Onset mechanism of paroxysmal atrial fibrillation detected by ambulatory Holter monitoring.

AIMS The aim of this study was to evaluate the mechanisms of induction of paroxysmal atrial fibrillation (PAF) by analysis of its onset recorded on Holter monitoring (HM). METHODS AND RESULTS One hundred and seven HM were evaluated in 90 patients (mean age 67.7, cardiac disease in 31.1%), with one or more self-terminating episodes of PAF, lasting >or=30 s. Two hundred and thirty-three episodes of PAF were detected. A triggering premature atrial complex (PAC) was present in 222/233 episodes (95.3%); 118/233 episodes were preceded by a bradyarrhythmic event (BE) or a post-extrasystolic pause (50.6%). According to the polarity of the ectopic P-wave, triggering PACs were left atrial origin in 74.3%, right atrial in 15.3%, not determined in 10.4% of cases. Coupling interval (CI) of triggering PACs was shorter in episodes preceded by BEs; it was shorter than that of non-triggering PACs. Frequency of PACs was significantly higher in the hour preceding the onset of PAF. During the day, three periods of higher frequency of PAF onsets were found from noon to 2 p.m., 6 p.m. to 2 a.m., and 4 a.m. to 6 a.m. Heart rate variability analysis showed a vagal prevalence in the 5 min preceding the onset of arrhythmia, both in the time and in the frequency domain. CONCLUSION Paroxysmal atrial fibrillation is generally triggered by a PAC, with left atrial origin in two-thirds of cases: CI and neuroendocrine balance are factors affecting the induction of the arrhythmia.