural risks of these invasive measurements. Cardiovascular magnetic resonance (CMR) imaging may provide an alternative method for the evaluation of ablation lesions. Modern acquisition and post-processing techniques are under development and being used to image the atrial wall. These techniques may effectively visualize the fibrous tissue of ablation lesions, which enables a non-invasive method to characterize the lesions of catheter ablation.

To reduce arrhythmia recurrence caused by electrical reconnection, several novel ablation techniques have been developed in the last years. These novel ablation techniques can potentially reduce arrhythmia recurrence by enabling the creation of durable, transmural and contiguous ablation lesions. Novel ablation modalities include ultra-low temperature cryoablation (ULTC) and pulsed field ablation (PFA) that use near-critical nitrogen and pulsed electrical fields to create ablation lesions. The initial clinical outcomes of both ablation modalities are favorable, but little data are available on the ablation lesion characteristics. Additionally, novel techniques were developed to improve the procedural outcomes of RFA. High power, short duration (HPSD) RF energy applications cause more resistive and less conductive tissue heating compared to convention RFA, which results in more durable ablation lesions and less arrhythmia recurrence while safety outcomes are similar.

This study aims to use CMR to evaluate the ablation lesion characteristics of HPSD RFA, ULTC and PFA. This novel information can be used to quantitatively compare different ablation modalities. Furthermore, this study could contribute to our knowledge on ablation lesion formation, which may be used to further develop our ablation strategies.