1,720,977 research outputs found
African prospective study on the early detection and identification of cardiovascular disease and hypertension
No full textMaster of Health Sciences in Cardiovascular Physiology, North-West University, Potchefstroom Campus, 2019Motivation: There are number of factors that are known to contribute to the elevation of blood pressure
(BP) and the subsequent increase in cardiovascular risk. One of the most prominent systems
is the renin-angiotensin-aldosterone system (RAAS), which controls electrolyte and fluid
volume. Components of the RAAS (prorenin, renin, angiotensinogen, angiotensins,
angiotensin-converting enzyme (ACE) and aldosterone) have been linked to cardiac and
vascular remodelling and subsequent cardiovascular disorders such as hypertension,
atherosclerosis and cardiac hypertrophy. Pulse pressure (PP) has been established as a
significant marker of cardiovascular risk. Furthermore, pulse pressure amplification (PPA), the
difference between central PP and brachial PP, has in recent years shown the potential to be
a risk factor for cardiovascular disease (CVD). It is thus clear that in order to understand the
development and progression of hypertension and its associated risk, it is important to
recognise that BP varies across the vasculature and this complexity may influence the relation
with BP regulating pathways such as the RAAS. Previous studies investigating the
associations between hemodynamic factors and the RAAS focused largely on older and highrisk
populations. It is therefore unclear whether any adverse associations are already present
between the RAAS and PP as well as PPA in young populations. It therefore, becomes
imperative to investigate the link between PP and its amplification in young healthy populations
in order to broaden understanding and identify possible areas of intervention to prevent the
development of cardiovascular disease.
Aim: The main aim of this study was to investigate the relationship of PP and its amplification (PPA)
with RAAS components including prorenin, renin, aldosterone and ACE in young black and
white, men and women. Methods: The study population consisted of 752 participants from the African-PREDICT study.
Demographic information was obtained through the general health questionnaire. The
following anthropometric measurements were also taken: height, weight, body mass index,
waist circumference, weight to height ratio was then subsequently calculated. The ActiHeart
device (CamNtech Ltd., England, UK) was used to calculate total energy expenditure (TEE)
over a period of 7 days. Brachial blood pressure was measured with the Dinamap Procare
100 Vital signs Monitor (GE Medical Systems, Milwaukee, USA) with GE Critikon latex-free
Dura-Cuffs (medium and large). The brachial artery was used on both left and right arms and
the measurements were performed in duplicate at 5 minutes intervals. Brachial PP was then
calculated by subtracting diastolic BP (DBP) from systolic BP (SBP) using the mean of both
the right and left arms. The SphygmoCor XCEL device (SphygmoCor XCEL, AtCor Medical,
Sydney, Australia) was used to produce an arterial waveform from which pulse wave analysis
was used to obtain central SBP (cSBP) and central PP (cPP). PPA was the classified as
bPP/cPP along with these pulse wave velocity (PWV) was also captured at the right carotid
and femoral arterial pulse points. Twenty-four-hour BP measurements were also performed
(heart rate (HR), DBP, SBP and PP). Masked hypertension was classified as clinical BP
measurements within normal limits (<140/90 mm Hg) and 24-hour BP classed as hypertensive
(SBP>140 mm Hg and/or a DBP>90 mm Hg). Dipper status was determined according to
ambulatory BP with the formula used by American Heart Association. The following
concentrations for biological and biochemical variables were determined: Serum creatinine,
cotinine, C-reactive protein (CRP), total and high-density lipoprotein cholesterol, glucose and
gamma glutamyltransferase (GGT) as well as urinary sodium, potassium and chloride, then
the Na/K ratio was calculated. Estimated glomerular filtration rate (eGFR) was calculated using
the Chronic Kidney Disease Epidemiology (CKD-EPI) formula. Serum samples were analysed
for total renin, aldosterone as well as ACE. EDTA samples was used for analysis of prorenin.
Results: Of the total population, 16.8% were found to have masked hypertension of this, 20.2% were
white and 13.6% were black (p=0.02). The white group was older when compared to the black
group (p˂0.001). When looking at the RAAS components, the white group showed higher
prorenin and aldosterone levels (both p˂0.001), whereas the black group showed higher total
renin (p=0.05), eGFR (p˂0.001) and sodium-to-potassium ration (p<0.001). When looking at
the cardiovascular measurements; the black group had higher cSBP (p˂0.001) and DBP
(p=0.002), on the other hand, the white group had a higher 24-hour SBP and 24-hour PP (both
p˂0.001) but a lower heart rate (p˂0.001). No significant differences in PPA were observed.
A lower percentage of the black group presented as nocturnal dippers compared to the white
group (46.7% vs 64.3.5, p<0.001). Though, the white group had a higher TEE they presented
with higher weight, BMI and waist circumference (all p˂0.001) as compared to the black group.
