Abstract 19251: Identification of Conducting Channels by Delayed Enhanced Cardiac Magnetic Resonance Imaging
Objective: Delayed enhanced cardiac magnetic resonance imaging (DE-CMRI) is able to define a heterogeneous zone of fibrotic tissue and surviving myocytes, known as ‘gray zone’ (GZ). Studies suggest that the GZ is related to ventricular tachycardia (VT) slow conducting channels (CC). There are established algorithms for GZ characterization. We evaluated the correlation of DE-CMRI defined CC and VT electroanatomic maps (EAM).
Methods: Preprocedural DE-CMRI for scar evaluation and electrophysiology study were done in 14 male patients with ischemic (10) and non-ischemic (4) cardiomyopathy and VT. GZ was assessed on contiguous two-dimensional (2D) short axis DE-CMRI slices and reconstructed three-dimensional (3D) models. The reconstructed scar models were integrated in a clinical mapping system and compared to EAM. GZ were defined based on previously described signal intensity (SI) thresholds; full-width half maximum (FWHM), n-standard deviation (NSD) using 2-3SD thresholds and ‘Roes’ (≥ 35% - 50% of peak SI as GZ, and > 50% of peak SI as core).
Results: CMRI and scar detection was possible in all patients including 64% of the patients with ICDs. Software analysis allowed detection and reconstruction of scar core and GZ on all 2D- and 3D-CMRI image series. Scar core and GZ were detected with all 3 algorithms. There was more scar core by NSD (NSD vs. Roes vs FWHM, 27±11g vs. 17±8g vs 17±8g, p < 0.01 ) but more GZ by FWHM (NSD vs. Roes vs. FWHM, 5±2g vs. 8±3g vs 12±7g, p < 0.01 ). CC were detected by CMRI in 50% (NSD), 64% (Roes) and 64% (FWHM) of patients. Compared to 12 CC seen on EAM, there were 17 CC seen by FWHM and Roes and 11 CC by the NSD method. There were 14 successful ablation sites in 12 patients with 2 (14%) located in EAM defined CC compared with 18% (FWHM and Roes) and 9% (NSD) in CMRI defined CC. Above 80% of the ablation sites were located in GZ areas on DE-CMRI for all algorithms (91%, 82% and 91% for NSD, Roes and FWHM).
Conclusion: CMRI defined GZ/channels can be detected by established algorithms and compared with EAM. The FWHM has the highest GZ mass and FWHM/Roes visualize more CC. More than 80% of successful ablation sites are located in direct vicinity of the GZ. This may enable a more refined analysis of the MRI scar substrate with important features for the successful ablation sites.
- © 2012 by American Heart Association, Inc.