An unmappable ventricular tachycardia in the arrhythmogenic right ventricular cardiomyopathy: elucidation of critical isolated delayed components with high-resolution electroanatomical mapping.

Unmappable ventricular tachycardia (VT) is a challenge in the management of arrhythmogenic right ventricular cardiomyopathy (ARVC). We report a feasible strategy for a curative ablation. In the present case with ARVC, the clinical VT showed a single morphology of left bundle branch block with inferior axis. Neither activation mapping nor entrainment mapping could be done because of instability of the haemodynamics. Furthermore, pace mapping could not be obtained due to electrically unexcitable scars covering with the RV. We found isolated delayed components (IDCs) in the diastolic phase recorded within the scar areas. Electroanatomical mapping (CARTO) with tiered decreasing voltage definition revealed that IDCs were delineated on the narrow conducting channels along or between the complete scars (amplitude < or =0.1 mV). Isolated delayed components on the narrow channels were targeted under the guidance with CARTO. After 11 radiofrequency applications, the clinical VT was eliminated. Moreover, epsilon waves recorded on the 12-lead electrocardiogram disappeared. No ventricular tachyarrhythmia was recognized at 6-month follow-up. Isolated delayed component ablation with high-resolution CARTO map was feasible and provided a curative approach in the treatment of an unmappable VT in ARVC.