Summary
The information gained is dependent on the
examiners image optimization and scanning skills, the examiners
knowledge of cardiac anatomy and anomalies,
and the spatial imagination of the interpreting physician.
In a recent nationwide, population-based study, increased accuracy and
prenatal detection rates of major CHDs have led to an increase in
terminated pregnancies and subsequently decreased live-birth incidence
of fetuses with major CHDs81,82. These findings have
been confirmed by other groups83,84, emphasizing that
vigilant care should be placed on cardiac evaluation when termination is
considered due to a cardiac anomaly. The question of if prenatal
diagnosis effectively improves population health has been addressed by a
number of publications to date. Antenatal detection of a treatable
critical congenital heart disease was associated with lower morbidity
and mortality85. In this regard, as data from the
EPICARD study imply, postnatal survival may no longer be the most
relevant outcome criterion for evaluating the impact of a prenatal
diagnosis of a CHD. Indeed, as recent studies have shown, prenatal
diagnosis can improve the neurodevelopmental outcomes of newborns with
CHDs (e.g., TGA)86,87. Thakur and colleagues
demonstrated that a prenatal diagnosis of a critical CHD in their study
was associated with a significantly shorter time interval from birth to
neonatal admission and the absence of life-threatening or fatal
preoperative cardiac events88. Even in aneuploidy
syndromes, timely prenatal diagnosis of CHDs and appropriate follow-up
into adulthood have been shown to improve outcomes in these complex and
multisystem conditions89.
However, acknowledging that antenatal identification of a number of
severe cardiac anomalies is good and merely straightforward, the
detection rates of CHDs in general have remained low. The most commonly
missed severe CHDs are conotruncal lesions, such as transposition of the
great arteries, tetralogy of Fallot, double outlet right ventricle or
truncus arteriosus, since the four-chamber view may be falsely
reassuring in the majority of these cases90. The
addition of more standard views has been shown to increase the detection
rate of CHDs, as this increase may yield valuable information on most
left and right-sided cardiac lesions and is cost effective according to
recent data91,92.
According to the results from a very recent national survey of
physicians, the main barriers preventing effective cardiac screening
were knowledge of CHD screening guidelines and minimal volumes of
cardiac scans93. Detailed characterization of fetal
cardiac function in normal and abnormal fetal hearts is feasible and
well described using conventional 2D ultrasound. Functional assessment
of the fetal heart applying volume data sets has been shown to provide
reliable information on cardiac integrity irrespective of the fetal
position in utero . Volume measurement using 4DUS allows for
virtual organ computer-aided analysis (VOCAL) to estimate the
ventricular volume and calculate the total systolic volume, ejection
fraction, and cardiac output94,95;
SonoAVC96 or M-STIC can be used to calculate the AV
valve annular plane systolic excursion
(MAPSE/TAPSE)97. These imaging modalities are
applicable for different (patho)physiological fetal conditions (e.g.,
normal fetuses, fetuses with cardiac anomalies, growth restricted
fetuses or diabetic pregnancies)98-101. However, as
aforementioned, the continuing challenge is primarily the capability of
morphologic assessment rather than the description of functional and
quantitative changes in cases suspicious for congenital heart disease.
There is a general consensus that high-quality STIC volume data sets are
informative and potentially able to effectively address this issue. The
introduction of electronic spatiotemporal image correlation (eSTIC)
reportedly improved four-dimensional fetal echocardiography in terms of
acquisition time and image quality102. Depiction of
multiple parallel cut sections from the same image planes, as
exemplified by tomographic ultrasound imaging (TUI), might be of help in
illustrating spacious derangement in certain cases suspicious for
CHDs103, but it fails to display differently
orientated diagnostic planes, as shown by fetal echocardiography
guidelines. The method reviewed herein automatically reconstructs all
nine standard fetal echocardiography views required to diagnose most
cardiac abnormalities, as illustrated above. Recently introduced novel
and advanced features of FINE including very rapid static volume
acquisition (i.e., 1 second), characterized by a high frame rate or the
ability to precisely manipulate a single cardiac plane (volume) along
the x, y, or z plane or perform parallel shifts by applying monoplanar
navigation have been shown to ease cardiac
volumetry21.
Taken together, combining the details of (ab)normal cardiac morphology
using standardized approaches (FINE technology) with functional
parameters to quantify subtle changes (cardiac remodeling) retrieved
from a single STIC volume will prospectively contribute to improved
prenatal detection and surveillance of fetuses with CHDs and other
stressing conditions in utero . This underscores the indispensable
need for adequate training of operators to effectively and reproducibly
deploy the benefits of cardiac volumetry.