Non-invasive assessment of fibrillatory activity in patients with paroxysmal and persistent atrial fibrillation using the Holter ECG

Objective: Automatic analysis of the frequency content of the fibrillatory baseline on the surface ECG accurately reflects the average rate of atrial fibrillation (AF). This frequency measurement correlates with the behavior of AF and predicts the response to administration of ibutilide, a new antia rrhythmic drug. Neither the temporal pattern of fibrillatory frequency in s pontaneous paroxysmal or persistent AF, nor its response to chronic antiarr hythmic medication has been studied so far. Methods and Results: Holter ECG recordings were made in 20 patients during AF. One minute ECG segments wer e selected for analysis. The frequency content of the fibrillatory baseline was then quantified using digital signal processing. After high-pass filte ring, the QRST complexes were subtracted using a template matching algorith m. The resulting fibrillatory baseline signal was subjected to Fourier tran sformation, displayed as a frequency power spectrum and the peak frequency (f) was determined. In 11 patients (7 male, 4 female, age 62 +/- 10 years) 31 paroxysmal AF episodes were analyzed. Duration ranged from 1 min to 665 min (115 +/- 175 min). Initial mean peak f measured 5.1 +/- 0.7 Hz (range 3 .9 to 6.9 Hz). There was a positive correlation between f and AF duration ( R = 0.53, p = 0.002). AF of less than 15 min duration (n = 13) showed a low er f (4.8 +/- 0.6 Hz) when compared with longer lasting episodes (n = 18, 5 .3 +/- 0.7 Hz, p = 0.03). In short AF episodes f was constant, whereas in l onger-lasting episodes f increased to 5.8 +/- 0.5 Hz (p < 0.001) within 5 m in. In 9 patients (9 male, age 58 +/- 8 years) with persistent AF oral anti arrhythmic drugs (amiodarone n = 5, sotalol n = 3, flecainide n = 1) were g iven prior to electrical cardioversion for prophylaxis of AF recurrence. Fr equency measurements were obtained at baseline and 3 to 5 days after initia tion of drug administration. At baseline mean f measured 6.9 +/- 0.4 Hz. Fr equency was reduced by antiarrhythmic drugs to 5.8 +/- 0.4 Hz (p < 0.001). Conclusions: (1) The duration of paroxysmal AF episodes can be predicted us ing spectral analysis of ECG recordings of AF episodes. (2) An increase in fibrillatory frequency is associated with AF persistence. (3) This techniqu e can be used to monitor the response to antiarrhythmic medication. (C) 199 9 Elsevier Science B.V. All rights reserved.