ALTERNATION IN THE FLUTTER WAVE MORPHOLOGY DURING RADIOFREQUENCY CATHETER ABLATION FOR COMMON ATRIAL-FLUTTER

A linear lesion created at the right atrial isthmus by radiofrequency current application can successfully eliminate common atrial flutter ( AF). The mechanism of unsuccessful cases has not yet been well delinea ted. This study sought to investigate the cause of unsuccessful cases of radiofrequency catheter ablation of AF. Sixty-six patients with ref ractory common AF were referred for radiofrequency catheter ablation. Radiofrequency current was applied to the right atrial isthmus between the inferior vena cava and tricuspid annulus or between the coronary sinus orifice and tricuspid annulus. In 5 (8%) of the 66 patients, a m orphological change of the flutter wave was observed in the 12-lead EC G concomitant with the change of the atrial excitation sequence during the delivery of radiofrequency energy without the termination of atri al flutter. In 8 (12%) patients, the morphology of the new AF wave, wh ich was provoked electrically after the termination of the original AF , was different, and the average flutter cycle length also differed in 3 cases (2%). The results of radiofrequency application could be misi nterpreted as unsuccessful when the occurrence of another, different t ype of AF has been overlooked following the elimination of the origina l AF during the radiofrequency catheter ablation procedure. It is poss ible that the flutter circuit can take an alternative pathway despite the complete conduction block at the right atrial isthmus.