Fluctuation in autonomic tone is a major determinant of sustained atrial arrhythmias in patients with focal ectopy originating from the pulmonary veins

Introduction: This study was designed to analyze dynamic changes in autonom ic tone preceding the onset of sustained atrial arrhythmias in patients wit h focal atrial fibrillation (AF) to determine why patients with frequent di scharge from the arrhythmogenic foci develop sustained AF. Methods and Results: Holter tapes from 13 patients (10 men and 3 women; mea n age 53 +/- 5 years) with paroxysmal "lone" AF (mean 18 +/- 13 episodes pe r week) and a proven focal origin (pulmonary veins in all cases) were analy zed. A total of 38 episodes of sustained AF (>30 min) were recorded and sub mitted to frequency-domain heart rate variability analysis, Six periods wer e studied using repeated measures analysis of variance: the 24-hour period, the hour preceding AF, and the 20 minutes before AF divided into four 5-mi nute periods, A significant increase in high-frequency (HF, HF-NU) componen ts was observed during the 20 minutes preceding AF (P = 0.003 and 0.002, re spectively), together with a progressive decrease in normalized low-frequen cy (LF-NU) components (P = 0.035). An increase in LF/HF ratio followed by a linear decrease starting 15 minutes before sustained AF also was observed, indicating fluctuations in autonomic tone, with a primary increase in adre nergic drive followed by a marked modulation toward vagal predominance imme diately before AF onset. Conclusion: In patients with focal ectopy originating from the pulmonary ve ins, sustained episodes of atrial arrhythmias are mainly dependent on varia tions of autonomic tone, with a significant shift toward vagal predominance before AF onset.