Abstract
Real-time magnetic resonance imaging (MRI)-guided electrophysiology (MR-EP) offers a number of potential advantages over conventional electroanatomic mapping (EAM) systems, including improved assessment of arrhythmia structural substrate using late gadolinium enhancement (LGE) scar imaging, navigation of catheters using dedicated tracking techniques and monitoring of ablation lesion formation with soft tissue visualisation. Registration errors due to changes in the volume, orientation, rhythm, cardiac or respiratory motion between the time of pre-procedural imaging and EAM, as is typical with image integration approaches, are also minimised during real-time MR-EP. Although the majority of real-time MR-EP studies published to date have focused on the atria, where significant challenges remain for accurate substrate evaluation, the full potential of substrate and lesion assessment afforded by such systems is likely to be realised in the context of ventricular tachycardia (VT) ablation.This thesis explores the use of a real-time MR-EP system for the assessment of structural and electrical substrate in the ventricle. Furthermore, the accuracy of the system is evaluated in the delivery of radiofrequency (RF) ablation lesions and online monitoring of lesions using dedicated imaging techniques. Chapters 1 and 2 review the literature on the electrophysiology of ventricular tachycardia and magnetic resonance imaging. Chapter 3 describes in detail the methods common to the data chapters including the animal model, imaging approaches and MR-EP workflow. In Chapter 4, a method of contrast delivery using a slow infusion of gadolinium (contrast steady-state) is used to enable LGE scar imaging over a prolonged period, thereby enhancing the spatial resolution of 3D sequences and improve the characterisation of structural substrate. A porcine ischaemia-reperfusion model is used to compare post-contrast 3D sequences under consistent contrast conditions whilst the technique is also applied in a feasibility cohort of ischaemic cardiomyopathy patients.
In Chapter 5, the contrast steady-state technique is then used to acquire high resolution 3D scar imaging in the porcine model with the real-time MR-EP system. The relationship between structural and electrical substrate with the system is assessed. In Chapter 6, the accuracy of the MR-EP system to deliver ablation lesions in target regions is evaluated and lesion sizes measured using temperature mapping (MR-thermometry and dosimetry) and a non-contrast sequence (gradient-echo with a long inversion time) are compared to gross pathological examination. Chapter 7 summarises the results and describes further studies to advance the field.
| Date of Award | 1 Jul 2020 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Reza Razavi (Supervisor) & Mark O'Neill (Supervisor) |