Hypertension is a major cause of morbidity and mortality worldwide [
Subjects were newly diagnosed but untreated hypertensive subjects recruited from the clinics of the University College Hospital, Ibadan; through community screening exercises; and from among the staff of the University College Hospital, Ibadan. Subjects with secondary hypertension, diabetes mellitus, symptomatic heart failure, and chronic kidney disease were excluded. Informed consent was obtained from each subject, and ethical approval was obtained from the joint Institutional Review Board (IRB) of the College of Medicine, University of Ibadan/University College Hospital, Ibadan, Nigeria.
Blood samples were obtained in the morning after an overnight fast. No caffeine-containing beverages, alcohol, or smoking was allowed for at least 2 h. Subjects were not on any medications prior to sample collection. Blood was collected into test tubes on ice after 30 minutes of rest in the supine position. Plasma and serum was obtained following rapid centrifugation. A 24 h collection of urine was made the preceding day in plastic containers containing HCl (80 mmol/L final concentration). Subjects notified the start and end of the collection time. The amount of urine was quantified at return of the containers. All samples were stored at −70∘C until further analyses.
High-performance (cation exchange) liquid chromatography (HPLC) was used to determine the plasma renin, plasma aldosterone. The sensitivity and specificity of the HPLC assay are 98% and 92%, respectively. Plasma and urinary sodium and potassium concentrations were measured using a flame photometric method.
Echocardiographic examination was done using a Phillip Aloka SSD 4000 (Aloka Co. Ltd., Tokyo, Japan) machine with a 2.5–5.0 MHz linear array transducer. Measurements were made as recommended by the American Society of Echocardiography [
Data from continuous variables are presented as mean (standard deviation) or as medians with interquartile ranges while categoric data are expressed as percentages. All statistical tests were two-sided and carried out to a significance level (
Tertiles of plasma aldosterone were generated and the aldosterone groups were compared with analysis of variance for continuous data, and
Eighty-two hypertensive and fifty-one controls were studied. The clinical characteristics of the subjects are shown in Table
Clinical characteristics of the subjects.
Variable | Hypertensives | Normal controls |
|
---|---|---|---|
( |
( |
||
Age (years) | 49.8 (10.96) | 47.8 (11.21) | 0.3396 |
Weight (kg) | 74.6 (13.65) | 73.3 (16.11) | 0.4098 |
Height (cm) | 167.3 (8.43) | 165.6 (8.84) | 0.2790 |
Body mass index (kg·m−2) | 26.66 (4.654) | 26.65 (5.134) | 0.9668 |
Obese (%) | 21.2 | 18.3 | 0.8116 |
Pulse (bpm) | 75.3 (12.62) | 71.47 (12.782) | 0.0567 |
Systolic blood pressure (mmHg) | 165.45 (15.452) | 127.19 (10.401) | 0.0000 |
Diastolic blood pressure (mmHg) | 95.62 (7.137) | 76.5 (7.733) | 0.0000 |
Pulse pressure (mmHg) | 69.83 (15.452) | 50.69 (8.098) | 0.0000 |
Mean arterial blood pressure (mmHg) | 118.89 (7.778) | 93.39 (7.833) | 0.0000 |
Biochemical, hormonal, and echocardiographic characteristics of the subjects.
Variable | Hypertensives | Normal controls |
|
---|---|---|---|
( |
( |
||
Plasma sodium (mmol·L−1) | 136.44 (7.874) | 139.58 (6.591) | 0.0328 |
Plasma potassium (mmol·L−1) | 4.02 (0.801) | 4.11 (0.775) | 0.5814 |
Urinary sodium (mmol·L−1) | 68.35 (41.173) | 63.33 (40.538) | 0.4968 |
Urinary potassium (mmol·L−1) | 16.06 (10.544) | 13.99 (10.782) | 0.2036 |
Urinary sodium excretion (mmol·24 hr−1) | 103.93 (63.571) | 90.77 (50.873) | 0.4522 |
Urinary potassium excretion (mmol·24 hr−1) | 24.04 (16.527) | 20.44 (14.761) | 0.1863 |
Plasma renin (ng·mL−1) | 21.03 (6.974) | 24.66 (7.592) | 0.0013 |
Plasma aldosterone (nmol·L−1) | 245.82 (59.498) | 262.46 (58.136) | 0.1162 |
ARR | 12.66 (5.112) | 11.03 (2.657) | 0.1198 |
Left atrial diameter (cm) | 3.94 (0.511) | 3.69 (0.491) | 0.0070 |
Aortic valve opening (cm) | 1.89 (0.257) | 1.86 (0.243) | 0.4785 |
LV posterior wall thickness (cm) | 1.19 (0.193) | 1.05 (0.111) | 0.0000 |
IV septal thickness (cm) | 1.11 (0.224) | 0.97 (0.125) | 0.0000 |
LV mean wall thickness (cm) | 1.15 (0.186) | 0.99 (0.085) | 0.0000 |
LV mass index (g·m−2.7) | 52.56 (14.483) | 42.02 (8.315) | 0.0000 |
Relative wall thickness | 0.5 (0.091) | 0.46 (0.071) | 0.0264 |
LV geometry | |||
Normal geometry (%) | 15.9 | 42.0 | |
Concentric remodelling (%) | 43.9 | 50.0 | 0.0000 |
Eccentric hypertrophy (%) | 12.2 | 8.0 | |
Concentric hypertrophy (%) | 28.0 | 0 |
ARR: aldosterone-to-renin ratio; LV: left ventricular; IV: interventricular.
