SHORTCUT LINK BETWEEN THE FAST AND SLOW PATHWAYS AND THE MECHANISM OFCURE IN ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA BY CATHETER ABLATION

The mechanism of cure in AV nodal reentrant tachycardia (AVNRT) by cat heter ablation has not been fully clarified. We hypothesized that disr uption of a shortcut link between the fast and slow pathways is respon sible for the elimination of tachycardia. Results: AVRNT was eliminate d in 20 patients by catheter ablation. In five patients (25%; group I) slow pathway conduction disappeared 1 week after ablation. In six pat ients (30%; group II), the effective refractory period of the slow pat hway was prolonged by more than 50 ms (212 +/- 81 ms vs 340 +/- 81 ms; P < 0.05). In the remaining nine patients (45%; group III), there was no change in the refractory period (270 +/- 65 ms vs 273 +/- 74 ms), although tachycardia was not inducible. A shortcut link between the fa st and slow pathways was examined by comparing the A-H intervals over the slow pathway during the tachycardia and during atrial pacing at th e tachycardia cycle length. Prior to ablation, a shortcut link was ass umed in 1 of group I patients, 2 of group II patients, and 8 of group III patients. Of the 9 patients in whom the slow pathway was not impai red after ablation (group III), 8 patients were found to have a shortc ut link, while 8 of 11 patients with impairment of the slow pathway af ter ablation (groups I and II) had no shortcut link between the fast a nd slow pathways (P < 0.05). Conclusion: In patients with a shortcut l ink between the fast and slow pathways, slow pathway conduction itself does not need to be impaired to eliminate the AVNRT, whereas in patie nts without this shortcut link, slow pathway conduction must be impair ed.