A 43-year-old woman had undergone patch closure operation for
atrial septal defect 27 years ago. She was referred to our hospital for evaluation of frequent palpitations since 1 year ago. Electrophysiological study was performed with recording of the coronary sinus, His bundle, and low lateral right free wall electrography utilizing a steerable duo-decapolar
electrode catheter(Livewire, Daig).
Supraventricular tachycardia with cycle length alternation of 300 and 320 msec similar to
atrial flutter was reproducibly provoked by burst pacing from the coronary sinus. During the
supraventricular tachycardia, abnormal atrial potentials occurred in the low lateral right free wall region with very low amplitude and splitting potentials. The cycle length alternation of the
supraventricular tachycardia depended on the occurrence of the splitting potentials, that is, the splitting potentials were present during the
supraventricular tachycardia with a long cycle and the splitting potentials were absent during the
supraventricular tachycardia with a short cycle. This phenomenon suggested that the splitting potentials resulted from 2:1 functional intra-atrial local conduction block. In addition, during sinus rhythm the abnormal electrograms revealed fractionated activity. Thus, these findings strongly imply that the
supraventricular tachycardia is due to a macro-reentrant right atrial
tachycardia utilizing an anatomical obstacle caused by the
atrial septal defect operation as a central area, namely incisional reentrant atrial
tachycardia. Three-dimensional electroanatomical mapping using the CARTO system(Biosense-Webster) was conducted to investigate whether the low lateral right free wall area possessed the critical isthmus essential to the reentry circuit. Electroanatomical mapping revealed that the very low amplitude potentials and the splitting potentials corresponded to the
scars and the functional conduction block area detected by mapping using the multipolar
catheter, respectively. According to the propagation mapping, the incisional reentrant atrial
tachycardia slowly conducted the channel created by multiple neighboring
scars clockwise and the alternation of the
tachycardia cycle length was dependent on the development of the functional local intra-atrial conduction block within the channel. An approximately 1.5 cm successful linear lesion was created by
radiofrequency catheter ablation to transect the isthmus based on the electroanatomical mapping findings. Afterwards, the incisional reentrant atrial
tachycardia could not be induced by burst stimuli from the coronary sinus even under administration of
isoproterenol. The use of three dimensional electroanatomical mapping(CARTO system) to evaluate the reentry circuit after the detection of abnormal potentials by using multipolar
catheter in advance is a very useful method to determine optimal target site of ablation for a patient with incisional reentrant atrial
tachycardia.