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.