Abstract
The authors conducted a subanalysis of the ReHOT (Resistant Hypertension Optimal Treatment) study to evaluate the association between endothelial dysfunction and resistant hypertension in a population of patients treated in a staged fashion for hypertension. One hundred and three hypertensive patients were followed for 6 months and participated in seven visits (V0‐V6) 28 days apart. There was a first phase (V0‐V3) of antihypertensive adjustment with three drugs and determination of resistant hypertension and a second randomized phase (V3‐V6) of treatment with a fourth drug (clonidine or spironolactone) in the hypertensive patients characterized as resistant. Of the 103 patients included, 86 (83.5%) underwent the randomization visit (V3), 71 were characterized as non‐resistant hypertensives (82.5%), and 15 as resistant hypertensives (17.5%). Serum asymmetric dimethylarginine (ADMA) was shown to be an independent predictor of resistant hypertension after adjustment for multiple variables (OR: 11.42, 95% CI: 1.02‐127.71, P = .048), and in addition, there was a reduction in blood pressure levels and ADMA values during follow‐up with a positive correlation in both groups and a greater reduction in the group of resistant hypertensives. We demonstrated that ADMA was an independent predictor of resistant hypertension, and we observed that the improvement in blood pressure levels obtained with the treatment was proportional to the reduction in ADMA values, suggesting a complementary role of ADMA not only as a stratification tool for the occurrence of resistant hypertension, but also as a possible therapeutic target in this population.
Keywords: endothelial dysfunction, hypertension, resistance
1. INTRODUCTION
The prevalence of resistant hypertension in the general population is around 8.9%‐11.7%, 1 , 2 , 3 and factors related to its development include obesity, advanced age, obstructive sleep apnea, left ventricular hypertrophy, excessive consumption of salt and alcohol, black race, diabetes mellitus (DM), female sex, chronic kidney disease (CKD), and high blood pressure (BP) in the first evaluation. 4 , 5 , 6 , 7 , 8 The multicenter study ReHOT (Resistant Hypertension Optimal Treatment), which evaluated 1597 individuals between 2010 and 2014, showed a prevalence of resistant hypertension of 11.7% and demonstrated that DM, previous history of cerebrovascular accident (CVA) and BP ≥ 180/110 mm Hg at the beginning of follow‐up were independent predictor of its occurrence. 3 Resistant hypertensive patients have a worse cardiovascular prognosis compared to other hypertensive groups, and Daugherty et al 9 determined risk of death, acute coronary syndrome, CVA, CKD, and heart failure to be 1.47 times higher in this population.
The main mechanism by which hypertension promotes target organ damage is insidious and progressive aggression to the vessel wall throughout the vascular system, especially chronic endothelial damage. 10 Efforts have been made to quantify the degree of endothelial dysfunction in different populations, and among the non‐invasive methods used, ADMA analysis 11 , 12 stands out. ADMA is a potent competitive inhibitor of nitric oxide synthase (NOS), an enzyme responsible for the synthesis of nitric oxide (NO) through the conversion of L‐arginine to L‐citrulline, 13 and it is formed by the activity of protein arginine N‐methyltransferases, which act by methylating arginine residues in proteins or polypeptides. 14 ADMA is mainly metabolized by an enzyme called dimethylarginine dimethylaminohydrolase (DDAH), which has two isoforms 15 and is attenuated by factors such as the presence of oxidized LDL, inflammatory cytokines, hyperhomocysteinemia, hyperglycemia, infectious agents, and high doses of erythropoietin. 15 , 16 , 17
Reduction in endothelium‐derived NO and increase in serum ADMA levels are associated with changes in adipocyte function and oxidative stress pathways, increased inflammatory response and activation of the renin‐angiotensin‐aldosterone system (RAAS) and the autonomic nervous system, constituting an interconnected endothelial‐neuroendocrine regulatory network that promotes hypertension. Thus, high concentrations of serum ADMA stimulate the production of tumor necrosis factor alpha (TNF‐alpha) and mediators, including C‐reactive protein (CRP), via ROS/NF‐KB. 18 In addition, they provide increased oxidative stress and activation of RAAS. In addition, they provide increased oxidative stress and activation of RAAS, since angiotensin II activates NADPH oxidase to generate ROS (reactive oxygen species). 19 The addition of reactive oxygen species, systemic inflammation, and reduction of NO bioavailability, in turn, are promoters of the activation of the sympathetic autonomic nervous system by several mechanisms, including modulation of neurotransmitter release, inhibition of receptors, and changes in intracellular signaling pathways. 20
In the scenario of resistant hypertension, the Brazilian multicenter study called ReHOT (Resistant Hypertension Optimal Treatment) 3 was developed with the aim of evaluating individuals with hypertension to identify resistant hypertension and standardize therapeutic regimens, with a focus on the randomization of two anti‐hypertensive drugs as the 4th preferred class (spironolactone and clonidine). It was found that 11.7% of the 1597 patients recruited were resistant hypertensive and that spironolactone produced a greater decrease in 24‐hour systolic and diastolic BP and diastolic daytime ambulatory BP over 6 months follow‐up, in relation to clonidine. The current study used a subpopulation of ReHOT to analyze the association between endothelial dysfunction measured by ADMA and resistant hypertension.
