Resting heart rate predicts cardiac autonomic modulation during passive head-up tilt in subjects without cardiovascular diseases

Figures & data

Table 1. Study population demographics, laboratory and supine hemodynamic values in the heart rate tertiles calculated according to sexes.

	HR tertile 1	HR tertile 2	HR tertile 3	All
Number (male/female)	187 (93/94)	190 (98/92)	192 (96/96)	569 (287/282)
Age (years)	44.2 (42.4, 46.0)	45.6 (44.0, 47.2)	44.9 (43.3, 46.5)	44.9 (43.9, 45.9)
Smoking
Never	99 (53%)	113 (59%)	119 (62%)	331 (58%)
Previous	59 (32%)	57 (30%)	49 (26%)	165 (29%)
Present	28 (15%)	20 (11%)	24 (13%)	72 (13%)
Smoking (pack years)	4.3 (2.3, 6.3)	4.6 (2.6, 6.7)	7.7 (5.1, 10.3)	5.6 (4.3, 6.9)
Physical exercise (times per week)	3.3 (3.0, 3.6)	3.0 (2.7, 3.2)	3.1 (2.9, 3.3)	3.1 (3.0, 3.2)
Alcohol (doses per week)	4.2 (3.3, 5.1)	4.2 (3.5, 5.0)	4.9 (4.0, 5.7)	4.4 (4.0, 4.9)
Body mass index (kg/m^2)	26.0 (25.5, 26.6)	26.6 (26.0, 27.2)	27.6* (26.9, 28.3)	26.7 (26.4, 27.1)
Hematocrit	0.42 (0.42, 0.42)	0.42 (0.42, 0.42)	0.42 (0.41, 0.43)	0.42 (0.42, 0.42)
C reactive protein (mg/l)	1.1 (1.1, 1.4)	1.7 (1.2, 2.0)	2.2* (1.6, 2.7)	1.7 (1.4, 1.9)
eGFR (ml/min/1.73m^2)	99 (97, 101)	99 (96, 101)	98 (96, 100)	99 (97, 100)
Fasting plasma
Glucose (mmol/l)	5.4 (5.3, 5.4)	5.4 (5.3, 5.5)	5.5* (5.4, 5.6)	5.4 (5.4, 5.5)
Total cholesterol (mmol/l)	5.1 (5.0, 5.2)	5.1 (5.0, 5.3)	5.2 (5.0, 5.3)	5.2 (5.1, 5.2)
Triglycerides (mmol/l)	1.1 (1.0, 1.2)	1.2* (1.1, 1.3)	1.5^*† (1.3, 1.7)	1.3 (1.2, 1.3)
HDL cholesterol (mmol/l)	1.7 (1.7, 1.8)	1.6* (1.5, 1.6)	1.5* (1.4, 1.5)	1.6 (1.5, 1.6)
LDL cholesterol (mmol/l)	3.0 (2.8, 3.0)	3.0 (3.0, 3.2)	3.1 (2.9, 3.2)	3.0 (3.0, 3.1)
Heart rate (1/min)	54 (53, 55)	62* (62, 63)	74^*† (73, 75)	64 (63, 64)
Systolic blood pressure (mmHg)	131 (128, 134)	135 (132, 137)	141^*† (138, 144)	136 (134, 137)
Diastolic blood pressure (mmHg)	75 (73, 77)	80* (78, 82)	83^*† (81, 85)	79 (78, 81)
Pulse wave velocity (m/s)	7.9 (7.6, 8.1)	8.6* (8.3, 8.9)	8.9* (8.6, 9.2)	8.5 (8.3, 8.6)

eGFR: estimated glomerular filtration rate by CKD-EPI cystatin C and creatinine equation; HDL: high-density lipoprotein; LDL: low-density lipoprotein.

Values are means (confidence intervals) or numbers. Hemodynamic variables are means of 3 min continuous supine measures. Statistics: *p < .05 vs. tertile 1, ^†p < .05 vs. tertile 2; analysis of variance, Tukey HSD/Tamhane’s T2 correction in post-hoc testing. Natural logarithms of C reactive protein and fasting triglyceride concentrations were used in statistical analyses to normalize their distributions.

Figure 1. Mean (95% confidence intervals) supine and upright heart rate (A), RR-interval (B), and the change in heart rate (C), and RR-interval (D) during passive head-up tilt according to the mean supine heart rate (HR) tertiles; *p < .001, ^†p < .05 statistically significant differences in the analysis of variance with Tukey’s HSD correction in post-hoc testing.

