Characteristics of frequency content of atrial signal-averaged electrocardiograms during sinus rhythm in patients with paroxysmal atrial fibrillation

To clarify the characteristics of the frequency content of atrial signal-averaged electrocardiograms (ECGs) during sinus rhythm in patients with paroxysmal atrial fibrillation, P wave-triggered signal-averaged ECGs were recorded in 28 patients with and 34 control patients without paroxysmal atrial fibrillation. Fast Fourier transform analysis was performed on the 100-ms segment starting 75 ms before the end of the P wave. An area ratio (AR50) was calculated by dividing the area under the spectrum curve between 20 and 50 Hz, multiplied by 100, by the area between 0 and 20 Hz. Magnitude ratios (MR20, MR30, MR40and MR50) were calculated by dividing the magnitude at 20, 30, 40 and 50 Hz, respectively, multiplied by 100, by the maximal magnitude of the entire signal.AR50was significantly greater in patients with than without paroxysmal atrial fibrillation (62.3 ± 34.2 vs. 42.4 ± 18.4). MRM and MR30were also significantly greater in patients with than without paroxysmal atrial fibrillation (MR2076.1 ± 15.2 vs. 60 ± 20.2; MR3041 ± 18.8 vs. 26.6 ± 14.4), although no significant differences in MR40or MR50were observed between the two patient groups. The difference in MR30between groups remained significant even after taking into account the presence of organic heart disease.It is concluded that, irrespective of the presence of organic heart disease, the terminal portion of the P wave contained significantly more components in the 20- to 50-Hz range, especially around 30 Hz, in patients with than in patients without paroxysmal atrial fibrillation. These results suggest that frequency analysis could characterize atrial signal-averaged ECGs of patients at risk for paroxysmal atrial fibrillation