Relationship between the spectral characteristics of atrial fibrillation and atrial tachycardias that occur after catheter ablation of atrial fibrillation.

Background: During catheter ablation of complex fractionated atrial electrograms, persistent atrial fibrillation (AF) may convert to an atrial tachycardia (AT).
Objective: The purpose of this study was to investigate the possible mechanisms of AT by examining the spectral and electrophysiologic characteristics of AF and ATs that occur after catheter ablation of AF.
Methods: The subjects of this study were 33 consecutive patients with persistent AF who had conversion of AF to AT during ablation of AF (group I) and 20 consecutive patients who underwent ablation of persistent AT that developed more than 1 month after AF ablation (group II). Spectral analysis of the coronary sinus (CS) electrograms and lead V(1) was performed during AF at baseline, before conversion, and during AT. The spatial relationship between the AT mechanism and ablation sites was examined.
Results: A spectral component with a frequency that matched the frequency of AT was present in the baseline periodogram of AF more often in group I (52%) than in group II (20%, P = .02). Ablation resulted in a decrease in the dominant frequency of AF but not in the frequency of the spectral component that matched the AT. There was a significant direct relationship between the baseline dominant frequency of AF and the frequency of AT in the CS in group I (r = 0.76, P <.0001) but not in group II (r = 0.38, P = .09). ATs were macroreentrant in 64% and 60% of patients in groups I and II, respectively (P = .8). The AT site was more likely to be distant (>1 cm) from AF ablation sites in group I (70%) than in group II (35%, P = .007).
Conclusion: The findings of this study suggest that ATs observed during ablation of AF often may be drivers of AF that become manifest after elimination of higher-frequency sources and fibrillatory conduction.