The white group also had higher glucose (p˂0.001) and total cholesterol (p=0.001) levels.
When comparing the men and women within the black and white group, black men presented
with higher office bPP, 24-hour PP, cSBP and cPP (all p≤0.001)) as well as PPA (p=0.007),
but a lower 24-hour HR (p<0.001) as compared to black women. White men also had higher
bPP and, 24-hour PP, cSBP, cPP and PPA (all p<0.001), but a lower HR (P<0.001). A higher
percentage of black men (18.9% vs 10.21%) and white men (35.6% vs 7.92%) had masked
hypertension (p=0.02 and p<0.001 respectively) as compared to their female counterparts.
When comparing the RAAS components, black women had lower total renin (p<0.001),
prorenin (p<0.001) and ACE (p=0.001) levels than the black men. White women had lower
renin (p<0.001), prorenin (p=0.005) and eGFR (p=0.006) but had higher aldosterone levels
(p<0.001) than black men. In the forward stepwise multiple regression analyses an association
between cPP with ACE (β=0.10, p=0.001) was observed only in the total group. A negative
association between total renin and bPP (β=-0.20, p=0.05), as well as a positive association
between aldosterone and PPA (β=0.18, p<0.001) were observed in black women, whereas in
white women only a negative association between ACE and PPA (β=-0.19, p<0.001) was
observed. Conclusions: cPP associated positively with ACE in the total group and PPA negatively with ACE in white
women. PPA associated positively with aldosterone and negatively with renin in black women.
Our results suggest that that at a young age, the RAAS is adversely associated with
haemodynamics and this may translate to increased ethnic and gender specific cardiovascular
risk later in lifeNational Research Foundation (NRF)Master
The renin-angiotensin-aldosterone-system and left ventricular mass in young black and white adults: the African-PREDICT study
Full text linkM Health Sciences (Cardiovascular Physiology), North-West University, Potchefstroom CampusMotivation. The renin-angiotensin system (RAS) is a central regulatory component implicated in sodium and water homeostasis that affects blood volume and pressure. Dysregulation of this system results in increased blood pressure (BP) and may contribute to the development of left ventricular hypertrophy (LVH). In addition to the RAS and BP, factors such as increased age, sex, black ethnicity and a low socio-economic status (SES) also contribute to left ventricular remodelling. In the South African context low SES may be even more important as it affects 55.5% of the population with a large proportion (63.4%) of them being young and unemployed. It is therefore important to investigate RAS-related increases in left ventricular mass (LVM) along with the possible influence low SES may have in young South Africans. Aim. This study investigated the relationship between LVMi (index) and the RAS components in young (20-30 years) healthy participants of the African-PREDICT study while taking factors such as SES, ethnicity and sex into consideration. Methods. This study used cross-sectional data from 1 186 black and white men and women divided into low and high SES groups. Demographic data including age, sex, ethnicity, skill level (classified according to the South African Standard Classification of Occupation (SASCO), education and income were collected using various questionnaires. Socio-economic status was calculated using a point system adapted from the Kuppuswamy's Socioeconomic Status Scale. Anthropometric measurements and physical activity were measured. Cardiovascular measurements included clinic BP, 24h ambulatory BP, total peripheral resistance and echocardiography which were used to determine LVM - normalised for body surface area to derive LVMi. The RAS Fingerprint® was measured with an ultra-pressure-liquid chromatography tandem-mass spectrometry (LC-MS/MS) method. A wide range of other biochemical markers considered as cardiovascular disease risk markers were also analysed. Results. Aligned with the aim of this study it was determined whether LVMi is associated with components of the RAS. LVMi associated inversely and independently with plasma renin activity (ꞵ=-0.168; P=0.017), angiotensin I (ꞵ=-0.155; P=0.028) and angiotensin II (ꞵ=-0.172; P=0.015), only in black women with low SES. No associations were evident between LVMi and components of the RAS in black women with high SES, or white women, black or white men, independent of SES. Conclusion. This finding suggests that multiple factors may play a role in the development of increased LVM, including suppressed RAS, raised BP, female sex, black ethnicity and a low socio-economic environment.Master
Left ventricular diastolic function and its relationship with the renin-angiotensin-aldosterone system and amino-terminal prohormone B-type natriuretic peptide: the African-PREDICT study
