ACUTE AND LONG-TERM EFFECTS OF CONSECUTIVE RADIOFREQUENCY APPLICATIONS ON CONDUCTION PROPERTIES OF THE SUBEUSTACHIAN ISTHMUS IN TYPE-I ATRIAL-FLUTTER

Effects of Atrial Flutter Ablation. Introduction: Bidirectional conduc tion block at the subeustachian isthmus predicts long-term efficacy of atrial flutter ablation, Limited data are available on the incidence and outcome of minor conduction changes such as unidirectional or inco mplete block. This prospective study sought to systematically assess d iscrete acute and long-term alterations of bidirectional conduction pr ior to a complete conduction block, Methods and Results: In 41 patient s,vith type I atrial flutter, pulse propagation through the subeustach ian isthmus during low lateral and proximal coronary sinus pacing was documented and analyzed following each consecutive radiofrequency (RF) application, In cases of altered conduction properties and noninducib ility of atrial flutter, patients were followed-up for 12 months. Thre e sets of results were found, First, following RF application, 23 pati ents presented a progressive conduction delay prior to a complete cond uction block. Second, RF application did not always affect countercloc kwise and clockwise conduction simultaneously or to the same extent. I n 13 patients, an initial alteration of counterclockwise conduction wa s present before an alteration of clockwise conduction; in 5 patients, clockwise conduction was primarily affected. Third, the recurrence ra te of typical atrial flutter was 9% (2/22) in patients with a complete bidirectional conduction block, 54% (7/13) in patients with unidirect ional conduction block, and 100% (6/6) in patients with sole bidirecti onal conduction delay. Conclusion: In 50% of the patients, consecutive RF applications resulted primarily in a progressive conduction delay rather than a sudden conduction block, Since counterclockwise and cloc kwise conduction were not always affected simultaneously or to the sam e extent, lateral as well as septal pacing is recommended for improvem ent of bidirectional conduction block, Normalization of primarily alte red conduction and, therefore, recurrence of atrial putter are high in all patients without bidirectional block.