Background: Type I atrial flutter (AF) is a supraventricular tachycardia that is notoriously disabling and resistant to antiarrhythmic drugs. The introduction of an effective non-pharmacologic technique, such as radiofrequency catheter ablation (RF), opened new therapeutic prospects for the management of this arrhythmia. The aim of our study was to evaluate the long-term efficacy of atrial flutter RF using a successful procedure marker of bi-directional conduction block in the isthmus.
Methods: In the last consecutive 50 patients (pts) who underwent RF procedure for AF at our Center (46 pts during spontaneous or induced AF and 4 in sinus rhythm) after the successful interruption of AF we performed the usual reinduction attempts and well atrial pacing from 2 sites in the right atrium (in 18 pts before and after RF and in 32 only after RF). The sites of pacing were site 1: low lateral right atrium (LRA); site 2: proximal coronary sinus (PCS). The 50 pts consisted of 13 females, 37 males with a mean age of 62.5 +/- 9.7 years (35-83). The end-point for the procedure was: 1) abrupt interruption of AF; 2) inability to reinduce AF; 3) recognition of atrial activation sequence during pacing in LRA and in PCS compatible with conduction block in the isthmus.
Results: The RF was successful in terminating AF in all pts after 11 +/- 7 applications of energy. After ablation, sustained AF was no longer inducible by atrial pacing. After RF, during pacing in sinus rhythm from LRA, the lower septum and PCS presented a delayed activation after the His region. Similarly, during pacing from PCS after ablation, the atrial activation sequence was modified: the low lateral right atrium was now activated by a single front after the high lateral atrium. No acute complications were noted in any pts during or after procedure. AF recurred in 9 pts. Four pts now present chronic atrial fibrillation. The mean follow-up period is 14.8 +/- 8 months. All the patients were discharged without antiarrhythmic therapy.
Conclusions: The mechanism of successful ablation is the bi-directional conduction block in the isthmus with the evidence of the changes in the right atrial activation sequence during atrial pacing in sinus rhythm in LRA and in PCS before and after RF.