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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 5, September/October 2020
AFRICA
225
The prevalence of congenital heart disease: we need to
work towards getting more data
John Lawrenson
In 2020, 80% of children with congenital heart disease will
survive into adulthood if the abnormality is recognised early
and the child is offered appropriate surgery or intervention. Due
to many competing health needs, there are many barriers to
obtaining effective treatment in many parts of the world. One of
the barriers is poor recognition of disease. It is therefore essential
that the contribution of congenital heart disease to the burden of
disease in a given area is well documented.
In this issue (page 257), Mazhani and colleagues describe
the patients seen with congenital heart disease at the major
referring hospital in Botswana over a two-year period, starting
in January 2010.
1
By using a second, shorter time period in 2014
as a comparator, the authors estimated that the prevalence of
congenital heart disease in Botswana is between 2.8 and 4.95 per
1 000 live births.
Determining the incidence and prevalence of congenital heart
disease offers the epidemiologist a unique set of challenges. The
diagnosis of ‘a gross structural abnormality of the heart or
intrathoracic great vessels’
2
is not only dependent on the tools
used to define the abnormality but also on mode of presentation.
In most instances, the best tool to describe the occurrence of new
cases of children with congenital heart disease is actually the
prevalence of congenital heart disease in children from birth to
one year of age rather than the incidence at birth.
3
The authors of the most recent publication of the Global
Burden of Disease collective on congenital heart disease
4
estimate
that the global birth prevalence of congenital heart disease is
18/1 000 live births; the prevalence in southern sub-Saharan
Africa is around 20/1 000 live births.
A systematic review including 260 publications published in
2019
5
concluded that the global birth prevalence of congenital
heart disease was 9.410/1 000 live births at the end of 2017. The
authors of this article and those of a systematic review from
2010
6
pointed out that data from Africa are poor.
The difference between the global burden of disease data and
the systematic review is probably related to the methodology
used by the global burden of disease group where multiple tools,
including sophisticated mathematical modelling, are used to
make up for the lack of ‘conventional’ data.
4
Why is it important to obtain accurate data on
congenital heart disease in Africa?
Julien Hoffman, the leading epidemiologist who died in June
2020, published a ‘thought experiment’ in this journal in 2013,
7
where he pointed out that if a figure of 8/1 000 is applied to the
younger and more fertile population of Africa, about 335 000
children with congenital heart disease would be born every year
in Africa out of a total of 1.3 million children worldwide.
The infant and under-five mortality data of a country could
generally be considered to be effective markers for the social
determinants of health of that community. As socio-economic
conditions improve, fewer children will die from infectious
diseases.
4
In many countries in Europe, for example, congenital
heart disease is the leading cause of under-one-year mortality
after deaths resulting from premature birth.
4
As socio-economic conditions improve in our part of the
world, more children with congenital heart disease should be
recognised. Currently it is possible that many children with
severe (yet potentially treatable) congenital heart disease die and
their deaths are ascribed to septicaemia or respiratory disease. As
access to cardiac surgery improves in a country, the value of early
diagnosis of treatable disease becomes obvious. In addition,
survivors with untreated congenital heart disease become adults
who are chronically ill.
8
Why are good data so hard to obtain?
As a result of improvements in echocardiography, the recog-
nition of congenital heart disease has improved, and the
prevalence figures have tripled since the 1950s.
6
The majority
of children with congenital heart disease (> 65%) do not have
other phenotypic abnormalities.
9
Determining the presence of
congenital heart disease at birth in all
children would therefore
depend on routine, high-quality foetal ultrasound examination
or post-natal echocardiography in all children, not only children
with obvious genetic abnormalities.
The best estimate of the birth prevalence of congenital heart
disease in a given community would require the performance of
a prospective study involving many thousands of participants.
About a third of children (3–4/1 000 live births) with congenital
heart disease have severe disease and will most likely die from
the condition in the first year of life if left untreated. Therefore,
small prevalence studies (such as the study of Mahzani
et al
. in
this issue)
1
with a median population age of 1.3 years are likely
to miss critically ill patients who have died. In addition, as noted
by the authors, children referred for evaluation in this study
were symptomatic; children with large atrial septal defects for
example, may not have been seen.
Paediatric Cardiology Service of the Western Cape;
Department of Paediatrics and Child Health, Stellenbosch
University; Red Cross War Memorial Childrens’ and
Tygerberg Hospitals, Cape Town, South Africa
John Lawrenson, MB BCh, FCP (SA), MMed (Int),
john.lawrenson@uct.ac.zaEditorial