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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 5, September/October 2020
260
AFRICA
VSD was the most common acyanotic lesion. In descending
order of prevalence, other common acyanotic lesions were
PDA, AVSD, pulmonary stenosis (PS), PDA in combination
with a VSD, and atrial septal defect (ASD). TOF was the most
common cyanotic lesion followed by truncus arteriosus (TA).
The majority of African countries report VSD, TOF and PS
as the most common lesions. A summary of the most prevalent
CHD lesions by country is as follows: VSD and TOF in Cameroon
and Nigeria,
3,5
VSD, PS and ASD in Egypt,
6
VSD, TOF and PDA
in Zimbabwe,
7
VSD, TOF, PS, PDA, AVSD and ASD in Sudan,
8
and VSD, TOF and PS in Mauritania.
9
Worldwide the prevalence
of CHD types in descending order of prevalence is VSD, ASD,
PDA, PS, TOF, co-arctation of the aorta (CoA), transposition of
the great arteries (TGA) and aortic stenosis (AS).
4
VSD is the most common CHD lesion found in both
African and Western countries.
10
In the 46% of patients where
VSD type was recorded, muscular and membranous VSDs
were most common in Botswana. Globally, peri-membranous
VSDs are most common (70%).
11
Outlet (infundibular or conal)
defects account for 5–7% of VSDs in Western countries, but
can be as high as 30% in far Eastern countries.
11
Globally, inlet
(or atrioventricular canal) defects account for 5–8%, while
trabecular (muscular) VSDs account for 5–20% of VSDs.
11
The fact that ASD did not appear as the second or third most
common congenital heart disease actually underlines the most
important bias associated with hospital-based studies. Because
ASD is mostly asymptomatic in childhood and its murmur is
also a soft pulmonic ejection murmur (flow murmur), it is the
most common CHD diagnosed in adults for the first time. Silent
PDAs (PDA
<
1.5 mm, no murmur) may also not present to
medical attention. Therefore, sampling a group of newborns or
children from different communities based on certain attributes
and carrying out echocardiography would be a reliable way of
calculating the prevalence.
AVSD was the third most common lesion in our study. It was
the fifth most common lesion in a Sudanese study
8
but was not
found to be very prevalent in most other African studies. In a
meta-analysis of worldwide CHD, articles studying only specific
groups such as trisomy 21 were excluded. Eighteen patients in
our study were found to have trisomy 21 and 10 (56%) had an
AVSD. This may explain why our cohort was relatively ‘enriched’
for AVSD patients compared to these other studies.
TOF was the fourth most common CHD lesion, and the
most common cyanotic lesion. In most African countries such
as Cameroon, Nigeria, Zimbabwe, Sudan and Mauritania, TOF
was the second most prevalent lesion and the most common
cyanotic lesion.
5,7-9,12,13
We report an older age of patients with
TOF in our study with a mean age of 6.1 years, however this
likely reflects a survivor effect as patients with TOF in Botswana
are referred for corrective cardiac surgery.
A small proportion of patients had acquired cardiac lesions.
These included cardiomyopathy, pericardial effusion, cor
pulmonale, rheumatic heart disease (RHD) and malignancy,
in descending order of prevalence. As anticipated, the median
age of CHD (0.9 years) was significantly lower than that of
acquired heart disease (3.2 years). Nearly a third of children
with pericardial effusions were underweight, likely in keeping
with having tuberculosis, which accounts for the majority of
pericardial effusions in Botswana. Only seven patients had RHD,
suggesting a low prevalence of this condition. Similarly, Cilliers
in neighbouring South Africa has reported a marked decline over
the past two decades in the incidence of children with both acute
rheumatic fever and RHD.
14
We assume that the low prevalence
of RHD was due to an improvement in the socio-economic
circumstances in Botswana, including ready access to first-line
antibiotics, as has been the case globally.
When recorded, the most common indication for requesting
echocardiography was presence of a risk factor for CHD.
The most common recorded risk factor was trisomy 21. By
comparison, in the Niger Delta region of Nigeria, a murmur was
the most common indication for an echocardiograph.
15
In our study, there was a skewed distribution of ages, with
most subjects being young and a few being older. This resulted in
a non-normal age distribution for the study cohort; the median
age for the total study group was 1.3 years (interquartile range
0.2–5.4). Close to one-third (27%) of the entire study population
was less than three months of age.
In most longitudinal series of CHD, approximately two to
three per 1 000 newborns with CHD will be symptomatic in
the first year of life. By one week of life, the diagnosis is often
established in 40–50% of patients, while the diagnosis will be
established in 50–60% of patients by one month of life.
5
The mean age of patients with CHDwas 2.8 years in our study,
which may suggest a slightly delayed age of diagnosis. However,
it was a challenge in our cohort to accurately determine the
precise age of first presentation for most patients, because most
had had previous echocardiographs prior to the study period. In
patients who had had multiple echocardiographs, the report for
the first echocardiograph was chosen.
The majority of patients with acquired lesions were older
than five years, as anticipated. We therefore expect that the
mean and median ages of CHD patients reported in our study,
although correct for our study cohort, are in fact higher than
would be found in a prospective cohort study where the age
of first echocardiogram and therefore first diagnosis of CHD
would be lower, and likely more similar to the younger ages
reported in the literature. This speaks to the need for future
prospective cohort studies.
Limited antenatal screening for CHD in Africa has led to the
majority of congenital cardiac lesions being diagnosed postnatally.
The onset of permanent sequelae can be prevented by early
diagnosis of simple cardiac lesions, but this remains a challenge in
Africa.
16
In Malawi the age of presentation for both congenital and
acquired heart disease was late.
17
The mean age of presentation for a
VSD was 3.2 years, while for RHD it was 11.5 years. Consequently
a large number of patients with left-to-right shunts had pulmonary
hypertension at the time of diagnosis.
17
Studies from both Nigeria
and Cameroon also found patients who presented late with
Eisenmenger complex and shunt reversal.
5,12
In our study only one
patient was found to have Eisenmenger complex.
There were no significant gender differences in our study
population. In India however Sawant
et al.
found a male
predominance of CHD, which was similar to two other studies
in India with similar findings.
18
The estimated national prevalence of CHD in the study group
was 2.8 per 1 000 live births. This was an underestimate due to
the limitations of our study design that entailed capturing data
from only one of two paediatric cardiologists during the study
period; hence the need for the comparator group. The estimated
national prevalence of CHD as estimated from the comparator