2. MATERIALS AND METHODS
This was a pre‐specified randomized intervention study involving a subpopulation of individuals from the ReHOT study 3 seen at the Center of Hypertension and Cardiovascular Metabolism of UNIFESP/EPM and evaluated endothelial function through ADMA in treated hypertensive patients.
The inclusion criteria were age between 18 and 75 years, systolic BP ≥ 160 and ≤220 mm Hg and/or diastolic BP ≥ 100 mm Hg at visit 0. At the same time, systolic BP exclusion > 220 mm Hg at visit 0, presence of cardiovascular events in the last 6 months, CKD stages IV and V (glomerular filtration rate < 30 mL/min), left ventricular systolic heart failure (functional class III and IV), history of malignant disease with life expectancy < 2 years, alcoholism, psychiatric illnesses that compromise follow‐up of the study, women of childbearing age not using effective contraception, pregnancy, severe arrhythmias, valvulopathies, 2nd and 3rd degree atrioventricular block with no pacemaker, severe liver disease, hypersensitivity to study drugs, grade III/IV retinopathy, and patients with compulsory use of beta‐blockers.
One hundred and three hypertensive patients were selected between October 2010 and February 2014, and they participated in two study phases, which totaled seven visits with a 28‐day interval between them (±5 days).
2.1. First phase
All included hypertensive individuals underwent four initial monthly visits (V0‐V3) and were submitted to adjustments of antihypertensive treatment, according to protocol. At visit 0, patients with systolic BP greater than or equal to 160 mm Hg and less or equal to 220 mm Hg and/or diastolic BP greater than or equal to 100 mm Hg signed an informed consent form, underwent clinical evaluation, pharmaceutical care, physical examination and started antihypertensive treatment with a combination of chlorthalidone 25 mg once daily and enalapril 20 mg twice daily (replaced by losartan 50 mg twice daily in those with ACEI intolerance). At V1, patients underwent clinical evaluation and pharmaceutical care, physical examination with BP measurement, blood drawing for routine laboratory tests (see below) and serum ADMA, electrocardiogram, and 24‐hour ABPM (ambulatory blood pressure monitoring). If BP remained above 140/90 mm Hg, amlodipine 5 mg once daily was added to the antihypertensive regimen. At V2, the patients were submitted to clinical evaluation and pharmaceutical care, in addition to physical examination with BP measurement. If BP remained above 140/90 mm Hg, amlodipine was increased to 5 mg twice daily. At V3, patients underwent clinical evaluation and pharmaceutical care, physical examination with BP measurement, blood drawing for routine laboratory tests (see below) and serum ADMA, electrocardiogram, and 24‐hour ABPM. Those who maintained BP at the clinic equal to or greater than 140/90 mm Hg and mean 24‐hour blood pressure on ABPM equal to or greater than 130/80 mm Hg were considered resistant hypertensive patients and proceeded to the randomized treatment phase. Those with adequate blood pressure control in V3 underwent three further follow‐up visits (V4‐6).
2.2. Second phase (randomized treatment)
Individuals with inadequate BP control (BP ≥ 140/90 mm Hg at clinic visit and/or overall mean blood pressure at ABPM ≥ 130/80 mm Hg) at V3 were characterized as resistant hypertensive patients and were randomized to receive clonidine (0.1 mg twice daily) or spironolactone (12.5 mg once daily) with dose adjustment during V4‐V6 visits. At V4 and V5, the resistant hypertensives were submitted to clinical evaluation and pharmaceutical care, in addition to a physical examination with BP measurement. If BP remained above 140/90 mm Hg, clonidine was increased to 0.2 mg twice daily at V4 and 0.3 mg twice daily at V5, and spironolactone was increased to 25 mg once daily at V4 and 50 mg once daily at V5. Non‐resistant patients underwent two visits for pharmaceutical care every 4 weeks. At V6, all patients (resistant and non‐resistant hypertensives) underwent clinical evaluation and pharmaceutical care, physical examination with BP measurement, blood drawing for routine laboratory tests (see below) and serum ADMA, electrocardiogram, and 24‐hour ABPM. There was no adjustment of antihypertensives at this visit.