Full text linkMHSc (Cardiovascular Physiology), North-West University, Potchefstroom CampusMotivation: The association of left ventricular (LV) diastolic function markers with the renin-angiotensin-aldosterone system (RAAS) and amino-terminal prohormone B-type natriuretic peptide (Nt-proBNP) in older and diseased populations are known. Our study was motivated by the lack of evidence in young, healthy adults regarding the associations of LV diastolic function markers with the RAAS and Nt-proBNP to establish early manifestations of cardiovascular compromise. Aim: To compare the cardiovascular characteristics along with the RAAS and Nt-proBNP levels, as well as to explore the associations of LV diastolic function with the RAAS and Nt-proBNP in young apparently healthy black and white South Africans. Methodology: Cross-sectional data of the first 400 participants (age between 20—30 years) from the African prospective study on the early detection and identification of cardiovascular disease and hypertension (African-PREDICT) was used in this sub-study. Participants with missing data (n=55), as well as individuals with identified left or right bundle branch block (n=9) were excluded. This study obtained approval from the Health Research Ethics Committee of the North-West University (NWU-00032-17-A1) and complied with the Declaration of Helsinki (2008). Ambulatory blood pressure was measured along with a 12-lead electrocardiogram. A standard transthoracic echocardiography procedure was followed, to acquire variables of LV diastolic function including: E/A (peak early filling E-wave/late diastolic filling A-wave) ratio, E/é (mitral peak velocity of early filling/early diastolic mitral annular velocity) ratio, left atrium to aortic root ratio (LA/Ao) and LV end-diastolic volume. Anthropometric measurements included body height and weight, while body mass index and body surface area were additionally calculated. Among other biomarkers, renin, prorenin, aldosterone and Nt-proBNP were analyzed. Results: Age and body composition were lower in the black group (all p<0.005) compared to the white group. Blood pressures were comparable between the groups. The LV end diastolic volume was lower in the black (p<0.0001) compared to the white group. The E/A and E/e' ratios were higher in the black (both p<0.05) compared to the white group, whereas heart rate and the LA/Ao ratio were similar in both groups. Total renin was higher in the black group (p=0.010), whereas aldosterone and Nt-proBNP were lower in the black group (all p<0.005) compared to the white group. In multiple regression analysis with covariates age, sex, body surface area (except for LV end-diastolic volume), systolic blood pressure, heart rate, gamma-glutamyl-transferase, C-reactive protein, cotinine, total cholesterol-to-high density lipoprotein cholesterol ratio, estimated glomerular filtration rate and activity energy expenditure the following associations were found. The E/A ratio associated positively with prorenin in the black group (adj. R2=0.201; β=0.15; p=0.049) and total renin in the white group (adj. R2=0.131; β=0.16; p=0.042), whereas the LA/Ao ratio associated positively with prorenin (adj. R2=0.050; β=0.18; p=0.032) in the white group only. No associations were evident between markers of LV diastolic function and Nt-proBNP in either group. General conclusion: In conclusion, our study indicated that diastolic function markers associated adversely with components of the RAAS, in both groups. Our findings may indicate that higher E/A and LA/Ao ratios may be attributed to potential changes in the RAAS. This may suggest that both groups are prone to premature RAAS modifications, probably due to lifestyle risk factors, which may lead to future diastolic dysfunction.Master
Growth differentiating factor-15 and its association with traditional cardiovascular risk factors: the African-PREDICT study.
No full textBackground and aims
Growth differentiating factor-15 (GDF-15) is a stress-induced and cardio-protective cytokine, reported to be influenced by a number of cardiovascular risk factors. In older adults, GDF-15 associated with age, black ethnicity and smoking. It is important to determine if GDF-15 could potentially be used as an early marker of cardiovascular disease, especially in young populations. We investigated whether GDF-15 associated with traditional cardiovascular risk factors (age, sex, ethnicity, blood pressure (BP), socio-economic status, waist-to-hip ratio, cholesterol, physical inactivity, smoking and alcohol use) in young apparently healthy adults.
Methods and results
We included 1189 black and white participants (aged between 20 and 30 years). Questionnaires were used to collect demographic and physical activity data. We measured serum GDF-15, and performed 24-h ambulatory BP and pulse wave analysis. The following risk factors increased with increasing GDF-15 quartiles: age, black ethnicity, central systolic BP, 24-h diastolic BP, tumour necrosis factor-alpha, lipids, cotinine, smoking and alcohol use (all p trend ≤ 0.013). Socio-economic status and physical activity (p trend ≤ 0.014) were the lowest in the highest quartile. In multi-variable adjusted regression analyses GDF-15 associated with central systolic BP (β = 0.076; p = 0.027), age (β = 0.096; p = 0.006), low socio-economic status (β = −0.12; p = 0.003), physical inactivity (β = −0.18; p < 0.0001), tumour necrosis factor-alpha (β = 0.28; p < 0.0001) and cotinine (β = 0.12; p < 0.0001).
