Influence of the Direction of Conduction on the Dominant Frequency of Left Atrial Electrocardiograms During Sinus Rhythm in Patients with Atrial Fibrillation

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Background: Complex electrocardiogram morphologies (atrial fibrillation [AF] nests) in sinus rhythm (SR) recorded by frequency domain techniques can serve as a pathologic substrate for atrial fibrillation (AF). We sought to characterize any direction-dependent and rate-dependent changes in dominant frequency (DF) and high DF sites in the left atrium (LA) in patients with AF. Methods: Eight patients with AF were included in the study. A basket catheter with 64 electrodes was placed in the LA. Forty-eight bipolar electrocardiograms were recorded during SR and during pacing from the high right atrium (HRA), proximal coronary sinus (CS), and distal CS at various pacing rates, ranging from 600 ms to 250 ms. The frequency domain measures of LA bipolar electrocardiograms were compared during SR and HRA, proximal CS, and distal CS. Results: The DF was found to be higher during proximal CS and distal CS pacing than during SR. The percentage of high DF (>70 Hz) sites was higher during distal CS pacing than during SR. The various pacing rates applied during HRA, proximal CS, and distal CS pacing did not affect the DF values. Conclusion: DF of atrial electrocardiograms obtained during SR was influenced by the direction of conduction but not by the pacing rate.