ABC | Volume 110, Nº2, February 2018

Original Article Casali et al Short & very short-term blood pressure variability Arq Bras Cardiol. 2018; 110(2):157-165 Figure 1 – Short-term BP variability (24h-ABPM). Data are shown as mean ± SD. SBP, systolic blood pressure.Analysis using 24-hour records (total) and divided into daytime and nighttime periods. Graph shows a comparison between controls (C, green bars) and diabetic-hypertensive (DH, blue bars) groups, also including circadian behaviour differences, calculated by subtracting nighttime from daytime values (Difference, last bars of each graphic). * p < 0.05 vs. C, Student’s t-test. Table reports all values, compared by Friedman repeated measures analysis of variance on rank, post hoc Student-Newman-Keuls. † p < 0.05 vs. total period; # p < 0.05 vs. daytime period. 160 140 120 100 80 60 40 20 0 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 14 12 10 8 6 4 2 0 –2 –4 –6 20 15 10 5 0 –5 MeanSBP (mmHg) Time-rateSBP (mmHg/min) Coefficientof variationSBP (%) StandarddeviationSBP (mmHg) Total(24h) Daytime Nighttime Difference Total(24h) Daytime Nighttime Difference Total(24h) Daytime Nighttime Difference Total(24h) Daytime Nighttime Difference Variable MeanSBP (mmHg) Time-rate,SBP (mmHg/min) Coefficient of variation,SBP (%) Standard deviation ofmeanSBP (mmHg) DH C Total (24h) 111.8± 6.6 0.44± 0.06 9.8± 1.7 10.9± 1.8 Daytime 116.2±6.8 † 0.48± 0.07 † 7.3± 0.9 † 8.4± 1.0 † Nighttime 101.2± 8.4 † # 0.36±0.08 † # 8.8±2.1# 8.8±1.9 † Total (24h) 132.4± 13.8 0.56±0.13 10.3± 2.8 10.0± 2.4 Daytime 135.2±15.2 † 0.59±0.16 9.5±2.3 † 12.9±3.4 † Nighttime 128.2± 13.7 † # 0.50±0.14 † # 8.3±2.3 † # 10.6± 2.3 † # * * * * * * * * * * * the coefficient of variation and mean of standard deviation of 24-hour systolic BP were positive in DH, negative in C, and different between groups. Very short-term BP variability and HR variability (FBPM) results obtained by spectral analysis are displayed in Table 2. As expected, BP was higher in DH vs. C at rest and after standing-up maneuver. Heart rate variability, LF component of HRV, and alpha index were lower in DH vs. C. The standing-up maneuver, applied to induce sympathetic activation, resulted in differences for all HR variability components, showing the expected response to this maneuver in both groups. However, BP variability did not change after the maneuver in DH subjects, and the alpha index (spontaneous baroreflex sensitivity) was lower at rest and after the maneuver in this group when compared to controls. Autonomic response to standing-up maneuver assessed by delta indices (Figure 2) had a lower response for LF/HF ratio in DH group as compared to C group. Changes in delta HRV and delta_LF/HF variability (BPV) were not different. Correlations between very short- and short-term BP variabilities are shown in Tables 3 (C group) and 4 (DH group). In C group, some correlations were found at rest, and some after the standing-up maneuver. At rest, standard deviation of 24-hour systolic BP (24h-ABPM) was positively correlated with the LF component of BP variability (FBPM) in 24-hour evaluation; the coefficient of variation (24h-ABPM) was negatively correlated with total BP variability and alpha index (FBPM) during daytime. After standing-up maneuver, time-rate (24h-ABPM) was positively correlated with the LF component of BP variability (FBPM, 24 hours, and daytime). Table 2 – Very short-term blood pressure variability and heart rate variability (FBPM) at rest and after standing-up maneuver. Variable C (n = 12) DH (n = 51) P At rest Standing up At rest Standing up Group Condition Interaction Mean BP (mmHg) 114.6 ± 23.6 112.6 ± 18.2 129.4 ± 17.7 123.8 ± 21.6 0.019 0.494 0.147 Very short-term BPV (mmHg 2 ) 21.57 ± 12.20 37.17 ± 16.12* 25.27 ± 20.08 25.23 ± 23.04 0.504 0.058 0.047 LF component of BPV (mmHg 2 ) 1.80 ± 1.13 13.84 ± 11.93 4.59 ± 6.02 9.26 ± 10.61 0.879 < 0.001 0.060 HF component of BPV (mmHg 2 ) 1.40 ± 1.57 3.73 ± 3.02* 3.44 ± 3.46# 2.25 ± 1.64* 0.538 0.323 < 0.001 Mean HR (bpm) 66.2 ± 9.3 77.8 ± 8.7* 70.8 ± 11.9 77.2 ± 13.9* 0.419 < 0.001 0.016 HRV (s 2 ) 1.47 ± 1.71 1.07 ± 0.78 0.73 ± 0.79 0.45 ± 0.42 0.005 0.010 0.658 LF component of HRV (nu) 40.77 ± 16.84 61.48 ± 16.90 31.08 ± 21.07# 40.69 ± 23.62 0.014 < 0.001 0.339 HF component of HRV (nu) 50.65 ± 14.79 30.07 ± 15.33 49.91 ± 22.35 36.19 ± 20.48 0.842 < 0.001 0.464 LF/HF index 0.99 ± 0.76 3.33 ± 3.16 1.09 ± 1.54 2.69 ± 4.13 0.902 0.001 0.744 Alpha index (ms/mmHg) 15.04 ± 9.75 6.43 ± 5.24* 8.24 ± 7.70# 4.72 ± 3.89* < 0.001 < 0.001 0.003 Data are shown as mean ± SD. HR: heart rate, HRV: heart rate variability, BP: blood pressure, BPV: BP variability, LF: low frequency component, HF: high frequency component. *p < 0.05 vs. rest condition; #p < 0.05 vs. C; FBPM: Short-Term Blood Pressure. Two-way repeated measures ANOVA. Post hoc Student-Newman-Keuls. 160