Three-Dimensional Architecture of Scar and Conducting Channels Based on High Resolution ce-CMR

Abstract

Background-Conducting channels are the target for ventricular tachycardia (VT) ablation. Conducting channels could be identified with contrast enhanced-cardiac magnetic resonance (ce-CMR) as border zone (BZ) corridors. A 3-dimensional (3D) reconstruction of the ce-CMR could allow visualization of the 3D structure of these BZ channels. Methods and Results-We included 21 patients with healed myocardial infarction and VT. A 3D high-resolution 3T ce-CMR was performed before CARTO-guided VT ablation. The left ventricular wall was segmented and characterized using a pixel signal intensity algorithm at 5 layers (endocardium, 25%, 50%, 75%, epicardium). A 3D color-coded shell map was obtained for each layer to depict the scar core and BZ distribution. The presence/characteristics of BZ channels were registered for each layer. Scar area decreased progressively from endocardium to epicardium (scar area/left ventricular area: 34.0±17.4% at endocardium, 24.1±14.7% at 25%, 16.3±12.1% at 50%, 13.1±10.4 at 75%, 12.1±9.3% at epicardium; P<0.01). Forty-five BZ channels (2.1±1.0 per patient, 23.7±12.0 mm length, mean minimum width 2.5±1.5 mm) were identified, 85% between the endocardium and 50% shell and 76% present in ≥1 layer. The ce-CMR-defined BZ channels identified 74% of the critical isthmus of clinical VTs and 50% of all the conducting channels identified in electroanatomic maps. Conclusions-Scar area in patients with healed myocardial infarction decreases from the endocardium to the epicardium.BZ channels, more commonly seen in the endocardium, display a 3D structure within the myocardial wall that can be depicted with ce-CMR. The use of ce-CMR-derived maps to guide VT ablation warrants further investigation.

Electrophysiology Model for a Human Heart with Ischemic Scar and Realistic Purkinje Network

“…1). Previous studies [5,13] have shown a moderate correlation between the scar regions obtained from EAM by bipolar voltage thresholds (<0.5 mV for the scar and 0.5-1.5 mV for the borderzone) and the DE-MRI-derived endocardial scar regions, so that we took treated the DE-MRIderived scar regions as having been previously validated. Simulations were run for both the cases where the scar region was assumed to be nonexcitable tissue (not shown) and excitable tissue with the parameters identified by the nonlinear fitting procedure.…”

“…The segmentation thresholds have been previously optimized using EAM data in [1,5]. These thresholds have been used to successfully identify borderzone conducting channels during catheter ablation.…”

“…After projecting the intensity values to a surface mesh segmentation of the LV, 4,000 radial basis function interpolation sites are randomly seeded on the endoand epicardial surfaces respectively. The intensity values are interpolated using inverse multi-quadric shape functions and used to choose the appropriate membrane model parameters using the same criterion as in [5] that intensity above >60% of maximum is considered scar, while <40% of the maximum is considered healthy tissue -everything in between is considered borderzone.…”

“…1. Scar and its borderzone identified from DE-MRI according to the criteria in [5]. Color scheme indicates red for deep scar, blue for borderzone, and white for healthy myocardium.…”

Cardiac Electrophysiology Under MRI Guidance: an Emerging Technology

“…CMR-derived targets may typically be 2-4 mm wide for VT ablation 10,18 and even smaller for atrial ablation. 14,19 Small errors in registration mean that either a broad region must be ablated or critical targets left untouched, with consequent impact on safety, time and efficacy.…”