Advanced Real-time MR-Guided Radiofrequency Ablation of Cardiac Arrhythmias

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Cardiac arrhythmias affect 2 million people a year in the UK. Radio-frequency (RF) ablation (RFA) procedures are clinically available to treat the majority of cardiac arrhythmias. Overall, ~20,000 RFA of cardiac arrhythmias are being performed every year in the UK. RFA uses catheter-based localized delivery of radio-frequency energy resulting in localized tissue heating. Sufficient temperature increase (~30-50C for ~30-60sec) is necessary to create permanent tissue destruction (necrosis). The aim of RFA procedures is to create permanent tissue destruction of critical heart tissues causing arrhythmias. This is often achieved by creating lines of permanent ablation lesions to electrically block/isolate these critical sites. Since each ablation point has a maximum size of ~6-8mm, multiple ablations are commonly performed to create ablation lines. Currently, 30-50% of RFA procedures fail due to the presence of gaps in ablation lines and the incorrect location/extent of the permanent RFA lesions. Furthermore, RFA procedures may have severe complications including cardiac perforation which can arise from steam explosion occurring when tissue temperature exceeds 100C. Finally, potential catheter drift during RFA should be prevented to avoid ablation of undesired tissues. Current real time RFA guidance systems (X-ray, electro-anatomical mapping) are unable to monitor tissue temperature and extent of permanent RFA lesions. Indirect parameters such as RF power/duration, catheter tip temperature, catheter contact force/impedance are monitored during RFA but have low predictive values of tissue temperature and permanent RFA lesion extent. Notably, the discrepancy between the catheter-tip temperature and tissue temperature can be >30C. Therefore, real time accurate monitoring of tissue temperature and prediction of permanent RFA lesion extent is very likely to improve the outcome and safety of the procedure.Magnetic resonance (MR)-thermometry is a non-invasive MRI technique which enables real time pixel-wise assessment of temperature, deep in tissue. Permanent tissue destruction can be predicted using the concept of thermal dose (thereafter referred to as MR-dosimetry) which is based on a model of temperature elevation and time of exposure. However, current cardiac MR-thermometry/dosimetry methods that are not ideal for clinical translation (long acquisition window, low spatial resolution, sensitivity to physiological motion, and high noise level in temperature maps) and a clinically feasible method remains still to be demonstrated, as does its accuracy for prevention of ablation gaps and prediction of chronic permanent RFA lesion extent. This research proposal aims to develop a novel clinically feasible real-time cardiac MR-thermometry/dosimetry framework which addresses the current unmet need, to evaluate its performance in a pre-clinical study, and to demonstrate its feasibility in a first-in-man clinical study.