Does Rapid Atrial Pacing Influence Left Atrial Activation Time and Pattern in Patients with Atrial Fibrillation?

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Background: Reentry is considered to play an important role in maintaining AF, in which anatomical and/or functional disorder of impulse conduction is required. We hypothesized that LA conduction is partly and/or globally delayed in response to increases in the rate, especially in those having large LA. Methods: Eighteen patients undergoing PV antrum isolation were included (55±7 years old, paroxysmal/persistent=16⁄2). During right atrial pacing with 100 bpm (RA-100) and 200 bpm (RA-200) LA activation maps were constructed using NavX (449±70 sampling points/map). Rate-responsive changes in LA activation were evaluated by measuring activated surface areas at 30 ms and 40 ms after beginning of LA activation (Area-30 and Area-40), and LA total activation time (TAT). The changes were further analyzed with respect to LA volume, which was measured using 3D-CT. Results: LA volume, ranging from 46 to 162 ml (mean=79±28 ml), was well correlated with the TAT during RA-100. There were, however, no significant rate-responsive prolongations in TAT (66±10 ms vs. 67±10 ms), Area-30 (32±6 cm2 vs. 31±5 cm2) and Area-40 (43±6 cm2 vs. 41±5 cm2). The LA volume did not correlate with rate-responsive changes in any parameters. Increase in pacing rate did not affect LA activation pattern in any patient. Conclusion: Rate-responsive changes in the LA conduction time and pattern were not observed in the range of 100 to 200 bpm, irrespective of LA volume.