Laboratory tests included complete blood count, blood fasting glucose, serum sodium, potassium, creatinine, urea, total cholesterol and fractions, triglycerides, uric acid, ADMA, and urinalysis. ADMA values were determined by high‐performance liquid chromatography (HPLC) with fluorescence detector (Shimadzu ClassVP) as described by Teerlinket et al, 21 and the serum samples were immediately stored in −80°C.
Individuals with a glomerular filtration rate less than 60 mL/min were considered having CKD, determined by the Chronic Kidney Disease Epidemiology Collaboration (CKD‐EPI) equation. 22 In addition, cardiovascular disease (CVD) is defined as the set of comorbidities that include coronary artery disease, cerebrovascular disease, peripheral obstructive arterial disease, and heart failure. 23
Pharmaceutical care was performed at all study visits for strict control of adherence to the pharmacological treatment instituted. Medication adherence was monitored by pill count (all medications were provided to patients, and there was a log form in the case report form of the study to control and calculate drug compliance). We considered to be adherent those patients taking all medications correctly > 80% of the time on all days. 24
The study protocol was approved by the responsible ethics committee (research ethics committee of Federal University of São Paulo), and an informed consent form was signed by each participating patient (CEP 1779/09).
Statistical analysis was performed with SPSS 23 software from IBM. Categorical variables (qualitative), nominal and ordinal, were described with absolute value and percentage, parametric quantitative variables with mean and standard deviation, and non‐parametric quantitative variables with median and interquartile range. Comparisons between unrelated qualitative variables were performed using the Pearson chi‐square test or Fisher exact test. Comparisons between related qualitative variables involving more than two groups were performed by the Cochran test. The comparisons between unrelated parametric quantitative variables involving two groups were performed by the independent t test, while the non‐parametric ones were performed by the Mann‐Whitney test. Comparisons between unrelated parametric quantitative variables involving more than two groups were performed by one‐way ANOVA for independent samples, while non‐parametric ones were evaluated by the Kruskal‐Wallis test. The comparisons between related parametric quantitative variables involving more than two groups were performed by one‐way ANOVA with repeated measures, while non‐parametric ones were evaluated by the Friedman test. Comparisons between related quantitative variables involving more than two groups and a dichotomous categorical variable were performed by mixed ANOVA. The correlation between non‐parametric quantitative variables was performed by the Spearman bivariate correlation test. The determination of the relationship of the dependent variable resistant hypertension with the independent variables serum ADMA, sex, initial systolic BP, initial diastolic BP, type 2 DM, dyslipidemia, HDL cholesterol, metabolic syndrome, CKD, proteinuria, cerebrovascular disease, and number of pre‐study antihypertensive medications was performed by binary logistic regression. The Kolmogorov‐Smirnov test was used to evaluate the normality of the data. Statistical significance was defined as P < 0.05.
3. RESULTS
One hundred and three patients were sequentially enrolled in the study and initiated follow‐up (V0). Of these, 86 (83.5%) underwent the randomization at visit (V3) and 83 (80.6%) completed the study protocol. Seventy‐one participants of the 86 patients who underwent V3 were characterized as non‐resistant hypertensive patients (82.5%) and 15 as resistant hypertensives (17.5%). At the initial visit (V0), of the 86 individuals who underwent the third visit (V3), 42 used at least three classes of antihypertensives including a diuretic (48.8%) and had a BP higher than 140/90 mm Hg (inclusion criterion), which demonstrated a considerable rate of pseudoresistance, possibly due to poor adherence.
The demographic characteristics at the beginning of the follow‐up of the population of resistant and non‐resistant hypertensives are described in Table 1 and demonstrate higher diastolic BP levels at the initial visit and higher mean systolic and diastolic BP at visit 1, besides the use of more pre‐study classes of antihypertensive drugs in the resistant hypertension group. In addition, there was a higher prevalence of males, cerebrovascular disease, CKD, low HDL, and proteinuria, as well as higher serum ADMA levels and lower total cholesterol values in the same group.
TABLE 1.
