Necessity for Biatrial Ablation to Achieve Bidirectional Cavotricuspid Isthmus Conduction Block in a Patient Following Senning Operation

We report the case of a 28-year-old male patient with a 17-year history of recurrent symptomatic atrial tachyarrhythmia following Senning operation for transposition of the great arteries. Biatrial electroanatomic mapping and entrainment mapping revealed counterclockwise peri-tricuspid annulus reentry in which cavotricuspid isthmus tissue in both systemic and pulmonary venous atria was involved. Linear ablation of the cavotricuspid isthmus in the pulmonary venous atrium terminated the tachycardia but did not block the isthmus conduction, and the tachycardia was reinduced. Bidirectional isthmus conduction block could be achieved only after additional linear ablation targeting the cavotricuspid isthmus tissue in the systemic venous atrium. We conclude that biatrial ablation may be necessary in order to achieve bidirectional isthmus block and prevent tachycardia recurrence in some patients following Senning or Mustard operation.