Discussion
The operators appear to have systematically included LVOT images in
their screening practices, as images of the LVOT were found in 95% of
the files studied. With regards to image quality, practices have
improved since 2017, but there was no difference over the study period
(first quarter of 2020) since the introduction of the quality criteria.
Practitioners who were already aware of the use of LVOT images before
the new recommendations continued to use them systematically, and
probably more accurately after 2016. Scores were not significantly
higher in the second trimester relative to the third trimester. Given
the results of the Var center, echocardiography screening activity in
the primary center is just as satisfactory as in the tertiary center.
The scores obtained according to cardiac position show a significant
improvement in average scores for Positions 2 and 3 when the back of the
foetus is in the posterior position between 3 and 9 o’clock. It was
noted that the Quality Criteria 5, 6 and 7 were very poorly considered
over the three periods, regardless of cardiac position.
In addition to obtaining the required images, it is relevant to carry
out a “quality” screening examination. This notion of quality
presupposes that the images obtained are as informative as possible. As
early as 2003, Chaoui advocated quality control of foetal
echocardiograms in order to avoid inadequate examinations (7).
Certification, similar to that required for first-trimester assessments,
could be considered in an attempt to improve screening. Indeed, in some
countries, regular audits for maintaining certification or quality
control have been successful (12)(13)(14). Since then, the notion of
quality control and auditing has developed in the field of
echocardiography, with first-trimester cardiac screening examinations in
low-risk populations (15), as well as cardio-thoracic ratio measurement
(16), the use of four-chamber views (17)(18) and the outflow tracts
(17)(19). With regards to the 4-chamber view, apical or basal views are
recommended in order to respect the quality criteria proposed(18).
However, to a lesser extent, side views are also recommended. For the
LVOT, one of the most important criteria is visualization of the
interventricular septum and, in particular, its relationship to the
possible overlying vessel. This area of interest is best visualized in
2D, when the ultrasound beam approaches it perpendicularly and not, as
is too often the case, by taking a perpendicular approach to the lower
part of the interventricular septum (Figure 11 ), with the risk
of misinterpreting interventricular communication of the conical region,
as shown by our example in Figures 12 and 13 . This principle of
taking a perpendicular approach to the anatomical region on either side
of the aortic valves is fundamental, whether the approach is anterior or
posterior. It is therefore preferable to use a lateral approach to the
LVOT. This underlines the importance of a dynamic examination by means
of scanning and angulation methods for probes producing the ultrasound
beam (5)(11)(20) and this point was also already highlighted by Sklansky
and De Vore (8) .
The detection of conotruncal anomalies should and could be improved
(21). This leads us to question the causes of such errors during
ultrasound screening. Several factors, unrelated to the operator, have
already been highlighted by different teams: gestational age at the time
of ultrasound, maternal adipose tissue, history of abdominal surgery,
foetal position, quantity of amniotic fluid, position of the placenta,etc. (22)(23). Other limiting factors directly attributable to
sonographers have also been demonstrated: the experience of the operator
(23), the number of ultrasound scans carried out annually, the inability
to obtain the required images or so-called “quality” images and the
inability of the operator to recognize unusual images despite obtaining
quality anatomical images. The latter concepts have again been reported
recently by Sun et al. (24) and Van Nisselrooij et al.(9), who also confirm that the main current limitation of CHD screening
is linked to in poor image quality for other outflow tracts.
In the light of these observations and the relative consistency in
reported CHD screening, it would appear to be appropriate to accept the
extent of training programmes for sonographers, however, it is essential
to propose solutions which should accompany these programmes. It is with
this in mind that Artificial Intelligence (AI) has been developed.
Currently, the most relevant model in automated learning of image
analysis is the convolutional neural network (25)(26). AI could thus
help the practitioner by carrying out a real-time audit of the images
provided (presence or absence and quality), helping to obtain
recommended quality anatomical images (27), but also in terms of
improving image resolution (28)(29)(30). AI could thus be of great help,
not from a diagnostic perspective, but rather as a support tool for the
practitioner and a guarantee of quality, analogous to a seatbelt in a
car, as it may be associated with a potentially high negative predictive
value regarding the risk of major CHD.
The strengths of our study
. This was a multicenter study based in different centers with
practitioners from different backgrounds and with different levels of
experience, providing an example of current screening practices in the
same country in tertiary and primary centers.
. This work focused on the quality of echocardiographic screening and
the causes associated with the current limitations of screening for CHD.
. Inter- and intra-operator variability regarding the proposed criteria
was low, as the kappa coefficients were all reported at between 0.601
and 1. Concordance ranged from good to very good, thus the scoring of
the images was carried out correctly and the proposed criteria were easy
to use.
. The evaluation of the quality criteria proposed was carried out in
routine practice by operators who probably have different degrees of
motivation in their desire to use new tools aimed at improving screening
practices. Indeed, most of the studies relating to the study of quality
criteria were carried out in tertiary centers with operators working in
close contact with the person(s) capable of ascertaining the quality
criteria. We thus acknowledge that the reality may be quite different,
and this sheds new light on what underlies the current limitations of
CHD screening.
. Quality criteria for LVOT screening should be distinguished from
normality criteria. For example, for Criterion 6, the quality criterion
is not the presence of septo-aortic continuity but the visualization of
the relationship between the interventricular septum and the possible
overlying vessel, whether or not there is continuity between the
interventricular septum and this possible vessel.
Limitations of the
study
. It is not possible to know whether the lack of images in the files
reflects a lack of investigation of the area in question, or whether the
area was investigated but no image was available and stored to
demonstrate this.
. Does a significant difference in quality score truly reflect a lack
of, or a real change in practice, with a real clinical impact? Indeed,
assessment of the only relevant difference would be based on rates of
detection of heart defects recorded in registers.
. The lack of significant improvement in scores after the introduction
of the quality criteria raises questions about their relevance and use,
but also about the techniques associated with guidance on how to
implement them. Practitioners may have been made aware of the
contribution of the quality criteria even if this was not reflected in
the analysis. It is clear that we should try to understand the causes
behind the non-compliance of these criteria: difficulty in understanding
them, in remembering to use them and/or being aware of them.