Demographic characteristics of the population—resistant and non‐resistant hypertensives
| Resistant hypertensives (15) | Non‐resistant hypertensives (71) | P value | |
|---|---|---|---|
| Age—y (SD) | 53.9 (11.3) | 54.7 (10.4) | 0.78 |
| Male sex—n (%) | 9 (60.0) | 23 (32.4) | 0.04 |
| Black race—n (%) | 3 (20.0) | 17 (23.9) | 0.52 |
| Weight—kg (IQR) | 91.8 (29.7) | 75.5 (24.6) | 0.14 |
| Body mass index—kg/m2 (SD) | 32.1 (5.2) | 31.2 (6.2) | 0.60 |
| Waist circumference—cm (SD) | 104.8 (13.6) | 101.2 (15.9) | 0.42 |
| Systolic arterial blood pressure—mm Hg (IQR) | 167 (30) | 167 (14) | 0.16 |
| Diastolic arterial blood pressure—mm Hg (IQR) | 112 (27) | 101 (10) | 0.03 |
| Mean systolic blood pressure, ABPM—mm Hg (IQR) | 162 (34) | 127 (16) | <0.001 |
| Mean diastolic blood pressure, ABPM—mm Hg (IQR) | 99 (23) | 78 (12) | <0.001 |
| Type 2 diabetes mellitus—n (%) | 6 (40.0) | 22 (31.0) | 0.55 |
| Time of hypertension—y (IQR) | 16.0 (25.0) | 16.0 (19.0) | 0.67 |
| Number of pre‐study antihypertensive drugs (IQR) | 5.0 (1.0) | 2.0 (2.0) | <0.001 |
| Dyslipidemia—n (%) | 15 (100.0) | 59 (83.1) | 0.11 |
| ‐ Hypercholesterolemia | 8 (53.3) | 38 (53.3) | 0.99 |
| ‐ Low HDL | 15 (100.0) | 47 (66.2) | 0.01 |
| ‐ Hypertriglyceridemia | 8 (53.3) | 28 (39.4) | 0.32 |
| Obesity—n (%) | 9 (60.0) | 37 (52.1) | 0.95 |
| Metabolic syndrome—n (%) | 13 (86.7) | 55 (77.5) | 0.72 |
| Cardiovascular disease—n (%) | 4 (26.7) | 7 (9.9) | 0.08 |
| ‐ Coronary arterial disease—n (%) | 0 (0.0) | 3 (4.2) | 1.00 |
| ‐ Previous CVA or TIA—n (%) | 4 (26.7) | 3 (4.2) | 0.02 |
| ‐ Chronic peripheral arterial disease—n (%) | 0 (0.0) | 2 (2.8) | 1.00 |
| ‐ Heart failure—n (%) | 0 (0.0) | 0 (0.0) | = |
| Chronic kidney disease (GFR < 60 mL/min)—n (%) | 5 (33.3) | 7 (9.9) | 0.03 |
| Proteinuria—n (%) | 7 (46.7) | 12 (16.9) | 0.02 |
| Family history of CVD—n (%) | 8 (57.1) | 42 (60.9) | 0.79 |
| Smoking—n (%) | 5 (33.3) | 31 (43.7) | 0.46 |
| Fasting glucose—mg/dL (IQR) | 86 (37) | 95 (27) | 0.19 |
| Total cholesterol—mg/dL (SD) | 165 (44) | 186 (32) | 0.03 |
| HDL—mg/dL (IQR) | 35 (6) | 41 (17) | 0.01 |
| LDL—mg/dL (IQR) | 97 (47) | 108 (30) | 0.06 |
| Triglycerides—mg/dL (IQR) | 158 (114) | 130 (77) | 0.45 |
| Creatinine—mg/dL (IQR) | 1.1 (0.5) | 0.9 (0.3) | 0.01 |
| GFR—mL/min (SD) | 71.9 (24.7) | 82.3 (18.4) | 0.07 |
| ADMA—µmol/L (IQR) | 0.89 (0.34) | 0.55 (0.19) | <0.001 |
Abbreviations: ABPM, ambulatory blood pressure monitoring; ADMA, asymmetric dimethylarginine; CVA, cerebral vascular accident; CVD, cardiovascular disease; GFR, glomerular filtration rate; IQR, interquartile range; SD, standard deviation; TIA, transient ischemic accident.
Table 2 describes the characteristics of the population according to serum ADMA tertiles at visit 1 and showed higher values of systolic BP at the initial visit and higher mean systolic and diastolic BP at visit 1, besides the use of a greater number of pre‐study classes of antihypertensive drugs in the third tertile group of serum ADMA. There was also a higher prevalence of hypercholesterolemia and CVD in the same group.
TABLE 2.
