Cardiac magnetic resonance - aided ventricular tachycardia substrate ablation

Abstract

Abstract Objectives To assess feasibility and reliability of Cardiac magnetic resonance (CMR)-derived pixel signal intensity (PSI) maps obtained by Three Dimensional (3D)- Late Gadolinium Enhancement (LGE) images for detecting potential targets for VT substrate ablation procedures. Background Parametric imaging with color-coded PSI maps obtained from pre-ablation 3D LGE -CMR imaging can be used for identification and characterization of arrhythmic abnormal substrate. Recent publications have shown that PSI maps permit visualization of border zone areas inside the scar. Specifically, corridors of viable tissue within the scar connecting healthy myocardium define VT corridors that may be the electrical equivalent of the abnormal conducting channels on the electroanatomical mapping (EAM). Methods 8 patients with scar-dependent monomorphic VTs who underwent 3D-LGE CMR imaging prior to substrate ablation were included in the study. The studies were performed at 1.5T scanner. We obtained two data sets of 3D whole heart LGE imaging with high resolution. Patients underwent two acquisitions: the conventional respiratory navigated, electrocardiographically-gated 3D fast gradient echo (1.3slice thickness, 256x256 matrix acquisition) and the image-navigated isotropic high resolution 3D GE with Dixon water-fat separation. 3D LGE-CMR images were processed with ADAS-VT software to produce a 3-dimensional model of the heart with 10 layers from the endocardium to epicardium and PSI maps color-coded from the LGE data projected to each of the shells (Figure 1). In the LGE-CMR PSI maps, VT corridors were obtained automatically by the ADAS VT software. Subsequently, data were given to the electrophysiologists and merged with the CARTO3 system EAM data obtained for the ablation (Figure2). CMR information was used to facilitate the identification of target ablation sites in the areas identified by CMR as abnormal substrate and radiofrequency was applied in the presence of both a pathological electrogram (EGM) and a VT corridor as identified by CMR. Results There was a 95% agreement between the abnormal conducting channels as detected by abnormal electrograms in the EAM and the VT corridors identified by 3D LGE CMR imaging. In two occasions, there was one VT corridor that did not correlate with abnormal electrograms and was not ablated. The two 3D LGE sequences used for ADAS-VT corridors analysis showed complete agreement in the number and location of VT corridors. Mean acquisition time for 3D LGE imaging was 11±4minutes for the conventional fast gradient echo sequence, and 5±2minutes for the novel 3D self-image navigated LGE sequence. The image quality of 3D LGE was superior with the Dixon fat-water separation. Overall CMR-aided VT ablation reduced the procedural and fluoroscopy time by 40%. Conclusions CMR-aided VT ablation is feasible, reliable and significantly reduces the procedural time.