Table
Biochemical, hormonal, and echocardiographic characteristics of the subjects according to aldosterone concentration tertiles.
Variable | Tertile 1 | Tertile 2 | Tertile 3 |
|
---|---|---|---|---|
(<231 pmol·L−1) | (231–276 pmol·L−1) | (>276 pmol·L−1) | ||
( |
|
( |
||
Plasma aldosterone (pmol·L−1) | 187.6 (28.70) | 255.5 (11.41) | 315.0 (37.63) | 0.0000 |
Plasma renin (ng·mL−1) | 19.3 (4.313) | 21.6 (5.453) | 26.2 (9.674) | 0.0032 |
ARR | 10.1 (2.242) | 12.5 (3.019) | 13.7 (6.228) | 0.0002 |
Age (yrs) | 49.3 (10.72) | 49.9 (11.53) | 48.0 (11.10) | 0.7492 |
Body mass index | 26.3 (4.971) | 27.4 (4.349) | 26.3 (5.136) | 0.5103 |
Plasma sodium (mmol·L−1) | 138.4 (7.598) | 136.3 (6.929) | 137.9 (8.173) | 0.3514 |
Plasma potassium (mmol·L−1) | 4.25 (0.747) | 3.87 (0.804) | 3.98 (0.798) | 0.0974 |
LV internal diameter (diastole) | 4.71 (0.406) | 4.76 (0.485) | 4.76 (0.489) | 0.8697 |
LV posterior wall thickness (cm) | 1.13 (0.159) | 1.13 (0.191) | 1.14 (0.187) | 0.8970 |
IV septal thickness (cm) | 1.05 (0.184) | 1.09 (0.219) | 1.02 (0.203) | 0.2265 |
Relative wall thickness | 0.48 (0.085) | 0.48 (0.092) | 0.48 (0.082) | 0.7365 |
LV mass index (g·m−2.7) | 47.1 (9.217) | 50.9 (14.59) | 47.8 (15.85) | 0.3036 |
Systolic blood pressure (mmHg) | 154.1 (21.57) | 145.8 (24.15) | 152.4 (23.40) | 0.1871 |
Diastolic blood pressure (mmHg) | 91.5 (11.86) | 85.7 (12.28) | 87.5 (10.93) | 0.0948 |
Left atrial diameter (cm) | 3.87 (0.421) | 3.78 (0.513) | 3.89 (0.604) | 0.5749 |
LV geometry | ||||
Normal geometry (%) | 22.2 | 27.9 | 27.3 | |
Concentric remodelling (%) | 55.6 | 37.2 | 45.5 | 0.5945 |
Eccentric hypertrophy (%) | 11.1 | 14.0 | 6.8 | |
Concentric hypertrophy (%) | 11.1 | 20.9 | 20.4 |
ARR: aldosterone-to-renin ratio; LV: left ventricular; IV: interventricular.
There was no univariate association between the parameters of LV structure and the plasma aldosterone and aldosterone-to-renin ratio levels (Table
Correlation coefficients between aldosterone levels, aldosterone-to-renin ratio levels, and echocardiographic parameters of left ventricular structure.
Variables | Aldosterone | ARR |
---|---|---|
Plasma aldosterone | ||
ARR | 0.4452** | |
Plasma renin | 0.3883** | −0.5879** |
LV mass index | 0.0179 | 0.0887 |
Relative wall thickness | 0.0043 | 0.0519 |
LV mean wall thickness | 0.0381 | 0.1186 |
LV Internal diameter (diastole) | 0.0118 | 0.0472 |
LV posterior wall thickness | 0.0185 | 0.1052 |
IV septal thickness | 0.0070 | 0.0992 |
ARR: aldosterone-to-renin ratio; LV: left ventricular; IV: interventricular.
In this group of black African subjects, there was no association of plasma aldosterone with LV mass. Also, no gender-specific differences in the relationship of LV mass index with plasma aldosterone were seen. Only the age of the subjects, their body mass index, and the level of their blood pressure were associated with LV mass.
Previous studies on the association between LV mass and circulating aldosterone levels in subjects with essential hypertension had yielded conflicting results. El-Gharbawy et al. [
Vasan et al. [
Our study demonstrated an association between LV mass index and body mass index. The influence of body mass index on LV mass had been noted in previous studies [
The influence of the level of the blood pressure especially systolic blood pressure [
This study also demonstrates the independent association of age with LV mass index. This supports observations from previous studies that target organ damage in hypertension increases progressively with age [
Our study is limited in that only a single measurement of aldosterone was made and might be insufficient in estimating the daily exposure to aldosterone. The determination of 24 hr urinary aldosterone is better suited for the assessment of daily aldosterone load [
In conclusion, in our group of black newly diagnosed hypertensive subjects, we did not find an independent association of LV mass index with plasma aldosterone concentration. Age and systolic blood pressure were independently associated with LV mass in our subjects. Further studies relating the 24 hr aldosterone load might be necessary to fully evaluate the association of aldosterone and measures of LV structure.
This study was supported by the University of Ibadan Senate Research Grant (SRG/COM/2006/8C) and the University of Ibadan MacArthur Multidisciplinary Research Grant (800/406/54/01/D/2008/3).