Cardiovascular Journal of Africa: Vol 27 No 4 (July/August 2016)

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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 4, July/August 2016 262 AFRICA
Carotid characteristics of black South Africans with
five-year sustained hypertension
Melissa Maritz, Carla MT Fourie, Johannes M van Rooyen, Hugo W Huisman, Aletta E Schutte
Abstract
Introduction: An important feature of hypertension is a
reduction in large artery distensibility, which may be due to
structural and functional adaptations. Black populations are
particularly prone to the development of hypertension. We
therefore compared the carotid characteristics between five-
year sustained hypertensive and normotensive black South
Africans, and investigated how carotid characteristics relate
to cardiometabolic risk factors, inflammation, endothelial
activation and health behaviours.
Methods: We included HIV-free black South Africans who
were either consistently hypertensive (n = 351) or normoten-
sive (n = 241) from 2005 to 2010. We assessed carotid char-
acteristics, including intima–media thickness (IMT), disten-
sibility and lumen diameter with B-mode ultrasound, and
calculated Young’s elastic modulus, cross-sectional wall area
and beta-stiffness index. We measured the carotid dorsalis
pedis pulse-wave velocity, brachial and central systolic blood
pressure (cSBP) and determined metabolic, inflammatory and
endothelial activation markers from blood samples. Health
behaviours were reported in questionnaires.
Results: The hypertensive group presented with higher brach-
ial and central blood pressure, thicker IMT and stiffer carotid
arteries (all p < 0.001). However, after adjustment for cSBP
but not mean arterial pressure (MAP), all significant differ-
ences in carotid characteristics were lost. The carotid thick-
ness measurements did not differ after adjustment for MAP.
After adjustment, metabolic, inflammatory and endothelial
activation markers did not differ between the two groups.
Conclusion: Our results suggest that besides structural chang-
es, functional adaptations are also involved in deterioration
of the carotid wall characteristics of hypertensive black South
Africans. These results highlight the importance of proper
hypertension control in Africa.
Keywords: ethnicity, large artery, stiffness, distensibility, hyper-
tension, central pressure
Submitted 30/10/15, accepted 5/5/16
Cardiovasc J Afr 2016; 27: 262–269
DOI: 10.5830/CVJA-2016-059
Worldwide, cardiovascular disease is the leading cause of
death.1 Arterial stiffness is implicated in the development of
cardiovascular disease, which results in stroke, coronary heart
disease and heart failure.2,3 Arterial stiffness refers to the reduced
ability of an artery to expand and recoil with pressure changes,
and the arterial distensibility is a measure of vessel stiffness.4
Decreased distensibility may raise central systolic blood pressure
(cSBP) and consequently decrease the amplification of pulse
pressure.5,6 This results in inadequate coronary perfusion,
increased afterload on the heart, as well as an increased pulsatile
load on the microcirculation.3
The artery is able to resist strain during blood pressure
increases via recruitment of collagen fibres in the arterial wall,7
but sustained high pressure predisposes the vessel to progressive
changes in the wall shape and composition, ultimately leading
to several clinical complications such as arterial fibrosis and
stiffening.8,9
Recently, van Sloten et al . reported that in a European
population, carotid artery stiffness independently predicts
incident cardiovascular (CV) events and all-cause mortality.3
The higher incidence of stroke, heart failure and renal failure in
black populations are a consequence of the higher prevalence of
hypertension,10,11 and arterial stiffness 12,13 in black compared to
white populations.
Despite the high prevalence of hypertension and stroke
among black South Africans,14 there is limited knowledge
on carotid wall properties in this population. We therefore
compared the characteristics of the carotid arteries between
normotensive and five-year sustained hypertensive black
individuals, along with brachial and central blood pressure
and conventional cardiometabolic risk factors, markers of
inflammation, endothelial activation and health behaviours.
Methods
This sub-study forms part of the South African leg of the
multi-national Prospective Urban and Rural Epidemiology
(PURE) study.15 The participants of the PURE-SA study were
from urban and rural localities in the North West Province,
and baseline data collection took place in 2005 (n = 2 010
participants), while follow-up data was collected five years later,
in 2010 (n = 1 288 participants). For this sub-study we included
only the HIV-free black participants with two consecutive (2005,
2010) blood pressure measurements in either the hypertensive or
normotensive range (n = 592 participants), consisting of a group
of five-year sustained normotensive (n = 241participants) and
hypertensive (n = 351 participants) black South Africans (Fig. 1).
The Health Research Ethics Committee of the North-West
University approved the protocol of the PURE-SA study, as
well as this sub-study (ethics number: NWU-00016-10-A1),
and it complies with the Declaration of Helsinki. Participants
completed structured demographic, lifestyle and physical
Hypertension in Africa Research Team (HART), North-West
University, Potchefstroom, South Africa
Melissa Maritz, MSc
Carla MT Fourie, PhD,
Johannes M van Rooyen, DSc
Hugo W Huisman, PhD
Aletta E Schutte, PhD
MRC Research Unit for Hypertension and Cardiovascular
Disease, North-West University, Potchefstroom, South Africa
Aletta E Schutte, PhD