Demographic characteristics of the population—serum ADMA tertiles
| ADMA ≤ 0.51 (33) a | ADMA 0.52 to 0.67 (31) a | ADMA ≥ 0.68 (32) a | P value | |
|---|---|---|---|---|
| Age—y (SD) | 52.5 (11.9) | 52.3 (12.0) | 56.5 (9.8) | 0.26 |
| Male sex—n (%) | 14 (42.4) | 10 (32.3) | 11 (34.4) | 0.67 |
| Black race—n (%) | 8 (24.2) | 7 (22.6) | 7 (21.9) | 0.97 |
| Weight—kg (IQR) | 74.2 (24.5) | 81.0 (40.0) | 77.8 (27.4) | 0.62 |
| Body mass index—kg/m2 (SD) | 30.9 (5.5) | 32.6 (7.1) | 30.3 (4.8) | 0.29 |
| Waist circumference—cm (SD) | 99.1 (13.8) | 105.1 (17.7) | 100.1 (12.9) | 0.23 |
| Systolic arterial blood pressure—mm Hg (IQR) | 162 (20) | 168 (20) | 169 (19) | <0.001 |
| Diastolic arterial blood pressure—mm Hg (IQR) | 102 (7) | 104 (18) | 99 (21) | 0.39 |
| Mean systolic blood pressure, ABPM—mm Hg (IQR) | 120 (9) | 133 (21) | 151 (29) | <0.001 |
| Mean diastolic blood pressure, ABPM—mm Hg (IQR) | 75 (12) | 83 (12) | 89 (24) | <0.001 |
| Type 2 diabetes mellitus—n (%) | 9 (27.3) | 7 (22.6) | 12 (37.5) | 0.41 |
| Time of hypertension—y (IQR) | 13.0 (18.5) | 12.0 (18.0) | 20.0 (22.7) | 0.09 |
| Number of pre‐study antihypertensive drugs (IQR) | 2.0 (2.0) | 3.0 (2.0) | 4.0 (2.0) | <0.001 |
| Dyslipidemia—n (%) | 28 (84.8) | 25 (80.6) | 29 (90.6) | 0.55 |
| ‐ Hypercholesterolemia | 13 (39.4) | 14 (45.2) | 22 (68.8) | 0.04 |
| ‐ Low HDL | 25 (75.8) | 21 (67.7) | 23 (71.9) | 0.77 |
| ‐ Hypertriglyceridemia | 11 (33.3) | 14 (45.2) | 14 (43.8) | 0.57 |
| Obesity—n (%) | 15 (45.5) | 19 (61.3) | 18 (56.3) | 0.43 |
| Metabolic syndrome—n (%) | 26 (78.8) | 26 (83.9) | 25 (78.1) | 0.82 |
| Cardiovascular disease—n (%) | 2 (6.1) | 2 (6.5) | 8 (25.0) | 0.04 |
| ‐ Coronary arterial disease—n (%) | 1 (3.0) | 1 (3.2) | 1 (3.1) | 1.00 |
| ‐ Previous CVA or TIA—n (%) | 1 (3.0) | 1 (3.2) | 6 (18.8) | 0.06 |
| ‐ Chronic peripheral arterial disease—n (%) | 0 (0.0) | 0 (0.0) | 2 (6.3) | 0.21 |
| ‐ Heart failure—n (%) | 0 (0.0) | 0 (0.0) | 0 (0.0) | = |
| Chronic kidney disease (GFR < 60 mL/min)—n (%) | 5 (15.2) | 3 (9.7) | 7 (21.9) | 0.39 |
| Proteinuria—n (%) | 4 (12.1) | 8 (25.8) | 10 (31.3) | 0.17 |
| Family history of CVD—n (%) | 21 (65.6) | 16 (53.3) | 21 (67.7) | 0.45 |
| Smoking—n (%) | 12 (36.4) | 14 (45.2) | 13 (40.6) | 0.77 |
| Fasting glucose—mg/dL (IQR) | 94 (31) | 91 (21) | 95 (21) | 0.81 |
| Total cholesterol—mg/dL (SD) | 180 (28) | 188 (32) | 180 (43) | 0.57 |
| HDL—mg/dL (IQR) | 40 (16) | 45 (17) | 38 (11) | 0.53 |
| LDL—mg/dL (IQR) | 108 (30) | 107 (28) | 100 (47) | 0.60 |
| Triglycerides—mg/dL (IQR) | 122 (47) | 140 (84) | 131 (118) | 0.81 |
| Creatinine—mg/dL (IQR) | 0.9 (0.4) | 0.9 (0.2) | 0.1 (0.3) | 0.90 |
| GFR—mL/min (SD) | 82.5 (19.6) | 82.2 (19.4) | 73.3 (20.1) | 0.11 |
| ADMA—µmol/L (IQR) a | 0.43 (0.14) | 0.57 (0.16) | 0.86 (0.19) | <0.001 |
Abbreviations: ABPM, ambulatory blood pressure monitoring; ADMA, asymmetric dimethylarginine; CVA, cerebral vascular accident; CVD, cardiovascular disease; GFR, glomerular filtration rate; IQR, interquartile range; SD, standard deviation; TIA, transient ischemic accident.