Figure 2. Mean (95% confidence intervals) supine and upright standard deviation of normal-to-normal RR-intervals (SDNN) (A), and the square root of mean squared differences of normal-to-normal RR-intervals (RMSSD) (B) according to the mean supine heart rate (HR) tertiles. Values are presented as natural logarithms (Ln) of the variables to normalize their distributions; *p < .001, ^†p < .05 statistically significant differences in the analysis of variance with Tukey’s HSD post-hoc test.

Figure 3. Mean (95% confidence intervals) supine and upright total power (A), low-frequency power (B), high-frequency power (C), and low to high-frequency power ratio (D) according to the mean supine heart rate (HR) tertiles. Values are presented as natural logarithms (Ln) of the variables to normalize their distributions; *p < .001, statistically significant differences in the analysis of variance with Tukey’s HSD post-hoc test.

Table 2. Actual heart rate variability values according to resting heart rate tertiles during 3 min measurement at supine and upright position.

	Heart rate tertile 1	Heart rate tertile 2	Heart rate tertile 3	All
	n = 187	n = 190	n = 192	n = 569
Supine
Mean RR-interval (ms)	1120 (1105, 1134)	967* (960, 974)	821^*† (810, 831)	968 (952, 983)
SDNN (ms)	36 (27, 49)	32* (24, 45)	25^*† (17, 34)	31 (22, 43)
RMSSD (ms)	41 (29, 59)	32* (24, 45)	21^*† (15, 31)	36 (21, 45)
Power in low frequency range (ms^2)	444 (193, 972)	434 (200, 877)	252^*† (118, 458)	354 (165, 758)
Power in high frequency range (ms^2)	526 (274, 1088)	331* (163, 692)	160^*† (68, 423)	331 (133, 688)
Low- to high-frequency ratio	0.86 (0.44, 1.66)	1.24* (0.61, 2.28)	1.53^*† (0.73, 3.03)	1.16 (0.60, 2.31)
Total power (ms^2)	1149 (589, 2082)	849 (447, 1748)	495^*† (230, 952)	782 (397, 1554)
Upright
Mean RR-interval (ms)	901 (885, 917)	804* (794, 814)	708^*† (697, 718)	803 (793, 813)
SDNN (ms)	28 (20, 40)	23* (16, 33)	19^*† (13, 26)	23 (16, 33)
RMSSD (ms)	21 (15, 31)	17* (13, 22)	12^*† (9, 19)	17 (11, 24)
Power in low frequency range (ms^2)	436 (156, 916)	250* (107, 598)	195^*† (85, 383)	260 (112, 639)
Power in high frequency range (ms^2)	137 (71, 304)	83* (36, 179)	54^*† (36, 179)	88 (36, 200)
Low- to high-frequency ratio	2.70 (1.15, 6.21)	3.51 (1.37, 7.03)	3.49 (1.84, 6.52)	3.22 (1.42, 6.72)
Total power (ms^2)	777 (323, 1330)	424* (208, 931)	291^*† (134, 645)	426 (206, 983)

SDNN: standard deviation of all normal RR intervals; RMSSD: the root mean square of differences between adjacent normal RR intervals.

Values are medians (interquartile range). *p < .05 vs. tertile 1, ^†p < .05 vs. tertile 2; analysis of variance, Tukey HSD/Tamhane’s T2 correction in post-hoc testing; natural logarithms are used normalizing distributions for statistical analysis.

Figure 4. Mean (95% confidence intervals) supine and upright total power (A), low-frequency power (B), high-frequency power (C), and low to high-frequency power ratio (D) according to the mean supine heart rate (HR) tertiles. The dependence of heart rate on heart rate variability was weakened by dividing heart rate variability parameters by average RR-intervals to the fourth power [17]. Values are presented as natural logarithms (Ln) of the variables to normalize their distributions; *p < .001, ^†p < .05 statistically significant differences in the analysis of variance with Tukey’s HSD post-hoc test.

Sacha J, Sobon J, Sacha K, et al. Heart rate impact on the reproducibility of heart rate variability analysis. Int J Cardiol. 2013;168(4):4257–4259.

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Data availability statement

The data been used during the present study is not publicly available as our clinical database contains several indirect identifiers and the informed consent obtained does not allow publication of individual patient data. However, the datasets are available from the corresponding author on reasonable request.