Real-time magnetic resonance imaging–guided radiofrequency atrial ablation and visualization of lesion formation at 3 Tesla

Abstract

Background MRI allows visualization of location and extent of RF ablation lesion, myocardial scar formation, and real-time (RT) assessment of lesion formation. In this study, we report a novel 3-Tesla RT-MRI based porcine RF ablation model and visualization of lesion formation in the atrium during RF energy delivery. Objective To develop of a 3-Tesla RT-MRI based catheter ablation and lesion visualization system. Methods RF energy was delivered to six pigs under RT-MRI guidance. A novel MRI compatible mapping and ablation catheter was used. Under RT-MRI this catheter was safely guided and positioned within either the left or right atrium. Unipolar and bi-polar electrograms were recorded. The catheter tip-tissue interface was visualized with a T1-weighted gradient echo sequence. RF energy was then delivered in a power-controlled fashion. Myocardial changes and lesion formation were visualized with a T2-weighted (T2w) HASTE sequence during ablation. Results Real-time visualization of lesion formation was achieved in 30% of the ablations performed. In the other cases, either the lesion was formed outside the imaged region (25%) or lesion was not created (45%) presumably due to poor tissue-catheter tip contact. The presence of lesions was confirmed by late gadolinium enhancement (LGE) MRI and macroscopic tissue examination. Conclusion MRI compatible catheters can be navigated and RF energy safely delivered under 3-Tesla RT-MRI guidance. It is also feasible to record electrograms during RT imaging. Real-time visualization of lesion as it forms during delivery of RF energy is possible and was demonstrated using T2w HASTE imaging.

2012 HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: Recommendations for Patient Selection, Procedural Techniques, Patient Management and Follow-up, Definitions, Endpoints, and Research Trial Design

“…Although these systems are still under development and are not available with routine clinical use at this time, this is an area of considerable interest that could emerge as an important ablation monitoring and guidance strategy in the future. 792,793,794,795 …”

Dynamic T2 Signal Changes on MRI after Radiofrequency Ablation Injury to the Atrial Myocardium

“…While post-ablation T2 signal has been shown to increase and even expand beyond the sites of ablation injury [10,13], the time of onset and resolution of T2 signal following ablation is not well studied. In this paper we describe the temporal course of postablation injury on T2w imaging using data from humans and a porcine model.…”

“…Within 24 hours post-ablation, increased T2 signal is seen in regions with injuries both transient (edema and inflammation) and permanent (tissue necrosis becoming scar) [7,11,12,13]. As a result, postablation T2 signal is not seen as a good predictor of subsequent scar formation [14].While post-ablation T2 signal has been shown to increase and even expand beyond the sites of ablation injury [10,13], the time of onset and resolution of T2 signal following ablation is not well studied. In this paper we describe the temporal course of postablation injury on T2w imaging using data from humans and a porcine model.…”

“…More recently, there has been increasing interest in visualizing the immediate post ablation injury to better understand its effect on LA remodeling and the success of the procedure [8]. Within 24 hours post-ablation, dark regions of no-reflow on LGE MRI have been shown to correlate with regions of myocardium that eventually become scarred [9,10]. Study of the acute ablation injury using T2w sequences also has been described.…”

Cardiac Electrophysiology Under MRI Guidance: an Emerging Technology

“…49 This was followed by a three-dimensional late gadolinium enhancement acquisition at 20 min. However, only 30 % of lesions could be visualised during ablation.…”