The serum ADMA was measure in visit 1.
Analyzing the evolution of the patients during visits (visit 1 to visit 6) according to resistant and non‐resistant hypertensive groups, there was a decrease in systolic and diastolic BP levels, mean systolic and diastolic BP in 24‐hour ABPM and ADMA levels in both groups (Table 3), to a greater extent in the group of resistant hypertensives (Figure 1).
TABLE 3.
Evolution of resistant and non‐resistant hypertensive patients during follow‐up (V1‐V6)
| Visit 0 | Visit 1 | Visit 3 | Visit 6 | P value | |
|---|---|---|---|---|---|
| Evolution of non‐resistant hypertensives (71) | |||||
| Systolic blood pressure—mm Hg (IQR) | 167 (14) | 132 (24) | 128 (17) | 129 (22) | 0.002 |
| Diastolic blood pressure—mm Hg (IQR) | 101 (10) | 85 (14) | 79 (12) | 80 (12) | 0.001 |
| Mean systolic blood pressure a —mm Hg (IQR) | 127 (16) | 124 (11) | 122 (15) | <0.001 | |
| Mean diastolic blood pressure a —mm Hg (IQR) | 78 (12) | 76 (9) | 76 (14) | <0.001 | |
| ADMA ‐ µmol/L (IQR) | 0.55 (0.19) | 0.49 (0.16) | 0.51 (0.11) | <0.001 | |
| Evolution of resistant hypertensives (15) | |||||
| Systolic blood pressure—mm Hg (IQR) | 167 (30) | 177 (18) | 152 (20) | 145 (27) | <0.001 |
| Diastolic blood pressure—mm Hg (IQR) | 112 (27) | 109 (32) | 97 (18) | 92 (16) | <0.001 |
| Mean systolic blood pressure a —mm Hg (IQR) | 162 (34) | 143 (19) | 132 (14) | <0.001 | |
| Mean diastolic blood pressure a —mm Hg (IQR) | 99 (23) | 87 (9) | 83 (14) | <0.001 | |
| ADMA – µmol/L (IQR) | 0.89 (0.34) | 0.79 (0.28) | 0.71 (0.28) | <0.001 | |
Abbreviations: ADMA, asymmetric dimethylarginine; IQR, interquartile range.
ABPM: ambulatory blood pressure monitoring,
FIGURE 1.
Intensity of reduction of blood pressure in each measure and intensity of reduction in ADMA values during follow‐up (V1‐V6)—Resistant and non‐resistant hypertensive patients
Additionally, a significant positive correlation was found between BP variation and serum ADMA variation during follow‐up (visit 1 to visit 6), in both hypertensive groups (Table 4/Figure 2).
TABLE 4.
Correlation coefficient of serum ADMA variation with changes in blood pressure during follow‐up (V1‐V6) in non‐resistant and resistant hypertension groups
| Non‐resistant hypertension | Resistant hypertension | |
|---|---|---|
| Δ Systolic BP (mm Hg) | 0.729* | 0.731* |
| Δ Diastolic BP (mm Hg) | 0.558* | 0.631* |
| Δ MSBP (mm Hg) | 0.548* | 0.644* |
| Δ MDBP (mm Hg) | 0.488* | 0.540* |
Abbreviations: BP, blood pressure; MDBP, mean diastolic blood pressure; MSBP, mean systolic blood pressure.
P < 0.05.
FIGURE 2.
Dot plots of serum ADMA variation with changes in blood pressure during follow‐up (V1‐V6) in non‐resistant and resistant hypertension groups
The evaluation of endothelial dysfunction by serum ADMA values above the median at V1 as a predictor of resistant hypertension throughout the follow‐up was performed by binary logistic regression. In the analysis, ADMA was an independent predictor of resistant hypertension even considering the variables sex, initial systolic BP, initial diastolic BP, type 2 DM, dyslipidemia, HDL cholesterol, metabolic syndrome, CKD, proteinuria, cerebrovascular disease, and number of pre‐study antihypertensive drugs (Table 5). In addition to serum ADMA, the number of pre‐study antihypertensive medications was also a predictor of resistant hypertension after adjustment for the multiple variables.
