Ablation for unmappable ventricular tachycardia in a patient with complete transposition of the great arteries who underwent Rastelli repair.

Catheter ablation (CA) of ventricular tachycardia (VT) after repair of congenital heart disease may be difficult because of complex anatomy and sometimes unmappable VT. Here, we report a 41-year-old woman with successful CA of unmappable VT in a patient with complete transposition of the great arteries after Rastelli repair. Clinical VT was induced by programmed electrical stimulation, when the mapping catheter was placed at the high anterior right ventricular outflow tract (RVOT). During VT, the local potential at the high anterior RVOT under the right ventricle (RV) - pulmonary artery (PA) conduit was equal to that at the timing of onset of QRS. The VT was unmappable because the hemodynamics deteriorated. Pace mapping was also tried at the aortic cusp and the left ventricular outflow tract (LVOT). Fractionated potential during sinus rhythm was observed at the noncoronary cusp, and the paced QRS morphology at this site was similar to that of the clinical VT, with a delay of 55 ms from pacing to the onset of QRS. However, mapping at the LVOT was impossible due to the difficulty of catheter manipulation. Radiofrequency energy was successfully applied at the noncoronary cusp and the high anterior RVOT under the RV-PA conduit. <Learning objective: This report is a rare case of successful catheter ablation of unmappable ventricular tachycardia (VT) in a patient with complete transposition of the great arteries after Rastelli repair. The VT was unmappable because of intolerable hemodynamics. However, we could speculate the exit or isthmus of the VT by pace mapping or local potential and eliminate the VT.>.