Feasibility of image-based simulation to estimate ablation target in human ventricular arrhythmia

Abstract

Background: Previous studies suggest that magnetic resonance imaging with late gadolinium enhancement (LGE) may identify slowly conducting tissues in scar-related ventricular tachycardia (VT).

Objective: To test the feasibility of image-based simulation based on LGE to estimate ablation targets in VT.

Methods: We conducted a retrospective study in 13 patients who had preablation magnetic resonance imaging for scar-related VT ablation. We used image-based simulation to induce VT and estimate target regions according to the simulated VT circuit. The estimated target regions were coregistered with the LGE scar map and the ablation sites from the electroanatomical map in the standard ablation approach.

Results: In image-based simulation, VT was inducible in 12 (92.3%) patients. All VTs showed macroreentrant propagation patterns, and the narrowest width of estimated target region that an ablation line should span to prevent VT recurrence was 5.0 ± 3.4 mm. Of 11 patients who underwent ablation, the results of image-based simulation and the standard approach were consistent in 9 (82%) patients, where ablation within the estimated target region was associated with acute success (n = 8) and ablation outside the estimated target region was associated with failure (n = 1). In 1 (9%) case, the results of image-based simulation and the standard approach were inconsistent, where ablation outside the estimated target region was associated with acute success.

Conclusions: The image-based simulation can be used to estimate potential ablation targets of scar-related VT. The image-based simulation may be a powerful noninvasive tool for preprocedural planning of ablation procedures to potentially reduce the procedure time and complication rates.

Keywords: 3-D; 3-dimensional; Cardiac MRI; Catheter ablation; Computer simulation; ECG; EPS; HZ; ICD; Image-based simulation; LGE; LV; MI; MRI; SI; VT; Ventricular arrhythmia; electrocardiogram/electrocardiographic; electrophysiology study; heterogeneous zone; implantable cardioverter-defibrillator; late gadolinium enhancement; left ventricular; magnetic resonance imaging; myocardial infarction; signal intensity; ventricular tachycardia.

Figure 1. Study workflow

The patients referred for VT ablation (n=13) underwent pre-ablation MRI, which was processed to provide the heart and infarct geometry (red – scar, yellow - HZ), and estimated myofiber orientation (“Image-based Simulation”). These geometrical data were incorporated into mathematical simulation of VT to estimate potential target regions. Patients underwent an invasive electrophysiology study (EPS, n=13) and ablation (“Standard Approach”, n=11) using biplane X-ray fluoroscopy (RAO, right anterior oblique view; LAO, left anterior oblique view) and 3-D electroanatomical mapping (CARTO, Biosense Webster, Diamond Bar, California). Ablation lesion locations were recorded in 3-D space, and were compared with the target regions estimated by simulation. The study was retrospective but was conducted in a double-blind fashion, where the procedure operator was blinded to the simulation results, and the person who performed image processing and simulation was blinded to the clinical results.

Figure 2. Comparison between image-based simulation and standard approach

Each row represents a different patient (a, b and c). The Simulation column shows VT with an isochrone map of activation based on image-based simulation. Green arrows indicate wave propagation of macro-reentry circuits. Lines of conduction block are indicated in blue. The Electrophysiology study (EPS) column shows the 12-lead electrocardiogram (ECG) of inducible VTs from the standard approach. The Ablation column shows the 3-D CARTO map with a color-coded voltage map (purple – normal myocardium, blue, green and yellow – infarct border zone, red – scar) from the standard approach. Red circles represent the ablation sites. The size of the circles does not reflect the size of ablation lesions. The MRI column shows pre-ablation MRI with infarct geometry (orange – scar, yellow – HZ, gray – non-infarct myocardium). The lines of conduction block (blue lines) from the image-based simulation and the ablation sites (red circles) from the standard approach are co-registered on the heart geometry. The Estimated target region column shows a potential target region (green area) estimated from the image-based simulation. The shortest possible line of ablation that spans the target region (i.e. narrowest width of the isthmus) is indicated in cyan. The ablation sites that fell within the estimated ablation target (green area) are indicated by yellow circles. All three simulation results in this figure (patient a, b and c) show a figure-of-eight pattern, and are consistent with the 12-lead ECG of the clinical VT. The scales of the 12-lead ECG in the Electrophysiology study column is 100mm/s (patient a and b), and 25mm/s (patient c).

Figure 3. Comparison between image-based simulation and standard approach (continued)

The figure structure is the same as in Figure 2. The first two simulation results in this figure (patient a and b) show a figure-of-eight pattern, and the last simulation result (patient c) show a unidirectional circus movement pattern. All simulation results are consistent with the 12-lead ECG of the clinical VT. The scale of the 12-lead ECG in the Electrophysiology study column is 100mm/s (patient a, b and c).

Figure 4. Comparison between image-based simulation and standard approach (continued)

The figure structure is the same as in Figure 2. All three simulation results in this figure (patient a, b and c) show a unidirectional circus movement pattern, and are consistent with the 12-lead ECG of the clinical VT. The scale of the 12-lead ECG in the Electrophysiology study column is 100mm/s (patient a, b and c).