A particularly atypical case of atypical flutter in a patient after a Mustard repair for d-transposition of the great arteries

Despite the fact that peri-tricuspid annular flutter is common post Mustard repair for dextro-transposition of the great arteries (d-TGA), peri-mitral annular flutter has not been reported. We report the first case of peri-mitral annular flutter post Mustard repair in a patient who also had atrioventricular re-entry utilising a left sided accessory pathway. Both of these arrhythmias were successfully treated with ablation therapy. We discuss the challenges in mapping atrial flutter post Mustard repair, approaches to safely ablate a mitral isthmus line in these patients and the reasons why peri-mitral flutter is an uncommon arrhythmia in this setting.