Attenuating Effects of Anti-Arrhythmic Agents on Changes in Fibrillation Cycle Length in Very Early Phase Paroxysmal Atrial Fibrillation-Spectral Analysis of Fibrillation Waves in Surface ECG-

Background: Antiarrhythmic agents may affect electrical remodeling but little is known regarding clinical cases. We evaluated fibrillation cycle length (FCL) of atrial fibrillation (AF) by spectral analysis of fibrillation waves (FW) in surface ECG for patients on antiarrhythmic agents. Methods and Results: 18 patients (14 males; 58 +/- 2 year-old) with paroxysmal AF (pAF) lasting over 30 minutes recorded by Holter ECG were enrolled. FW was purified by subtraction of QRS-T, and calculated by fast Fourier transformation analysis. FCL was defined as reciprocal of mean peak frequency. Temporal variability was expressed as FCL coefficient of variation (FCL-CV). FCL and FCL-CV were calculated at 0, 1, 5, 10, and 30 minutes after the onset of AF. We evaluated three groups: control group (6 patients with no medication), class I group (6 patients with pilsicainide or flecainide), and bepridil group (6 patients with bepridil). FCL showed quick-shortening at first minute in control group (p < 0.001), and relatively slow-shortening in class I group. In bepridil group, FCL was not significantly shortened within 30 minutes. FCL-CV did not change, but was significantly larger in bepridil group. Conclusions: FCL of pAF showed significant shortening in control group, but FCL shortening was suppressed and FCL-CV was larger in bepridil group. This result may indicate the specific effect of bepridil for electrical changes in early phase of pAF.