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Table 2 Time-domain indexes of heart rate variability before and at various intervals after coronary artery bypass grafting

From: Coronary artery bypass surgery and longitudinal evaluation of the autonomic cardiovascular function

Variable Group Preoperative After surgery
    3 days 6 days 15 days 30 days 60 days 90 days
Mean R–R (ms) CABG 903 ± 40 761 ± 45* 781 ± 42* 790 ± 36* 802 ± 26* 801 ± 36 802 ± 35
  CAD 856 ± 49 - - - 842 ± 38 816 ± 33 835 ± 47
  Healthy 860 ± 36 - - - - - -
SDNN (ms) CABG 35 ± 3 16 ± 2* 16 ± 2* 19 ± 2* 25 ± 2* 32 ± 3 27 ± 3
  CAD 31 ± 4 - - - 29 ± 3 30 ± 3 31 ± 2
  Healthy 42 ± 5 - - - - - -
SDANN (ms) CABG 16 ± 3 6 ± 1* 6 ± 1* 9 ± 1* 15 ± 3 18 ± 3 14 ± 2
  CAD 21 ± 4 - - - 19 ± 3 20 ± 3 20 ± 3
  Healthy 39 ± 7 - - - - - -
RMSSD (ms) CABG 24 ± 4 10 ± 2* 10 ± 1* 12 ± 1* 19 ± 4 21 ± 3 19 ± 2
  CAD 22 ± 3 - - - 18 ± 3 19 ± 2 20 ± 4
  Healthy 27 ± 3 - - - - - -
pNN50 (%) CABG 8 ± 0 3 ± 0* 3 ± 0* 3 ± 0* 4 ± 0* 7 ± 0 6 ± 0
  CAD 4 ± 0 - - - 3 ± 0 4 ± 0 3 ± 0
  Healthy 11 ± 0b - - - - - -
  1. Values are means ± SEM. *P < 0.05 versus CABG preoperative value; P < 0.05 versus CABG and CAD. CABG, patients who underwent coronary artery bypass grafting; CAD, patients with coronary artery disease who did not undergo surgery; healthy, control subjects without CAD; pNN50, percentage number of pairs of adjacent R–R intervals differing by more than 50 ms; RMSSD, square root of the mean of squares of differences between adjacent R–R intervals; SDANN, standard deviation of the averages of the R–R intervals calculated in 5-minute segments; SDNN, standard deviation of all R–R intervals.