Cardiovascular Journal of Africa: Vol 32 No 3 (MAY/JUNE 2021)

29 / 66

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 3, May/June 2021 AFRICA 139
African population. Despite this, it was interesting to note the
comparability of our baseline FMD and retinal measurements
with those from previously published studies.
The FMD procedure is technically challenging, requires
thorough training and may suffer from operator-dependent
variability.24,25,47 We would therefore recommend the use of
computerised vessel edge-detecting/wall-tracking software
systems for future studies, as computerised analysis has been
suggested to improve the reproducibility.48 Although we have
addressed this as far as possible, as described in detail in
the methods section, these potential constraints need to be
acknowledged.
Conclusion
We present here, for the first time, FMD data in an apparently
healthy adult South African cohort from the Western Cape
Province. In this cohort, a median FMD of 9.6% was recorded,
which compares reasonably well with previously published
data in different populations, mainly from Europe and North
America. The findings also confirmed previous reports that
FMD values appear to be lower in males compared to females.
It is proposed that the current FMD values could serve as a
starting point of reference for future studies from South Africa
and the sub-Saharan African region.
The retinal arteriolar and venular calibre measurements
recorded in our cohort are reasonably comparable to those
from other studies and will serve to add to a small but growing
database of published retinal microvascular data from other
South African researchers. In agreement with the literature,
narrower retinal microvascular calibres in our cohort were
associated with elevated blood pressure, and in a novel finding
in the South African context, we showed that participants
presenting with retinal tortuosity had increased diastolic blood
pressure compared to those without tortuosity. These findings
further support the use of non-invasive retinal image analysis in
cardiovascular epidemiology research.
We thank the EndoAfrica research team and field workers, in particular the
research nursing staff (Charmaine Abrahams, Shirley McAnda and Susan
van Zyl) for their contributions towards recruitment and data collection.
This work was funded under the ERAfrica programme of the EU 7th
Framework Programme. Fundingwas disbursed via theDepartment of Science
and Technology in South Africa (contract number DST/CON 0077/2014),
the Belgian Science Policy in Belgium (contract number BL/67/eranet03),
and Österreichische Agentur für internationale Mobilität und Kooperation
in Bildung, Wissenschaft und Forschung, OeAD GmbH (ÖAD) in Austria
(grant number: KEF-Projekt P202). HS was supported by the National
Research Foundation of South Africa (grant reference: CSUR13082330472).
IW was supported by the National Research Foundation (NRF) of South
Africa Research Career Advancement (RCA) award.
References
1. WHO. Cardiovascular diseases (CVDs) fact sheet [Internet]. World
Health Organisation Media Centre, 2017.
tre/factsheets/fs317/en/
2. Roth GA, Johnson C, Abajobir A, Abd-Allah F, Abera SF, Abyu G, et
al. Global, regional, and national burden of cardiovascular diseases for
10 causes, 1990 to 2015. J Am Coll Cardiol 2017; 70(1): 1–25.
3. Statistics SA. Mortality and causes of death in South Africa, 2016:
Findings from death notification [Internet]. Statistical Release P0309.3.
Pretoria, 2018.
4. Groenewald P, Zinyakatira N, Neetlin I, Msemburi W, Daniels J,
Vismer M, et al. Western Cape mortality profile 2013: mortality trends
2009–2013 [Internet]. Cape Town: South African Medical Research
Council, 2016, Vol 11: 1–12.
files/2017-05-26/WC2013MortalityReport.pdf
5. Erasmus RT, Soita DJ, Hassan MS, Blanco-Blanco E, Vergotine Z,
Kengne AP, et al. High prevalence of diabetes mellitus and metabolic
syndrome in a South African coloured population: Baseline data of
a study in Bellville, Cape Town. S Afr Med J 2012; 102(11): 841–844.
6. Laurence EC, Volmink J, Esterhuizen TM, Dalal S, Holmes MD. Risk
of cardiovascular disease among teachers in Cape Town: Findings of the
South African PaCT pilot study. S Afr Med J 2016; 106(10): 996–1001.
7. Mudau M, Genis A, Lochner A, Strijdom H. Endothelial dysfunction :
the early predictor of atherosclerosis. Cardiovasc J Afr 2012; 23(4):
222–231.
8. Li H, Horke S, Förstermann U. Oxidative Stress in Vascular Disease and
its Pharmacological Prevention. Trends in Pharmacological Sciences .
Elsevier Current Trends, 2013; 34: 313–319.
com/science/article/pii/S0165614713000485
9. Nabel EG, Braunwald E. A Tale of coronary artery disease and myocar-
dial infarction. N Engl J Med 2012; 366(1): 54–63.
10. Barquera S, Pedroza-Tobías A, Medina C, Hernández-Barrera L,
Bibbins-Domingo K, Lozano R, et al . Global overview of the epide-
miology of atherosclerotic cardiovascular disease. Arch Med Res 2015;
46(5): 328–338.
11. Rossi R, Nuzzo A, Origliani G, Modena MG. Prognostic role of flow-
mediated dilation and cardiac risk factors in post-menopausal women. J
Am Coll Cardiol 2008; 51(10): 997–1002.
12. Ras RT, Streppel MT, Draijer R, Zock PL. Flow-mediated dilation and
cardiovascular risk prediction: A systematic review with meta-analysis.
Int J Cardiol 2013; 168: 344–351.
13. O’Neal WT, Efird JT, Yeboah J, Nazarian S, Alonso A, Heckbert SR,
et al. Brachial flow-mediated dilation and incident atrial fibrillation the
multi-ethnic study of atherosclerosis. Arterioscler Thromb Vasc Biol 2014;
34(12): 2717–2720.
14. Shechter M, Shechter A, Koren-Morag N, Feinberg MS, Hiersch L.
Usefulness of brachial artery flow-mediated dilation to predict long-term
cardiovascular events in subjects without heart disease. Am J Cardiol
2014; 113(1): 162–167.
15. Deanfield JE, Halcox JP, Rabelink TJ. Endothelial function and dysfunc-
tion: Testing and clinical relevance. Circulation2007; 115(10): 1285–1295.
16. Maruhashi T, Soga J, Fujimura N, Idei N, Mikami S, Iwamoto Y, et
al. Relationship between flow-mediated vasodilation and cardiovascu-
lar risk factors in a large community-based study. Heart 2013; 99(24):
1837–1842.
17. Celermajer DS, Sorensen KE, Bull C, Robinson J, Deanfield JE.
Endothelium-dependent dilation in the systemic arteries of asympto-
matic subjects relates to coronary risk factors and their interaction. J Am
Coll Cardiol 1994; 24(6): 1468–1474.
18. Al-Fiadh AH, Farouque O, Kawasaki R, Nguyen TT, Uddin N,
Freeman M, et al. Retinal microvascular structure and function in
patients with risk factors of atherosclerosis and coronary artery disease.
Atherosclerosis 2014; 233(2): 478–484.
19. Wong TY, Klein R, Nieto FJ, Klein BEK, Sharrett AR, Meuer SM,
et al. Retinal microvascular abnormalities and 10-year cardiovascular
mortality: A population-based case-control study. Ophthalmology 2003;
110(5): 933–940.