Conclusion
In young adults, GDF-15 associated independently with multiple traditional cardiovascular risk factors including higher central systolic blood pressure, older age, lower socio-economic status, physical inactivity, inflammation and smoking. These results suggest that GDF-15 is a promising biomarker for early identification of cardiovascular ris
Ethnicity and arterial stiffness
Full text linkEarly vascular aging reflects increased arterial stiffness of central blood vessels at young chronological ages and
powerfully predicts cardiovascular events and mortality, independent of routine brachial blood pressure and other risk factors.
Since ethnic disparities exist in routine blood pressure, in hypertension and cardiovascular outcomes, this review evaluates major
studies comparing arterial stiffness through the life course between different ethnic groups or races (which have no biological
definition)—in children, adolescents, young, and middle-aged adults and the very elderly. Most report that compared with white
European-origin samples, populations of black African descent have increased central arterial stiffness throughout different life
stages, as well as a more rapid increase in arterial stiffness at young ages. Exceptions may include African Caribbean origin people
in Europe. Differences in vascular structure and function are clearest, where obesity, socioeconomic, and psychosocial factors are
most marked. Few studies evaluate a wider spectrum of ethnic groups or factors contributing to these ethnic disparities. Genetic
effects are not obvious; maternal risk and intergenerational studies are scarce. Nevertheless, across all ethnic groups, for given
levels of blood pressure and age, some people have stiffer central arteries than others. These individuals are most at risk of
vascular events and mortality and, therefore, may benefit from early, as yet untested, preventive action and treatmen
Associations of central and peripheral blood pressure with the renin-angiotensin-aldosterone system in healthy young adults: the African-PREDICT study
No full textThis study investigated associations of brachial and central blood pressure (BP) with detailed renin-angiotensin-aldosterone system (RAAS) components in a healthy young population stratified according to ethnicity and sex. We included healthy black men (n = 285) and women (n = 304) and white men (n = 278) and women (n = 305) aged 20–30 years old. We derived central systolic BP (cSBP), measured clinic and 24-h systolic and diastolic BP. Aldosterone and equilibrium angiotensin levels were assessed and used for calculating angiotensin-derived markers for plasma renin activity (PRA-S, Angiotensin I + Angiotensin II), angiotensin-converting enzyme (ACE-S, Angiotensin II/Angiotensin I), and two markers for adrenal effects of angiotensin II, the aldosterone-to-renin ratio (ARR-S, Aldosterone/PRA-S) and the aldosterone-to-angiotensin II-ratio (AA2-R, Aldosterone/Angiotensin II). Young black men and women presented with lower RAAS components and higher cSBP compared to their white counterparts (all p ≤ 0.001). In multivariable-adjusted regression analyses, positive associations of cSBP with ARR-S and AA2-R and negative associations with PRA-S and angiotensin II were found for black women (all p ≤ 0.001); this pattern was also observed for 24-h and clinic BP (p ≤ 0.045). A similar trend of RAAS associations was present in black men but only for clinic BP (all p ≤ 0.047). In white men, negative associations between clinic SBP and PRA-S, angiotensin II and aldosterone were detected (all p ≤ 0.048). No associations were observed in white women. Positive associations of central and peripheral BP with the ratio of aldosterone to PRA-S and angiotensin II only in healthy, young black adults suggest that relative aldosterone excess may contribute to early hypertension development in this grou
Left ventricular mass independently associates with 24-hour sodium excretion in young masked hypertensive adults: the African-PREDICT study
No full textBackground
Due to the known contribution of excess sodium intake on elevations in blood pressure, salt reduction regulations are being introduced in countries all over the world. To study the contribution of sodium intake on cardiovascular disease development, we determined whether left ventricular mass associates with sodium excretion in young adults free from overt cardiovascular disease and those with masked hypertension.
Methods
We included 681 participants (41% men and 50% black) in a cross-sectional analysis from the African-PREDICT study with complete 24-hour urine collections and successful ambulatory blood pressure monitoring (>70% valid readings). The participants were categorized as normotensive (n = 534) or masked hypertensive (n = 147). In addition, we determined left ventricular mass index (LVMI) along with traditional risk factors.
Results
Masked hypertensive individuals had higher sodium excretion (149 vs. 128 mmol/L/day) and LVMI (78.1 vs. 69.6 g/m2) than normotensives. In single, partial and multiple regression analyses, LVMI independently associated with higher sodium excretion in the total group of young adults (β = 0.089; p = 0.011). This result was also evident among masked hypertensives (β = 0.215; p = 0.008), but not in normotensives (β = 0.054; p = 0.134).
Conclusion
Our results indicated that higher sodium excretion (reflecting a higher salt intake) may contribute to increased left ventricular mass, potentially driven by the early development of masked or undetected hypertensio
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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