Abstract 2646: Electrophysiologic And Pharmacologic Characteristics Of Focal Right Atrial Tachycardias
Background: It has been recently reported that the majority of focal right atrial tachycardias (ATs) have fractionated electrograms near the site of successful ablation. This has been interpreted as indirect evidence for microreentry as the basis for these arrhythmias. To clarify this issue, we sought to characterize the electrogram properties at the successful ablation sites in a consecutive series of focal right ATs.
Methods: Thirty-six consecutive patients (22 M; 58 ± 17 yrs) who presented for catheter ablation of focal right AT are included in this series.
Results: The sites of AT origin were as follows: 21 arose from the tricuspid annulus (TA), including the region of the Triangle of Koch, 10 from the crista terminalis (CT), and 5 from other right atrial sites. Ablation was attempted in 35 of 36 ATs (one was deferred due to proximity to the AV node). Ablation was successful in 32 of 35 patients (91%). Adenosine (8.2 ± 3.9 mg) was administered to 35 ATs; 32 terminated, and 3 were transiently suppressed. Electrogram width at the successful ablation site was 51 ± 19 ms (12.5 ± 3.9% of AT cycle length). Only five of these electrograms had widths over 15% of the AT cycle length, and were deemed as sites with fractionated electrograms: 4 from the CT, 1 from the TA. Overall, mean electrogram amplitude at ablation sites was 0.47 ± 0.31 mV. Mean electrogram amplitude in the patients with fractionated electrograms at ablation sites was lower than that of patients without fractionated electrograms (0.27 vs 0.50 mV; p = 0.04). The mean AT cycle length overall was 411 ± 75 ms. There was no significant difference between these groups with respect to AT cycle length (408 vs 412 ms).
Conclusions: Electrophysiologic and electrogram characteristics of right ATs typically do not demonstrate fractionation, with the possible exception of some CT sites. These data do not support the hypothesis that cellular uncoupling (fractionation) is the basis for microreentry as a mechanism of the majority of focal right ATs.