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

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 3, May/June 2021

AFRICA

133

Vascular health assessment with flow-mediated

dilatation and retinal image analysis: a pilot study in an

adult population from Cape Town

Clara Marincowitz, Ingrid Webster, Corli Westcott, Nandu Goswami, Patrick De Boever, Gerald Seidel,

Hans Strijdom

Abstract

Aim:

Flow-mediated dilatation (FMD) and retinal vascular

analysis (RVA) may assist in predicting cardiovascular disease

(CVD) but are poorly characterised in South Africa. We

recorded baseline FMD and retinal vascular widths in healthy

participants, and investigated associations with cardiovascu-

lar risk factors.

Methods:

Endothelial function (measured with FMD), micro-

vascular structure (evaluated via fundus image analysis) and

major CVD risk factors were assessed in 66 participants from

Cape Town.

Results:

Median FMD% was 9.6%, with higher values in

females. Mean retinal arteriolar and venular widths were ~156

and ~250

m, respectively. FMD was not associated with

CVD risk factors. Hypertension was associated with narrower

retinal arterioles and venules.

Conclusions:

We report novel baseline FMD data in healthy

South African adults from the Western Cape, and show that

retinal microvascular calibres are associated with blood pres-

sure. Our baseline FMD and RVA data could serve as a refer-

ence for future studies in South Africa.

Keywords:

vascular health, endothelial function, flow-mediated

dilatation, retinal imaging, cardiovascular risk.

Submitted 14/5/20, accepted 2/10/20

Published online 13/11/20

Cardiovasc J Afr

2021;

: 133–140

www.cvja.co.za

DOI: 10.5830/CVJA-2020-046

Cardiovascular disease (CVD) accounts for an estimated

17.7 million deaths globally, of which more than 70% occur

in low- and middle-income countries such as South Africa.

The prevalence of CVD varies among different regions and

populations, and while a steady decline has been noted in many

high-income countries, this has not been the case in large parts

of sub-Saharan Africa.

In the Western Cape Province of South Africa, where

Cape Town is located, cardiovascular and cardiometabolic

diseases account for a large proportion of the primary causes

of death, including diabetes mellitus, ischaemic heart disease

and cerebrovascular disease.

According to the South African

Medical Research Council (SAMRC) Western Cape Mortality

Profile 2013, cardiovascular diseases accounted for 24.3% of all

deaths across all age groups in the province (compared to 23% of

deaths attributed to infectious diseases).

Previous studies have

reported a high prevalence of cardiovascular risk factors in Cape

Town populations, including type 2 diabetes mellitus, metabolic

syndrome, hypertension and smoking.

5,6

Many traditional cardiovascular risk factors have been

implicated in the development of endothelial dysfunction

(ED).

7,8

ED, characterised by a loss of vascular homeostasis

and reduced nitric oxide (NO) bioavailability, is an early

precursor of atherosclerosis and a marker and predictor of

CVD.

9-14

Flow-mediated dilatation (FMD) has become the gold-

standard non-invasive assessment tool for endothelial function

measurement in clinical research.

In previous studies, mainly

in populations from developed countries, FMD has been shown

to be associated with cardiovascular risk factors

11,16,17

and future

CVD events.

11,12,14

Yet, despite its potential as a clinical tool that

can serve as a surrogate marker of CVD risk, we are not aware

of studies utilising FMD in adult South African populations.

Retinal microvascular calibres, measured by non-invasive

fundus photography and computerised analysis, are associated

with long-termcardiovascularmortality and impaired endothelial

function.

18,19

The Multi-Ethnic Study of Atherosclerosis (MESA)

reported that smaller retinal arteriolar calibre (central retinal

arteriolar equivalent; CRAE) was associated with hypertension,

whereas larger arteriolar calibre was associated with diabetes,

current cigarette smoking and higher levels of plasma fibrinogen.

Larger retinal venular calibre (central retinal venular equivalent;

CRVE) has been shown to be associated with diabetes, current

cigarette smoking, obesity, dyslipidaemia and systemic markers

of inflammation and endothelial dysfunction.

There is a lack of retinal imaging studies in the South African

context, particularly in populations of the Western Cape. One

Cape Town-based study reported on retinal microvascular

calibres in a cohort of HIV-infected participants,

however, little

is known about the relationship between retinal microvascular

Centre for Cardio-metabolic Research in Africa, Division of

Medical Physiology, Stellenbosch University, Cape Town,

South Africa

Clara Marincowitz, MSc

Ingrid Webster, PhD,

iwebster@sun.ac.za

Corli Westcott, PhD

Hans Strijdom, MB ChB, PhD

Department of Physiology and Otto Loewi Research

Centre, Medical University of Graz, Austria

Nandu Goswami, MB BS, PhD

Health Unit, Flemish Institute for Technological Research

(VITO), Mol; Centre for Environmental Sciences, Hasselt

University, Diepenbeek; Department of Biology, University

of Antwerp, Wilrijk, Belgium

Patrick De Boever, PhD

Department of Ophthalmology, Medical University of Graz,

Austria

Gerald Seidel, PhD