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Figure 1 Continuous 5-min data of time-domain parameters of heart rate variability (HRV) during the 2 h preceding the onset of atrial fibrillation/flutter (AF) (filled circles) or in the corresponding study window in controls (unfilled circles). A = RR interval; B = SD; C = rMSSD; D = pNN50. See text for abbreviations. P values in the figures represent the group by time interaction results.