Wideband 3D LGE is useful for identifying arrhythmogenic substrate for VT ablation in patients with CIEDs

Description of Clinical Presentation: A 74-year-old male with a history of arrhythmogenic cardiomyopathy and MRI conditional implantable cardioverter defibrillator (ICD) presented for evaluation following multiple ventricular tachycardia (VT) episodes. He previously underwent VT ablations targeting arrhythmogenic sites in the right ventricular outflow tract (RVOT), inferior and anterior RV walls, and peri-tricuspid annulus. His last ablation and ICD implantation was 5 years ago at another center, so prior imaging studies were not accessible. In the several months prior to presentation and despite oral amiodarone and mexiletine, he was admitted three times for sustained VT below his detection rate requiring cardioversion for the first two, and IV amiodarone for the most recent episode. A repeat VT ablation using pulsed field ablation (PFA) was recommended.

Diagnostic Techniques and Their Most Important Findings: Prior to VT ablation, the patient underwent wideband 2D and 3D late gadolinium enhanced (LGE) approximately 10 and 25 minutes after gadobutrol administration (0.2 mmol/kg) on a 1.5T MRI scanner (Avanto, Siemens). Wideband 3D LGE used a wideband (4 kHz) inversion-recovery RF pulse integrated into a stack-of-stars sequence with a 2D self-navigator for motion correction (1). Horos (Horos Project) was used for 3D LGE visualization by multiplanar reconstruction, and ADAS 3D (ADAS 3D Medical, Barcelona) was used for 3D LGE segmentation. Although scarring was difficult to appreciate on wideband 2D LGE, wideband 3D LGE identified localized enhancement in the basal anterior RV free wall extending into the RVOT (Figure 1), which precisely matched the site of earliest activation during non-sustained VT (left bundle superior axis, V4 transition) identified during electroanatomic mapping (Figure 2). Accordingly, consistent with the pre-procedural MRI findings, long and fractionated late potentials were observed in this region in sinus rhythm, and pace mapping over a broad area yielded a good morphologic match in 10 of 12 leads. Ablation using the Sphere 9 catheter with PFA resulted in complete elimination of the late potentials and suppression of frequent PVCs and NSVT. A total of 27 PFA applications were delivered to achieve complete RVOT substrate modification.

Learning Points from this Case: This case highlights the potential clinical utility of wideband 3D LGE in accurately identifying arrhythmogenic substrates and guiding VT ablation in patients with ICDs, in whom wideband 2D MRI may be limited by noise and partial volume averaging effects due to poor through-plane resolution.

Figure 1. 2D LGE vs 3D LGE cardiac MRI demonstrating hyperenhancement in basal anterior RV free wall extending into the RVOT
Figure 2. Comparison of 3D LGE and electroanatomic mapping (EAM) of the right ventricle with corresponding intracardiac electrograms at the RVOT, with long and fractionated late potentials (red arrow) before and after ablation. Left panels show 3D LGE-derived scar visualization (yellow arrows). Middle and right panels show corresponding voltage maps with and without ablation lesions (green tags)