Changes of autonomic tone before the onset of paroxysmal atrial fibrillation

The relationship between autonomic nerve system and the onset of paroxysmal atrial fibrillation (PAF) is still controversial. Furthermore, no prior st udies have compared heart rate variability (HRV) between PAF patients with (organic) or without (idiopathic) underlying cardiac diseases. The purpose of this study was to assess the alteration of autonomic tone by analyzing H RV immediately before the onset of atrial fibrillation. This study included 57 patients (M/F: 34/23, 66+/-22 years) with frequent attacks of PAF. All cases underwent 24-h ambulatory Holter monitoring; each patient had one or more episodes of sustained PAF (>30 a). A period of sinus rhythm 40 min was allowed for accurate assessment of HRV over these periods. Spectral HRV wa s expressed as low (0.04-0.15 Hz) and high (0.15-0.40 Hz) frequency compone nts (LF, HF), and L/H ratio at 2-min intervals over a 40-min period before the onset of PAF. According to HRV, three subtypes were classified; onset o f PAF accompanied with increased HF component and decreased L/H ratio was d esignated as vagal type; decreased HF component and increased L/H ratio was designated as sympathetic type, and the other episodes which did not belon g to vagal or sympathetic type were designated as non-related type. In grou p I (idiopathic PAF, n=30): 63 episodes of PAF were found and vagal type wa s predominant (41/63, 63.5%); HF increased significantly before the onset o f AF. In group IT (organic PAF, n=27): 58 episodes of PAF were found and sy mpathetic type was predominant (39/58, 67.2%); L/H ratio increased before A F onset. None of the three subtypes showed significant circadian distributi ons in group I and II patients. Changes of HRV before the onset of PAF were not universal; most of the patients with idiopathic PAF were vagal depende nt and most of the patients with organic PAF were sympathetic dependent. (C ) 1998 Elsevier Science Ireland Ltd. All rights reserved.