MR Thermometry for radiofrequency ablation in atria and ventricles, a key point for efficacy and safety – CARTLOVE

Catheter ablation is the cornerstone of curative treatment for arrhythmia however the success rate of this procedure for complex arrhythmia like ventricular tachycardia and atrial fibrillation, requiring a complete electrical isolation, is currently limited by the lack of visualization of the lesion formation during the procedure. The CARTLOVE project aims to overcome the limit of radiofrequency ablation for the treatment of cardiac arrhythmias, by demonstrating that immediate visualization in response to catheter ablation is possible through MR-thermometry.

The adoption of MR-guided electrophysiology includes the possibility of real-time adjustment of the optimal radiofrequency energy that must be delivered to the tissue to ensure complete destruction of the arrhythmogenic substrate and could considerably reduce the occurrence of redo-procedures. MR-thermometry (at 1°C uncertainty) for ablation monitoring in the atrium requires improvement in image spatial resolution as the atrial wall ranges between 2 to 5 mm. To achieve this goal of 1x1x1mm3 voxel size or better while preserving fast acquisition, two new MR acquisition and reconstruction methods will be developed on a 1.5 T clinical scanner: a 2D simultaneous multi-slice echo planar imaging acquisition and a 2D radial golden-angle sequence.Simultaneous multi-slice methods are increasingly used for a variety of MRI sequence as it allows a faster acquisition time while preserving the signal-to-noise ratio. Simultaneous multi-slice echo planar imaging acquisition promises to be a method of choice for therapy guidance using MR-thermometry for which both high temporal resolution and sufficient volume coverage are mandatory to characterize the lesion formation during the treatment. The second method relies on a non-cartesian sampling of the k-space that offers intrinsic robustness to motion that must be addressed for cardiac MRI. This method provides full flexibility in slice positioning, orientation and spatial resolution and may be an interesting alternative to provide high resolution, motion-robust thermometry in the atrium.

Both methods will be validated on phantoms (in static condition and during mechanical periodic translation to reproduce respiratory motion using an available rocker system), then on isolated perfused hearts from large animals (no respiratory motion but with cardiac contraction, using a MR-compatible setup previously developed at the lab), then in vivo on large animal models during catheter ablation and finally transferred to patients to evaluate the method in presence of arrhythmic episodes (without RF ablation). A partnership with medical equipment companies specializing in the development of MR-compatible catheters will supplement the project.

The expected results of CARTLOVE are the development and evaluation of two new sequences for cardiac temperature monitoring during radiofrequency ablation with high spatial and temporal resolutions, which is of major interest for MR-guided electrophysiology in patients. Feasibility of such a procedure and evaluation of the accumulated thermal dose as a predictor of transmural ablations in large animal models will be conducted as well as assessment of temperature precision in patients suffering from arrhythmia for future clinical deployment.

CARTLOVE has the ambition of improving the safety and efficacy of the therapy by providing an objective therapeutic end-point based on quantitative, rapid and spatially resolved MR-thermometry. From societal point of view, it is expected to reduce overall costs and the number of hospitalization, together with a lower mortality rate in patients with persistent atrial fibrillation or ventricular tachycardia. MRI is a radiation-free technology that will also benefit both patients (in particular pediatric) and operators (absence of accumulated exposure dose to X-ray) in MR-guided electrophysiology procedures.