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VOLUME 13 NUMBER 2 • DECEMBER 2016
89
SA JOURNAL OF DIABETES & VASCULAR DISEASE
REVIEW
Physiologically or pharmacologically induced stress tests are
helpful to differentiate cardiac from non-cardiac aetiology of chest
pain in patients with inducible ischaemia due to obstructive coronary
artery disease. The safe performance of provocative stress testing
and IVUS requires appropriate professional competence, careful
selection of patients and availability of resuscitation equipment in
cases of adverse events during testing. Low autopsy rates often
coupled with uncertified deaths outside health facilities exacerbate
the situation.
This lack of evidence on IHD in SSA is erroneously reinforced by
beliefs that IHD affects only the wealthy and elderly, that it arises
from freely acquired risks and that its management is expensive,
ineffective and of a lower priority than infectious diseases such as
HIV/AIDS, tuberculosis, malaria, and a number of neglected tropical
diseases. Moreover, there are strong opinions that IHD in SSA
affects mainly small westernised populations and that it is a less
serious cause of morbidity and mortality.
2
Some of these authorities
are of the opinion that cardiovascular risk factors in groups of older
Africans, including obesity, diabetes and metabolic disorders are
virtually non-existent and that IHD is bound to be a less serious
threat, as there are very few black populations in the older age
category.
2
Others have expressed disbelief of the potential epidemic of IHD
in SSA in the next few decades and contend that resources should
be appropriated to the current threats, particularly rheumatic
heart disease and cardiomyopathies.
3
Additional setbacks accrue
from lack of appropriate resources and skills to guide and
direct epidemiological studies of ischaemic heart disease; crisis
management often focused on acute conditions and infectious
diseases; and perpetual uncoordinated approaches to health issues
that are often reactionary, leading to neglect of NCDs.
The majority of the 57 countries in the world with critical
shortages of health workers are in SSA. The total health workforce
density in SSA is the lowest in the world with just 2.3 per 1 000
population, compared to 18.9 and 24.8 per 1 000 population in
Europe and the Americas, respectively. In fact, SSA has only 4% of
the global number of health workers but 25% of the global burden
of disease.
4
Sadly, some of the myths regarding IHD in SSA are fueled by the
notion that the various cardiovascular disease (CVD) risk factors,
although prevalent in urban black Africans, appear to exert their
influence in a far less noxious manner than is the case in most
Western populations. Also that lipid profiles are generally less
atherogenic, leading to suggestions of the ‘genetic resistance’ of
black Africans to IHD.
The view that IHD is rare in SSA is rooted in old beliefs arising
from earlier authors such as Cook5 and Donnison,6 and needs to
be effectively demystified. Firstly, atherothrombotic cardiovascular
disease is a global problem that afflicts every community regardless
of region, ethnicity or gender. The burden of cardiovascular
disease is increasing rapidly in Africa and it is now a public health
problem throughout the African region, particularly hypertension,
stroke, cardiomyopathies, and not least, ischaemic heart disease.
Rheumatic heart disease is still a major concern.
Scarcity of data on IHD and the non-existence of epidemiological
surveillance systems for cardiovascular diseases in most of SSA
should not be construed to mean rarity of the disorder. INTERHEART,
a global case–control study of acute myocardial infarction (AMI)
of 28 000 subjects in 52 countries showed that nine risk factors
accounted for 90% of population-attributable risk (PAR) in all
regions.
7
These risk factors included hypertension, diabetes, central
obesity, dyslipidaemia, physical inactivity, psychological stress,
tobacco use, inadequate intake of fruits and vegetables, and
inadequate or no alcohol intake.
Although the results of the INTERHEART study have been
challenged on account of it being a case–control study rather than
a prospective study, the major contributing individual risk factors
for acute myocardial infarction are generally consistent across the
globe and reminiscent of the conclusions of the original Framingham
Heart study several decades ago, as well as its 30-year follow-up
study.
8,9
Some have questioned the reliability of information on
some of the cardiovascular risk factors used in the INTERHEART
study, for example history of hypertension and diabetes mellitus,
and have raised concerns about recall bias regarding diet and
psychosocial factors in the setting of devastating effects of index
acute myocardial infarction on a person’s mental state. In some
parts of SSA, haemoglobinopathies such as haemoglobin S or
haemoglobin C might contribute to ischaemic heart disease due to
vasoocclussive crises.
Secondly, despite variations in genetic susceptibilities to IHD in
different ethnic groups, the common environmental and traditional
coronary heart disease risk factors pathogenetically play their roles
through a common final pathway in the development of clinical
atherosclerotic heart disease in all ethnic groups. Marked regional
differences in the impact of CVDs merely reflect a myriad of
factors, among them the level of care, quality of health statistics,
and differences in stages of socio-economic, nutritional and
epidemiological transition between countries, communities and
even between individuals.
Thirdly, as societies undergo ‘urbanisation’, risk-factor levels
for CVDs including IHD increase. For instance, only about 5% of
Africans were urbanised by 1900. At the start of independence in
the 1950s, 14.7% of inhabitants of Africa were urban. In 2000,
the urbanisation rate had risen to 37.2%, and by 2015 the rate is
expected to hit 45.3% with continually high rates of rural–urban
migrations across Africa.
10
The burden of cardiovascular risk factors in SSA
Hypertension
Systemic arterial hypertension poses a special challenge in SSA,
with immense socio-economic implications because of its high
prevalence, especially in urban dwellers. Hypertension is arguably
the most powerful cardiovascular risk factor in the African context
and has been declared by the African Union as one of the greatest
health challenges to the continent other than HIV/AIDS. The problem
is compounded by lack of awareness, frequent under-diagnosis,
low levels of control and the severity of its complications.
11-13
Despite the dearth of data and marked variation between and
within studies, hypertension is estimated to affect 10 to 30% of
Africans, virtually one in six people. In West Africa, hypertension
affects 30 to 40% of people aged 65 years or older in rural areas,
and approximately 50% of semi-urban dwellers. In the mixed
population (Coloureds) of South Africa, 50 to 60% of people over
the age of 65 years have hypertension. These figures approximate
the 60 to 70% prevalence of hypertension in African-Americans
over 65 years of age.
14
An estimated 75 to 80 million Africans,
more than twice the global estimate of people with HIV/AIDS, had
hypertension in 2000. The number of Africans with hypertension
will escalate to 150 million by 2025.
15