The Use Cardiac Magnetic Resonance Imaging Techniques in the Management of Atrial Arrhythmias

Abstract

Introduction: The use of cardiac magnetic resonance (CMR) imaging in the performance of cardiac electrophysiological procedures has grown rapidly over the past decade. This thesis focuses on three main strands regarding the integration of CMR techniques within the management of atrial arrhythmias: prior to ablation, during ablation, and after ablation. Methods: Prior to catheter ablation for atrial fibrillation, 89 subjects underwent detailed CMR analysis of the AF substrate, with extended follow-up. In a first-in-man clinical trial of MR-guidance during ablation, 10 subjects underwent treatment for atrial flutter using an ablation catheter with active MR-tracking. Post AF ablation, 40 subjects were enrolled in a cross-over study, with two closely-coupled scan sessions (3 months post-ablation, 48 hour separation, total 6 LGE acquisitions per subject): scar imaging optimisation, reproducibility and thresholding were assessed. Finally, the predictive value of the VisiTag (CARTO3) objective ablation module was evaluated against optimal CMR-assessed scar. Results: Prior to ablation, on multi-variate Cox regression analysis only LA fibrosis was independently associated with outcome. During ablation, MR-guided therapy was performed in 9 (90%) of subjects, with two late arrhythmia recurrences. Post-ablation, it was demonstrated that optimal imaging was performed late (>30min) post-gadolinium injection. Reproducibility of scar imaging was good, and best thresholded using a blood-pool z-score method. VisiTag thresholds should be set relatively low (10g, 15seconds) to avoid a high ablation burden. Conclusions: CMR techniques have an important role to play in the guidance of ablation therapies for atrial arrhythmias. The implementation of these techniques, though, must be performed with a thorough understanding of the capabilities and limitations of CMR. Image acquisition, image processing, engineering constraints and subjective interpretation may lead to false findings, both positive and negative. In this cross-specialty field, cautious and informed utilisation of CMR may in time improve clinical outcomes, but further work is required to establish and confirm the precise role and benefits of the techniques.

Date of Award	2017
Original language	English
Awarding Institution	King's College London
Supervisor	Reza Razavi (Supervisor)