TABLE 5.
Logistic regression analysis for prediction of resistant hypertension based on initial serum ADMA level
| Outcome | OR | 95% CI | P value |
|---|---|---|---|
| Resistant hypertension | |||
| Not adjusted | 9.41 | 1.97‐44.89 | 0.005 |
| Adjusted for sex | 11.29 | 2.24‐56.85 | 0.003 |
| Adjusted for sex, initial SBP, initial DBP | 10.65 | 1.84‐61.53 | 0.008 |
| Adjusted for sex, initial SBP, initial DBP, type 2 DM | 10.92 | 1.88‐63.45 | 0.008 |
| Adjusted for sex, initial SBP, initial DBP, type 2 DM, DLP, HDL cholesterol | 11.13 | 1.87‐66.12 | 0.008 |
| Adjusted for sex, initial SBP, initial DBP, type 2 DM, DLP, HDL cholesterol, MS | 11.27 | 1.88‐67.50 | 0.008 |
| Adjusted for sex, initial SBP, initial DBP, type 2 DM, DLP, HDL cholesterol, MS, CKD, proteinuria | 18.32 | 2.15‐155.65 | 0.008 |
| Adjusted for sex, initial SBP, initial DBP, type 2 DM, DLP, HDL cholesterol, MS, CKD, proteinuria, cerebrovascular disease | 18.06 | 2.02‐161.49 | 0.010 |
| Adjusted for sex, initial SBP, initial DBP, type 2 DM, DLP, HDL cholesterol, MS, CKD, proteinuria, cerebrovascular disease, number of pre‐study antihypertensive drugs | 11.42 | 1.02‐127.71 | 0.048 |
Abbreviations: ADMA, asymmetric dimethylarginine; CKD, chronic kidney disease; DBP, diastolic blood pressure; DLP, dyslipidemia; DM, diabetes mellitus; MS, metabolic syndrome; SBP, systolic blood pressure.
4. DISCUSSION
This was a pre‐specified randomized intervention study involving a subpopulation from the ReHOT study, 3 which was developed with the aim of evaluating individuals with hypertension to identify resistant hypertension and standardize therapeutic regimens. In turn, our substudy was conducted to evaluate the relationship between resistant hypertension and endothelial function measured by serum ADMA in a subpopulation of 103 subjects from the ReHOT study followed up for 6 months.
Resistant hypertensive patients showed higher serum ADMA levels, higher prevalence of CKD and proteinuria, and CVA as well, corroborating the association of resistant hypertension with endothelial injury and cardiovascular events. 25 , 26 , 27 Regarding nephropathy and the occurrence of cerebrovascular disease, Muntner et al 25 showed an increase in the incidence of CVA, advanced CKD and CVD in 1870 resistant hypertensives compared to 12 814 non‐resistant hypertensive patients. In agreement with our results, Cuspidi et al 26 studied 105 individuals and found a greater carotid intima‐media thickening, a greater extent of carotid plaques, and greater urinary excretion of albumin in patients with resistant hypertension. In addition to the fact that they live with higher BP regimens, other factors seem to be involved in the development of target organ lesions in this population, since the study by Muntner et al 25 showed a higher incidence of CVD in controlled resistant hypertensive individuals in relation to non‐resistant hypertensives also controlled. These factors include prolonged hypertension and inadequate prior control, as well as sympathetic and RAAS hyperactivation, increased serum aldosterone production, endothelial dysfunction, reduced arterial compliance, and pre‐existing subclinical atherosclerotic disease. 27
Regarding endothelium and resistant hypertension, patients with a higher serum ADMA level at baseline had higher initial systolic and diastolic BP values and a higher prevalence of cardiovascular events. In addition, we demonstrated that ADMA was a predictor of the occurrence of resistant hypertension even after adjustment for sex, initial systolic BP, initial diastolic BP, type II DM, dyslipidemia, HDL cholesterol, metabolic syndrome, CKD, proteinuria, cerebrovascular disease and number of pre‐study antihypertensive drugs.
