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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 4, July/August 2020
AFRICA
183
genetic ILVNC may manifest more commonly with the dilated
cardiomyopathy phenotype. However, no definitive conclusion
in this regard may be drawn until further work is conducted,
since to our knowledge no other screening studies have been
conducted in African families of subjects with ILVNC.
Echocardiography is the most commonly used technique
to diagnose ILVNC, as it is widely available, feasible and
non-invasive. However, echocardiography has several limitations,
which can lend itself to over- or under-diagnosis of ILVNC.
24,25
Echocardiography is highly dependent on the operator’s technical
skill to acquire suitable images and requires proper interpretation
of data received. There is also concern about the reproducibility
of current diagnostic criteria, which has demonstrated poor
inter-observer agreement.
26
Given these limitations, cardiac
magnetic resonance imaging (MRI) has a far superior spatial
resolution, less operator dependence and higher contrast in
the myocardium, which can provide better delineation of the
trabeculations.
A cohort study done by Diwardkar
et al
. showed how
echocardiography failed to detect ILVNC in patients diagnosed
with it on MRI.
24
In our study, cardiac MRI was not utilised,
and this may have improved the diagnosis of individuals
with ILVNC in subjects who were difficult to image or where
echocardiography missed the pathology.
One of the major findings of this study was that utilising
a strategy of clinical evaluation and ECG had a sensitivity
of 76% and a specificity of 42% versus the gold standard of
echocardiographic screening. In resource-deprived settings, such
a strategy may be attractive if it is used as the initial screening
strategy and followed by echocardiographic screening with or
without genetic screening. For such a strategy to be successful,
the initial screening strategy must ideally have a very high
sensitivity, which often implies a lesser degree of specificity.
Our findings highlight the failure of using the ECG in addition
to clinical evaluation as an initial screening strategy due to its
relatively modest sensitivity. Furthermore, the role of a 12-lead
ECG as a screening tool alone for ILVNC is debatable, as there
are no specific ECG patterns to diagnose ILVNC.
In a cohort study done by Steffel
et al
.,
27
the most common
findings on initial diagnosis of ILVNC were intraventricular
conduction delay, voltage signs of LVH and repolarisation
abnormalities. A completely normal ECG was present in only
13% of patients. These abnormal ECG signs can be found in
normal African individuals. Lohrmann
et al
.
28
showed that
early repolarisation patterns occurred in 53.2% of subjects.
LVH occurred in 13% and bundle branch blocks in 0.5% of
normal black adults with echocardiographically normal hearts.
Therefore using a strategy of clinical evaluation and an ECG
in this study was inferior since the sensitivity and specificity of
results were sub-optimal for screening.
Limitations of this study were that it was a retrospective
study with a small study population and therefore the external
validity of our secondary aim was limited. Not all eligible family
members were screened. Genetic testing and cardiac MRI were
not performed.
Conclusion
Echocardiographic screening detected DCMO in 10.8% of
subjects whereas no cases of ILVNC or HCM were identified. A
strategy of clinical screening that included electrocardiography
was sub-optimal as a screening strategy compared to
echocardiographic screening in this study.
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