FREQUENCY-ANALYSIS OF HUMAN ATRIAL-FIBRILLATION USING THE SURFACE ELECTROCARDIOGRAM AND ITS RESPONSE TO IBUTILIDE

This study assesses a technique for quantifying the frequency spectrum of atrial fibrillation (AF) using the surface electrocardiogram. Elec trocardiographic recordings were obtained in 61 patients during AF. Af ter bandpass filtering, the QRST complexes were subtracted using a tem plate-matching algorithm. The resulting fibrillatory baseline signal w as subjected to Fourier transformation and displayed as a frequency po wer spectrum. These frequency spectra were compared to direct measurem ents from the right atrium and coronary sinus in 35 patients undergoin g electrophysiologic study, The clinical use of this technique was exp lored by correlating fibrillatory frequency with the behavior of the a rrhythmia in 26 patients referred for cardioversion. The electrocardio graphic frequency spectrum during AF was characterized by a single pea k that varied widely between patients (range 228 to 480 beats/min). Th ere was a strong correlation between electrocardiographic peak frequen cy and that measured in the right atrium and coronary sinus (r = 0.79 to 0.98, p<0.0001). Episodes of AF that terminated in <5 minutes had a lower frequency than those that persisted >5 minutes (324 +/- 36 vs 4 02 +/- 78 beats/min, p = 0.001). Chronic AF (<3 months in duration) ha d a lower frequency than chronic AF (present >3 months) (336 +/- 48 vs 408 +/- 60 beats/ min, p = 0.012). Fibrillation frequency wets an acc urate predictor of conversion with ibutilide. Success rate was 100% in patients with peak frequency <360 beats/min versus 29% in patients wi th frequencies greater than or equal to 360 beats/ min (p = 0.003). Au tomatic analysis of the frequency content of the fibrillatory baseline on the surface electrocardiogram accurately reflects the average rate of AF. This measurement correlates with the clinical pattern of the a rrhythmia and predicts the response to administration of ibutilide. (C ) 1998 by Excerpta Medica, Inc.