Rhythm-independent feature of heart rate dynamics common to atrial fibrillation and sinus rhythm in patients with paroxysmal atrial fibrillation.

OBJECTIVES: To examine if the long-range correlation in heart rate variability is a rhythm-independent characteristic common to both atrial fibrillation (AF) and sinus rhythm (SR) periods in patients with paroxysmal atrial fibrillation (PAF). METHODS: Holter electrocardiography was analyzed during sleep in 18 patients with paroxysmal atrial fibrillation during the atrial fibrillation (PAF-AF) and sinus rhythm (PAF-SR) periods, and also in 19 healthy controls with sinus rhythm (CTR-SR). The heart rate dynamics were assessed with the power-law spectral exponent (slope) of the log-log power spectrum between 0.0001 Hz and the breakpoint frequency. RESULTS: The slope showed a significant correlation between PAF-SR and PAF-AF (r = 0.614, p < 0.01). During sinus rhythm, the slope in paroxysmal atrial fibrillation with cardiovascular disease [PAF-SR (cvd+)] was steeper than that in paroxysmal atrial fibrillation without cardiovascular disease [PAF-SR (cvd-)] (p < 0.05). Although the slope was comparable between PAF-SR (cvd-) and CTR-SR, the slope in PAF-SR (cvd+) was steeper than that in CTR-SR (p < 0.05). A similar tendency was shown during atrial fibrillation. The slope in paroxysmal atrial fibrillation with cardiovascular disease [PAF-AF (cvd+)] was steeper than that in paroxysmal atrial fibrillation without cardiovascular disease [PAF-AF (cvd-)] (p < 0.05). Although the slope was comparable between PAF-AF (cvd-) and CTR-SR, the slope in PAF-AF (cvd+) tended to be steeper than that in CTR-SR. CONCLUSIONS: The long-range correlation in heart rate variability during sleep was a rhythm-independent characteristic and so may have a similar clinical value during atrial fibrillation and sinus rhythm in patients with paroxysmal atrial fibrillation.