The association of ADMA with hypertension and its cardiovascular outcomes has been of interest to investigators over the years. The Coronary Artery Risk Determination Investigating the Influence of ADMA Concentration study (CARDIAC study) included 232 individuals with and without coronary artery disease (CAD), most of them being hypertensive (70%), and found a 20% higher ADMA concentration in coronary patients, along with an increase in risk of CAD greater than twofold for each increase of 1 µmol/L in serum ADMA. 28 This observation is in agreement with Nishiyama et al, 29 who showed an association between elevated serum ADMA level and hypertension, dyslipidemia, and ischemic stroke.
The association of serum ADMA level and the development of resistant hypertension demonstrated in our study was reinforced by the observation of its elevation in this population, as well as by its proportional variation with change in BP obtained with treatment, and this is explained through different mechanisms. The increase in ADMA level is involved in alterations in adipocyte function and oxidative stress pathways, in the increase in inflammatory response, and in the activation of RAAS and the autonomic nervous system, all linked to the increase in BP numbers. 20 , 21 , 22 , 23 , 30 , 31 , 32
Analyzing the evolution of individuals during follow‐up with antihypertensive treatment, a significant positive correlation was observed between BP numbers and serum ADMA in the groups studied, being the BP and ADMA variation more substantial in resistant hypertensives, as previously mentioned. These findings suggest that the more pronounced change in BP levels in the group of resistant hypertensives, which occurred due to the use of a greater number of classes of antihypertensive drugs, was related to alleviation of endothelial dysfunction. In agreement, Grassi et al performed bilateral renal denervation in resistant hypertensive patients and showed that the reduction in sympathetic activity after renal denervation was significantly associated with the drop in BP levels and decrease in serum ADMA. This finding highlights the relevant interface between sympathetic nervous system activity, endothelial dysfunction, and hypertension control. 32
Other demographic data from the analysis showed that the number of pre‐study antihypertensive drugs was higher in the population of resistant hypertensives (despite inadequate therapeutic adherence), and the time since diagnosis of hypertension did not differ between the groups. In relation to lipid profile, resistant hypertensive patients showed lower values of HDL cholesterol compared to non‐resistant hypertensives, even with equivalent rates of use of lipid‐lowering agents. A recent study by Aziz et al 33 analyzed 9340 diabetics and also showed an inverse relation of BP with HDL cholesterol. In turn, individuals in the third tertile of serum ADMA had higher LDL cholesterol values than the first and second tertiles, similar to that described by Böger et al. 34
In our study, there was a high pre‐study prevalence of pseudo‐resistance possibly due to inadequate therapeutic adherence (31.3%). Data from the literature show very variable rates of poor adherence (13.0%‐54.9%), depending on a series of factors related to personal, cultural, social, and economic aspects. 35 Aspects linked to poor adherence should be addressed in a multidisciplinary way in a population of hypertensive patients with the aim of optimizing therapy and reducing the incidence of CVDs. In the current study, strict control of medications dispensed and returned monthly ensured satisfactory adherence and reliable evaluation, excluding from the sample inadequate BP control due to non‐adherence.
The 24‐hour ABPM in three visits of the protocol allowed the evaluation of “white coat hypertension” and the existence of pseudo‐resistance, thus characterizing all individuals as true resistant hypertensives and not as apparent resistant hypertensives. In addition, the determination of resistant hypertension was by prospective analysis, which was more reliable. Finally, BP measurements were consistent with values obtained in ABPM, demonstrating the satisfactory quality of BP assessment in the clinic visits.
In a subanalysis of a randomized study of a cohort of hypertensive patients, we demonstrated an association between ADMA and resistant hypertension occurrence. In addition, we observed that improvement in BP obtained with pharmacological treatment was proportional to the reduction in ADMA level, suggesting a complementary role for this biomarker not only as a stratification tool regarding the occurrence of resistant hypertension, but also as a possible therapeutic target in this population.
CONFLICT OF INTEREST
There are no conflict(s) of interest/disclosure(s).
AUTHOR CONTRIBUTIONS
Daniel de Oliveira Beraldo: Substantial contributions to the conception or design of the work; acquisition, analysis, and interpretation of data for the work; drafting the work or revising it critically for important intellectual content; final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Cássio J. Rodrigues: Drafting the work and revising it critically for important intellectual content. Beata M. R. Quinto: Acquisition, analysis, and interpretation of data for the work; drafting the work and revising it critically for important intellectual content. Marcelo C. Batista: Final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
de Oliveira Beraldo D, Rodrigues CJ, Quinto BMR, Batista MC. Role of endothelial function determined by asymmetric dimethylarginine in the prediction of resistant hypertension: A subanalysis of ReHOT trial. J Clin Hypertens. 2020;22:2059–2068. 10.1111/jch.13936
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