We have examined 24 hours ECG Holter recordings of 22 patients without any organic heart disease and with recurrent episodes of paroxysmal atrial fibrillation (PAF) to check the possible sympatho-vagal influence on spontaneous initiation. Patients were divided into 3 groups according to average heart rate (HR) during the 24 hours recording and to the mode of onset of the arrhythmia: sympathetic (only diurnal episodes, HR greater than or equal to 75 b/min before the onset of the episode, average 24 hours HR greater than or equal to 80 b/min, progressive or sudden shortening of sinusal cycle before the onset), vagal (only nocturnal episodes, HR less than or equal to 60 b/min before the onset, average 24 hours HR less than or equal to 60 b/min, progressive or sudden lengthening of sinusal cycle before the onset of the episode) or "others" who did not show the aforementioned characteristics
