Heart rate variability on antihypertensive drugs in black patients living in sub-Saharan Africa

Figures & data

Figure 1. Flow diagram of patients. Logistical reasons included delayed replenishment of the local supply of study medications and internet or computer failures at local centres. HCTZ, hydrochlorothiazide. HRV refers to patients, who had at least one measurement of heart rate variability after randomization. Cohort refers to patients with all scheduled visits available for analysis.

Table I. Baseline characteristics by type of analysis and randomization group.

Characteristic Randomization	Type of analysis
	All patients		Cohort
	Old	New	Old	New
Number (%) with characteristic
All patients in category	72	84	39	47
Women	37 (51)	46 (55)	24 (62)	24 (51)
Smokers	5 (7)	1 (1)	1 (3)	0 (0)
Drinking alcohol	22 (31)	25 (30)	11 (28)	18 (38)
Treatment naïve	49 (68)	56 (67)	26 (67)	28 (60)
Mean± SD of characteristic
Age, years	51.7 ± 8.2	51.4 ± 9.5	52.7 ± 7.6	50.9 ± 9.1
Body mass index (kg/m^2)	28.7 ± 4.7	27.6 ± 4.9	28.9 ± 4.9	27.5 ± 4.4
Waist circumference (cm)	95.2 ± 11.5	93.4 ± 11.3	97.6 ± 11.2	92.8 ± 10.4
Sitting measurements of
Systolic pressure (mmHg)	155.9 ± 10.4	156.5 ± 12.5	157.3 ± 11.1	153.2 ± 11.1
Diastolic pressure (mmHg)	92.6 ± 9.8	92.1 ± 10.5	95.4 ± 9.4	90.6 ± 8.5
Heart rate (beats/min)	70.4 ± 10.8	70.4 ± 9.4	71.8 ± 9.1	71.0 ± 10.6
Heart rate variability measurements
Total power (log ms^2)	4.29 ± 0.35	4.28 ± 0.38	4.32 ± 0.34	4.25 ± 0.34
(geometric mean)	(19,561)	(19,116)	(21,111)	(17,824)
Low-frequency power (nu)	41.8 ± 19.8	45.2 ± 16.5	41.9 ± 20.9	48.6 ± 15.6
High-frequency power (nu)	18.8 ± 14.3	21.1 ± 14.5	20.0 ± 16.2	19.6 ± 13.6
Low- to high-frequency ratio, log	0.41 ± 0.37	0.39 ± 0.35	0.41 ± 0.42	0.46 ± 0.33
(geometric mean)	(2.59)	(2.45)	(2.56)	(2.88)

The overall analysis encompasses patients with at least one measurement of heart rate variability after randomization and the cohort analysis patients with all scheduled visits available for analysis. Old and new refer to single-pill combinations of hydrochlorothiazide plus bisoprolol and valsartan plus amlodipine. Measurements of blood pressure are averages of three consecutive readings in the sitting position. Heart rate variability was analysed using fast Fourier transform. Between-group differences in the baseline characteristics among all patients (p ≥ 0.06) and among those in the cohort analysis (p ≥ 0.09) were not significant with the exception of waist circumference (p = 0.04) and diastolic blood pressure (p = 0.015) in the cohort analysis.

Figure 2. Total power (A), low-frequency power (B), high-frequency power (C) and low- to high-frequency ratio (D) at randomization and during follow-up in patients randomized to old drugs (n = 72) or new drugs (n = 84). Heart rate variability was analysed using fast Fourier transform. Plotted values are means± SE. The number of patients contributing to the means is given. p values denote the significance of the between-group differences derived from a mixed model. Significance of the between-group differences at individual visits: *p ≤ 0.05; ^†p ≤ 0.01; ^‡p ≤ 0.001.

Table II. Changes in heart rate and heart rate variability by randomization group.

Characteristic	Old	New	Δ (CI)	p
Number	72	84
Heart rate measurements
Heart rate (beats/min)	− 9.5 ± 1.6^‡	− 2.2 ± 1.4	7.3 (5.6 to 9.4)	< 0.0001
Total power (log ms^2)	− 0.20 ± 0.06^‡	− 0.06 ± 0.05	0.13 (0.04 to 0.22)	0.0038
(percent)	− 4.7	− 1.29	3.4 (1.0 to 5.7)
Low-frequency power (nu)	− 1.0 ± 2.7	− 0.4 ± 2.2	3.6 (− 0.08 to 7.4)	0.057
High-frequency power (nu)	7.1 ± 2.3^†	2.4 ± 2.0	− 3.3 (− 6.6 to − 0.02)	0.050
Low- to high-frequency ratio	− 0.15 ± 0.05^†	− 0.06 ± 0.05	0.08 (0.01 to 0.15)	0.040
(percent)	− 36.6	− 15.4	21.2 (2.7 to 39.8)

The overall analysis encompasses patients with at least one measurement of heart rate variability after randomization. Heart rate variability was analysed using fast Fourier transform. Within-group changes (follow-up minus baseline) are mean± SE. Δ (CI) refers to the baseline-adjusted differences 95% confidence interval) of the treatment effects (new minus old). p-values were computed using a mixed model. Significance of the within-group changes: *p ≤ 0.05; ^†p ≤ 0.01; ^‡p ≤ 0.001.