Modification of the substrate for maintenance of idiopathic human atrial fibrillation: efficacy of radiofrequency ablation using nonfluoroscopic catheter guidance.

BACKGROUND: Catheter ablative techniques to modify the substrate to maintain atrial fibrillation (AF) require the creation of continuous radiofrequency current-induced ablation lines. This study was designed to assess the efficacy and safety of nonfluoroscopic mapping in this setting. METHODS AND RESULTS: A total of 45 consecutive patients with idiopathic AF were studied. The first 13 underwent ablation confined to the left atrium by creating a circular line isolating the pulmonary vein ostia and a second line connecting the former with the mitral annulus. Subsequently, 12 of these patients underwent a procedure confined to the right atrium (RA), where attempts were made to create an isthmus line between the inferior vena cava and the tricuspid annulus, an anterior line connecting the tricuspid annulus with the superior vena cava, and an intercaval line between the ostia of the inferior and superior venae cavae. In the last 32 patients, only the RA approach was performed. Technical difficulties prevented the creation of the intended left atrial line pattern: all patients experienced recurrences. A 100% recurrence rate was also observed after subsequent RA ablation, despite creation of a complete line pattern in 4 of 12 patients. Of the final 32 patients, AF recurred in 94%; a complete ablation line pattern had been achieved in 18 patients (56%), 16 of whom had recurrences. CONCLUSIONS: The electroanatomically-guided creation of extended radiofrequency current lesions is technically feasible only in the RA. However, procedural success in the RA does not suppress recurrences of AF in the majority of patients.

Nonfluoroscopic endocardial catheter mapping of atrial fibrillation.

The treatment of drug-refractory atrial fibrillation (AF) remains one of the unsolved problems in cardiology. Surgical interventions have demonstrated that AF can be prevented by multiple incisions within both atria. Recently, this strategy has been translated into a catheter procedure. So far, the ablation approach is not based on individual electrophysiologic data, but constitutes only an anatomic approach. Further insight into the spatial and temporal distribution of the local electrograms during AF is needed. Electroanatomic maps acquired by sequential mapping over 45 seconds at each site during AF in six patients with paroxysmal AF were analyzed off-line. Electrograms were sampled at a mean of 36 +/- 12 sites in the left atrium of each patient. A total of 217 sites were sampled, of which 27.3% (59) represented type A (regular) AF, 9.7% (21) represented type B (totally irregular), and 63.1% (137) represented type C (mixture of type A and B) electrograms. The distribution was analyzed in 20 different segments of the left atrium, and a significantly higher incidence of type A electrograms was found in area 3 (upper lateral pulmonary vein) than at all other sites (P < 0.005). This observation needs further confirmation before any conclusion with regard to catheter ablation can be drawn, particularly because the analysis was based on bipolar recordings from a 4-mm tip electrode.