Non-invasive assessment of magnitude and dispersion of atrial cycle length during chronic atrial fibrillation in man

Aims Atrial fibrillation cycle lengths can be assessed from right precordial ECG leads and the unipolar oesophageal ECG using a non-invasive method called Frequency Analysis of Fibrillatory EGG. The purpose of this report is to present the results from application of this method in a large group of patients with long-term atrial fibrillation and to examine the differences between patients with 'coarse' and 'fine' atrial fibrillation. Methods and Results Simultaneous 15 min recordings from V-1, V-2 and an oesophageal lead at a position behind the posterior atrium were obtained in 28 patients, aged 41 to 78 years, with long-term (>1 month) atrial fibrillation. In each lead, using the time averaging technique, the QRST complexes were suppressed. Thereafter, the frequency distribution of the residual ECG was estimated by means of Fast Fourier Transform. In the 3-12 Hz range of each lead, the dominant atrial cycle length, the power maximum and the spectral width were calculated. In 26 patients (93%), frequency spectra in the 3-12 Hz range could be obtained. The dominant atrial cycle length ranged from 120 to 175 ms, mean 150 +/- 16 (SD) ms in V-1, and from 120 to 190 ms, mean 150 +/- 16 in an oesophageal lead (ns). The absolute difference in the dominant atrial cycle length between V-1 and the oesophageal lead was 10.4 +/- 7.7 ms. There was no significant difference in the dominant atrial cycle length in V-1 between patients with coarse and fine atrial fibrillation. The power maximum in V-1 was significantly greater in patients with coarse compared to fine atrial fibrillation (P = 0.01). The spectral widths ranged from 10 to 55 ms and demonstrated significantly higher mean values in lead V-2 compared to V-1 (P = 0.001). Compared to V-1, the mean values tended to be smaller in the oesophageal lead (P = 0.05). Conclusions Using the Frequency Analysis of Fibrillatory ECG method, the dominant atrial cycle length, power maximum and spectral width can be estimated from the frequency spectra in the majority of patients with atrial fibrillation. Spatial dispersion of the dominant atrial cycle length occurs in some patients and may be an important proarrhythmic marker. The distinction between coarse and fine atrial fibrillation cannot be used as a marker of the atrial cycle length.