The ablation of accessory pathways(APs) using radiofrequency(RF) energy has been establihed as a primary modality of treatment for atrioventricular reentranr tachycardia with probrn safety and high rate of success. However, the ablation of posteroseptal(PS) APs had been recognized as being more difficult to ablate than those in other location because of the complex three dimensional anatony of the posterior apace, and multifarious approaches have been proposed. We analyzed electrophysiologic characteristics and results of catheter ablation of 70 consecutive patients, who underwent RF ablation of PS APs with or without booster direct current(DC) shock.

Teh AP location was confirmed to be in the PS region, ablation was attepmted at the atrial aspect of the tricuspid annulus adjacent to the coronary sinus ostium, within the coronary sinus in couding middle cardiac vein, or underneath the mitral annulus close to the septum using retrograde transaortic approach if deemed necessory. A continuous, unmodulated sine wave radiofr-equency generator was used as the source of energy for ablation. The site was considered optimal for ablation when the electrogram obtained from the ablation catheter had one or more of the following characteristics : (1) short VA intervals with an A : V ratio of ≤1.0 amd discrete, high frequency potentials or fractionated electrograms between local atrial and ventricular de-flections(accessory pathway potential) ; (2) vrntricular activation occurred simultaneously with or earlier than the delta wave during sinus rhythm with manifest preexcitation ; and (3) atrial activation occurred simultaneously with or earlier than that recorded in the reference coronary sinus dlectrogram during retrograde AP conduction. ucceccful criteria was complete loss of anterograde and retrograed AP conduction.

Seventy consecutive patients(male 44, female 26) with PS APs underwent catheterablation. anifest preexcitation was present in 40 patients and concealed APs in 30. Two patients had double APs. AP conduction was successfully eleminated in 60 of 70 cases at initial attempt(success rate 85.7%). Successful ablation sites of 60 patients were as follows ; 29 at the left PS region, 14 at the margin of the coronary sinus ostium, 8 in the proximal portion of the coronary sinus, 6 at the ticuspid annulus, and 3 at the inferomedial portion of right atium. The mean shortest VA interval in successful group was shorter than that in failed group(85±19msec versus 100±22msec). ecurrence was noted in 8 patients(13.3%) during a mean follow-up period of 33.1±13.3 months. ive patients with recurrence and two patient of unsuccessful initial attempt underwent the second catheter ablation and 5 patients were successful. Complications occurred in 11 patients ; transient high degree AV block in 8, pneumothorax in 2, and transient cerebral ischemic attack in one patient.

These data suggested that posteroseptal APs could be ablated at the oeft sode or the right side PS region in similsr proportion. This series, even though it included learning period, showed slightly lower success rate(87.5%) than that of total APs success rate in our experience(90.8%). Therefore a firm grasp of the anatomic characteristic of the posterior space and meticulous mapping may facilitate the achievement of successful results in the ablation of porteroseptal accessory pathways.