Reduced Heart Rate Variability in Patients with Chronic Obstructive Pulmonary Disease Independent of Anticholinergic or β-agonist Medications

Figures & data

Table 1.  Characteristics of the study population

	COPD	Controls	P-value
N	41	19
Age (years)	67 ± 7	68 ± 7	0.614
Gender (M:F) (% M)	28 : 13 (68)	14 : 5 (74)	0.904
Smoking (pack-years)	52 ± 26	51 ± 13	0.836
Weight (kg)	69 ± 16	75 ± 12	0.133
BMI (kg/m^2)	24.6 ± 5.3	26.8 ± 3.3	0.108
Systolic BP (mmHg)	140 ± 17	140 ± 14	0.812
Diastolic BP (mmHg)	83 ± 18	84 ± 5	0.309
FEV1 (L)	1.16 ± 0.50	2.64 ± 0.61	<0.001
FEV1 (% of predicted)	45 ± 16	102 ± 17	<0.001
FVC (L)	2.61 ± 0.83	3.80 ± 0.78	<0.001
FVC (% of predicted)	80 ± 19	115 ± 17	<0.001
FEV1/FVC	44.2 ± 11.6	69.6 ± 7.6	<0.001
TLC (L)	6.58 ± 1.39
TLC (% of predicted)	112 ± 16
RV (L)	3.47 ± 1.02
RV (% of predicted)	152 ± 42
DL,CO (ml/mmHg/Mi)	16.0 ± 5.1
DL,CO (% of predicted)	70 ± 23

Results expressed as mean ± standard deviation, unless otherwise specified.

BMI: body mass index, BP: blood pressure, FEV₁: forced expiratory volume in 1 second, FVC: forced vital capacity, TLC: total lung capacity, RV: residual volume, D_L,CO: carbon monoxide lung diffusing capacity.

Table 2.  Time and frequency domain analysis of heart rate variability in chronic obstructive pulmonary disease patients and controls

	COPD	Controls	P
N	41	19
24-hour
Minimal HR (bpm)	50 (46-58)	49 (44-54)	0.159
Mean HR (bpm)	76 (69-82)	76 (70-79)	0.423
Maximal HR (bpm)	115 (105-126)	118 (108-127)	0.501
% bradycardia (<60 bpm)	3.0 (0.5-23.0)	7.0 (0.5-21.5)	0.427
% tachycardia (>100 bpm)	0.5 (0.5-12.0)	2.0 (0.5-8.0)	0.950
Maximal RR (s)	1.38 (1.26-1.57)	1.46 (1.33-1.56)	0.341
NN (ms)	788 (732-870)	791 (754-868)	0.645
SDNN (ms)	106 (92-127)	131 (94-157)	0.067
SDANN (ms)	95 (76-117)	108 (85-155)	0.089
rMSSD (ms)	26 (21-34)	20 (16-29)	0.139
pNN50 (%)	5.9 (1.8-10.7)	2.2 (0.9-7.6)	0.212
LF (ms^2)	228 (124-384)	237 (163-394)	0.302
HF (ms^2)	110 (58-166)	56 (40-138)	0.233
LF/HF ratio	1.9 (1.5-3.4)	3.9 (3.2-5.6)	<0.001
Daytime
NN (ms)	761 (680-829)	750 (695-796)	0.922
SDNN (ms)	90 (68-108)	94 (77-121)	0.351
SDANN (ms)	76 (55-97)	76 (66-100)	0.495
rMSSD (ms)	23 (19-33)	18 (14-21)	0.044
pNN50 (%)	4.8 (1.3-9.8)	1.2 (0.7-2.9)	0.068
LF (ms^2)	200 (95-303)	196 (116-304)	0.679
HF (ms^2)	81 (38-155)	49 (28-76)	0.144
LF/HF ratio	2.6 (1.5-3.8)	3.5 (2.9-5.6)	0.003
Nighttime
NN (ms)	866 (823-1024)	931 (861-1025)	0.183
SDNN (ms)	80 (66-95)	83 (65-99)	0.824
SDANN (ms)	59 (46-76)	60 (42-68)	0.763
rMSSD (ms)	29 (24-37)	25 (20-36)	0.302
pNN50 (%)	7.6 (4.0-15.1)	5.0 (1.4-13.9)	0.378
LF (ms^2)	325 (152-520)	384 (207-771)	0.092
HF (ms^2)	144 (74-212)	108 (54-414)	0.515
LF/HF ratio	1.8 (1.1-4.3)	4.2 (2.7-6.9)	0.004

Results expressed as median and interquartile range.

HR: heart rate, bpm: beats per minute, RR: time between successive QRS complexes; NN: mean of RR intervals, SDNN: standard deviation of all the RR intervals, SDANN: standard deviation of 5-minute average RR intervals, rMSSD: square root of the mean of the squares of consecutive RR interval differences, pNN50: proportion of RR intervals >50 ms, LF: low-frequency power, HF: high-frequency power.

Table 3.  Time-domain and frequency-domain analysis of heart rate variability in chronic obstructive pulmonary disease patients using or not ß-agonist and anticholinergic medications

	ß-agonist n =27	No ß-agonist n =14	P value	Anticholinergic n =18	No anticholinergic n =23	P value
Age (years)	66 (63-71)	69 (66-70)	0.981	67 (63-72)	67 (63-70)	0.291
FEV1 (L)	1.01 (0.70-1.16)	1.35 (1.11-1.97)	0.015	0.87 (0.65-1.11)	1.26 (0.92-1.89)	0.010
LF/HF ratio
24-hour	1.7 (1.3-3.1)	2.7 (1.7-3.5)	0.284	1.7 (1.4-2.8)	2.7 (1.6-3.6)	0.189
Daytime	2.2 (1.3-3.9)	2.7 (1.8-3.6)	0.923	1.9 (1.3-3.8)	2.9 (1.8-3.8)	0.613
Nighttime	1.7 (1.0-3.4)	2.7 (1.4-5.1)	0.192	1.6 (1.0-2.5)	2.7 (1.2-4.6)	0.193

Results expressed as median and interquartile range.

No significant difference of time domain analysis between the two groups was observed (data not shown).

FEV₁: forced expiratory volume in 1 second, LF: low-frequency power, HF: high-frequency power.

Figure 1.  Low/high frequency ratio of chronic obstructive pulmonary disease patients and healthy controls for the 24-hour, daytime and nighttime recording periods. The group mean is represented by the horizontal bar. LF/HF = Low/high frequency ratio; COPD = chronic obstructive pulmonary disease. *P < 0.005.

Figure 2.  Correlation between the 24-hour low/high frequency ratio and lung function in chronic pulmonary obstructive disease patients and controls. Significant correlations between the 24-hour low/high frequency ratio (LF/HF) and the forced expiratory volume in 1 second (FEV₁) were observed for chronic obstructive pulmonary disease (COPD) patients (r = 0.342; P = 0.028) as well as the overall study population (r = 0.499; P < 0.001), whereas no correlation was documented for the controls (r = 0.206; P = 0.397). L = liters.