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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 25, No 6, November/December 2014
AFRICA
267
Discussion
The prevalence of CHD in this prospective, hospital-based study
of 14.4 per 1 000 is alarmingly higher than studies from other
parts of Nigeria, where it was 9.3,
8
and 4.6/1 000,
7
Egypt was
1.01,
10
India was 10.5,
11
the United State of America was 6.5,
12
Norway was 10.6,
13
and Austria was 6.9/1 000.
14
It is comparable
with other studies from Qatar where prevalence was 12.25,
15
and
Australia was 17.5/1 000.
16
This very high figure is most likely due to environmental
factors. Port Harcourt is in Rivers state in the Niger Delta
region, an oil-rich city in the south–south geographical zone of
Nigeria where crude oil exploration is rampant, and oil spillage
from petroleum exploration commonly affects water quality
and terrestrial fauna. Gas flaring constitutes a toxic threat to
inhabitants of these areas. Heavy hydrocarbons that cannot
be carried into the atmosphere fall back and become inhaled,
while others get attached to vegetables grown for consumption.
Over time, this may be toxic to the body or cause congenital
malformations in babies born in the area.
17
Toxic agents may
induce malformation in the foetus during the early weeks of
organogenesis.
As with other studies done in Nigeria and other parts of the
world, VSD was the commonest acyanotic CHD seen in this
study, with a frequency of almost half of the acyanotic CHD
(47. 3%); 39.5% of the CHD we saw was similar to that seen in
Saudi Arabia,
18
Mysore,
12
and Qatar.
15
The prevalence of VSD
was higher than previously reported in studies in Port Harcourt
Teaching Hospital, which was 34.1%,
9
30.3% in Kano,
8
32.3% in
the UK,
19
32.1% in the USA,
13
and 35.6% in Egypt,
10
but less than
the 55.3% reported in Benin.
7
TOF was the commonest cyanotic CHD, similar to studies in
Nigeria,
7-9
and worldwide.
10-16
That TGA ranks second may be due
to early mortality of the children. The two cases of dextrocardia
had rare presentations of situs solitus with no structural heart
defect,
20
dextrocardia, and situs inversus with multiple CHD.
21
Despite murmurs being the commonest indication for
requesting an echo, there are still many patients presenting late to
hospital, despite having been seen by numerous doctors managing
them for recurrent bronchopneumonia and tuberculosis. This is
due to the inability of attending junior medical staff to identify a
murmur on auscultation. This is further highlighted in this study
with only 9% of the patients reporting to hospital within the first
month of life.
Increased risks of structural birth defects and chromosomal
abnormalities have been reported to be due to air pollution
and proximity to environmental waste. The findings of a large
number of multiple congenital heart defects in these children is
worrisome and may be related to the teratogenic effect of gas and
oil spillage in the Niger Delta.
In this study, although no direct efforts were made to get
information about the place of residence of the parents, a
cursory review of the addresses showed that 28 (8.4%) of the
parents lived close to areas where gas is flared, nine (0.23%)
near telecommunication masts and 12 (0.04%) of the mothers,
when asked what routine antenatal drugs were ingested, had
mentioned a drug called Pregnacare. This contains multivitamins
as supplements, including omega-3, folic acid, iron and vitamin
B
12
.
These incidental findings have prompted an ongoing study
emphasing description of location and review of drugs ingested
by mothers of all children presenting with congenital heart
disease in our centres. Hypervitaminosis, potentially teratogenic
fumes and ionising radiation are being postulated as contributing
factors to this high prevalence of CHD.
It may be worth mentioning that six of the infants with
acyanotic heart disease were products of
in vitro
fertilisation
(IVF). All six had multiple CHD and were all of multiple
gestation. One patient, one of a set of triplets, had hypoplastic
left heart syndrome (HLHS) and died within one week of
diagnosis, at two weeks of life. The other siblings had structurally
normal hearts. Alhough not statistically proven in this study
as no comparison was made with children of parents who
conceived naturally, the high risk of CHD in IVF patients
has been previously documented.
22,23
This has also prompted
an ongoing prospective research on cardiac anomalies among
patients delivered by IVF in the Niger Delta area.
These results may be the tip of the iceberg, as few of these
cardiac patients present to hospital for diagnosis and fewer still
can afford the cost of an echocardiograph. Most of the patients
are still being managed by pharmacists and herbalists, mostly
due to poverty, ignorance and poor access to proper medical
care.
Conclusion
The high prevalence rate of CHD reported in this study area,
which has many environmental risks for CHD, is worrying. With
the increasing availability of echocardiography and paediatric
cardiologists in the region, and increased awareness, more cases
are likely to be detected in future. There is an urgent need to assess
and confirm the impact and causal relationship of oil spillage,
gas flaring, use of the drug Pregnacare, and residence close to
telecommunication masts in the Niger Delta, to make a genuine
case for the prevention and reduction in the prevalence of CHD
in this region. We emphasise the need to regulate the deleterious
activities of oil companies in the Niger Delta, and establish
cardiac centres in our country for cheaper and more easily
available diagnostic tools and early surgery to improve outcomes.
References
1.
Ferencz C, Rubin JD, Loffredo CA, Magee CA. Epidemiology of
congenital heart disease: The Baltimore–Washington Infant study
1981–1989. In: Anderson RH (ed).
Perspectives in Pediatric Cardiology
,
vol 4. Mount Kisco, NY: Futura Publishing, 1993: 353.
2.
Brickner ME, Hillis LD, Lange RA. Congenital heart disease in adults:
first of two parts.
New Engl J Med
2000;
342
: 256–263.
Table 4. Multiple CHD and frequency of occurrence
Type of CHD Number
% acyanotic CHD
(
n
= 277)
% total CHD
(
n
= 332)
VSD/PDA
53
19.1
16
VSD/ASD
6
2.2
1.8
ASD/PDA
16
5.8
4.8
ASD/VSD/PDA 12
4.3
3.6
ASD/PAPVC
2
0.7
0.6
AVCD/PDA
2
0.7
0.6
VSD, ventricular septal defect; PDA, patent ductus arteriosus; ASD,
atrial septal defect; PAPVC, partial anomalous pulmonary venous
connection; AVCD, atrio-ventricular canal defect.