A confluent non-enhanced dark core on serial late gadolinium enhancement imaging after a moderator band-ventricular tachycardia ablation

A 77-year-old man underwent radiofrequency catheter ablation of incessant ventricular arrhythmias (VAs) originating from the right ventricular (RV) moderator band (MB). Activation mapping during the VAs exhibited a centrifugal pattern with the earliest activation site (EAS) on the RV septum. A local impedance (LI)-guided radiofrequency application targeting the EAS with a maximum power output of 50W successfully eliminated the VAs and resulted in an LI drop of up to 35 Ω. Late gadolinium enhancement magnetic resonance imaging (LGE-MRI) on the day after the ablation procedure demonstrated a confluent non-enhanced dark core on the RV septal portion of the MB. On the LGE-MRI two months after the procedure, the dark core region became contracted and instead the peripheral region surrounding the dark core exhibited a bright enhancement. The size of the dark core and peripheral enhanced regions on the LGE-MRI remained almost unchanged two months to two years after the procedure. He had no VA recurrences during a two-year follow-up period. Previous LGE-MRI studies reported that an ablated area within healthy ventricular myocardium exhibits a bright homogenous enhancement during the post-ablation chronic phase, while that within ventricular scar tissue exhibits a confluent non-enhanced dark core. This case suggested the presence of a dark core with a peripheral enhancement corresponding to the ablated area within the healthy myocardium of the RV-MB. LGE-MRI may be useful for accurately detecting RF ablation lesions on the RV-MB and visualizing the serial changes in the LGE-MRI characteristics from the post-ablation acute to chronic phases.