Initiating mechanisms of paroxysmal atrial fibrillation

Background The understanding of the onset mechanisms of paroxysmal atrial fibrillation (AF) may help to develop preventive therapy. Specific heart rate (HR) patterns and autonomic changes immediately before the onset of paroxysmal AF are not fully investigated. We undertook the present study to assess HR and heart rate variability (HRV) changes before the onset of AF using 24-h Holter electrocardiographic analysis in patients without antiarrhythmic medication. Methods and Results In 27 patients, 48 episodes of AF, lasting more than 30 s and preceded by sinus rhythm for more than 1 h were analysed. The hour preceding AF was divided in 5- and 30 min blocks. HR was also analysed in the last 15 beats. In 21% of the episodes, HR decreased greater than or equal to5% in the last 5 min (defined as deceleration); it increased greater than or equal to5% in 37% (defined as acceleration). HR, standard deviation (SD) and SD corrected for RR interval changed significantly in the last 5 min in the total group. Acceleration and deceleration were already visible over 30-min blocks in both these subgroups; changes in SD were only seen in the accelerators. The number of atrial premature beats (PACs) increased before AF, most clearly in the accelerators. Spectral HRV analysis revealed no additional information. Conclusions: Changes in HR, SD, and an increased number of PACs herald AF from at least 30 min before onset, more pronounced in accelerators. Spectral HRV parameters are not useful to foresee AF onset. This has possible implications for device therapy. (C) 2003 The European Society of Cardiology. Published by Elsevier Science Ltd. All rights reserved.