Three- and four-dimensional ultrasound in fetal echocardiography: an up-to-date overview.

Congenital heart diseases (CHD) are the most commonly overlooked lesions in prenatal screening programs. Real-time two-dimensional ultrasound (2DUS) is the conventionally used tool for fetal echocardiography. Although continuous improvements in the hardware and post-processing software have resulted in a good image quality even in late first trimester, 2DUS still has its limitations. Four-dimensional ultrasound with spatiotemporal image correlation (STIC) is an automated volume acquisition, recording a single three-dimensional (3D) volume throughout a complete cardiac cycle, which results in a four-dimensional (4D) volume. STIC has the potential to increase the detection rate of CHD. The aim of this study is to provide a practical overview of the possibilities and (dis)advantages of STIC. A review of literature and evaluation of the current status and clinical value of 3D/4D ultrasound in prenatal screening and diagnosis of congenital heart disease are presented.

Prenatal examination of the area and morphology of the atrioventricular valves using four-dimensional ultrasound in normal and abnormal hearts.

OBJECTIVE: Our aim is to evaluate the feasibility to examine the morphology and area of the atrioventricular (AV) valves in normal fetuses and fetuses with cardiac defects using spatiotemporal image correlation (STIC). METHODS: Atrioventricular valves were analyzed longitudinally in STIC volumes of 74 normal fetuses between the 15th and 36th week of pregnancy. The valve area was measured in a rendered view in diastole, the number of valve leaflets in systole. Longitudinal data analysis was performed using linear mixed models. Fifty fetuses with cardiac defects were examined. RESULTS: Examination of 355 STIC volumes of normal fetuses showed in 82.5% sufficient quality. The tricuspid valve leaflets were seen in 200 (68.3%) volumes and the mitral valve leaflets in 219 (74.7%) volumes. The tricuspid valve showed in 61.1% a round, 29.0% rectangle, and 8.9% elliptical shape and the mitral valve in 60.1% round, 28.0% rectangle, and 10.9% elliptical. Regression analysis revealed a positive relationship of the valve area with gestational age (p < 0.0001). Most heart defects with stenosis showed an area below the 5th percentile. CONCLUSION: Prenatal examination of the morphology and area of the AV valves using four-dimensional ultrasound is feasible. A rectangular valve opening is normal, which was visualized in about one third of the normal fetuses.

Differential insertion of the atrioventricular valves: measurement protocol to detect various congenital heart defects.

OBJECTIVES: The objectives of this study were to develop reference values for the distance between the atrioventricular valves, called differential insertion of the atrioventricular valves (DIAVV), in normal fetuses using four-dimensional ultrasound with spatio-temporal image correlation and to explore if DIAVV measurement can differentiate between normal hearts and hearts with cardiac defects. METHODS: The DIAVV was analysed longitudinally following a measurement protocol in 74 fetuses between 15 and 36 weeks gestational age. The DIAVV was measured in an apical four-chamber view of the heart in end-diastole. Furthermore, the DIAVV was measured in 70 fetuses with cardiac defects. RESULTS: In total, 337 normal and 70 abnormal spatio-temporal image correlation volumes were examined. Longitudinal regression analysis revealed a positive relationship of the DIAVV with gestational age and fetal biometry (p < 0.0001). The DIAVV of fetuses with double outlet right ventricle, truncus arteriosus, atrioventricular septal defects, Ebstein and tetralogy of Fallot all differed from normal fetuses (p < 0.05). CONCLUSION: Measurement of the DIAVV is a promising tool; however, a well-defined measurement protocol should be followed to accomplish the correct plane and exact moment in the cardiac cycle. This study presents new nomograms following this measurement protocol and reports an abnormal DIAVV in a wide spectrum of congenital heart disease.

Differential and linear insertion of atrioventricular valves: a useful tool?

OBJECTIVE: The differential insertion of the atrioventricular valves is the ultrasonographic representation of the more apical attachment of the tricuspid valve to the septum with respect to the mitral valve. A linear insertion is present when both valves form a linear continuum and has been suggested as a marker for atrioventricular septal defects (AVSDs). The objective of this study was to evaluate the anatomical substratum of differential and linear insertions of the atrioventricular valves in normal fetal hearts and fetal hearts with an AVSD. METHODS: The extent and position of the fibrous skeleton and attachment of the atrioventricular valves to the septum were studied in histological sections of 17 normal hearts and four hearts with an AVSD from 10 + 0 weeks' gestation to 3 days postpartum with various immunohistochemical tissue markers. In addition, spatiotemporal image correlation (STIC) volumes of 10 normal hearts and STIC volumes of eight hearts with an AVSD at 13 + 6 to 35 + 5 weeks' gestation were examined. RESULTS: The differential insertion of the atrioventricular valves was visible in normal hearts in the four-chamber plane immediately beneath the aorta, but nearer the diaphragm a linear insertion was found. In hearts with an AVSD, a linear appearance was observed in the four-chamber plane immediately beneath the aorta. Towards the diaphragm, however, first a differential insertion and, more caudally, a linear insertion was found. CONCLUSIONS: Both differential and linear insertions can be found in normal fetal hearts and fetal hearts with AVSD, depending on the plane in which the four-chamber view is visualized. Therefore, measurement of the differential insertion is likely to be useful only in experienced hands.

Interobserver agreement in detailed prenatal diagnosis of congenital heart disease by telemedicine using four-dimensional ultrasound with spatiotemporal image correlation.

OBJECTIVE: To evaluate the clinical accuracy of four-dimensional (4D) echocardiography in the detailed prenatal diagnosis of congenital heart disease (CHD) in a telemedicine setting. METHODS: Ten second-trimester spatiotemporal image correlation (STIC) volumes were sent to three observers in different tertiary care centers with expertise in 4D echocardiography. The 10 volumes were selected based on the type of diagnosis to cover a wide spectrum of CHD anomalies, and also included one normal fetal heart. Observers were asked to provide the diagnosis, the postprocessing modalities used and the time spent on examination, and to give a rating of the confidence for the diagnosis on a 5-point Likert scale. They were free to consult other colleagues, including pediatric cardiologists, but were blinded to the prenatal diagnosis and the neonatal outcome. A diagnostic scoring system was used to evaluate different aspects of the heart defects. The results were compared with neonatal echocardiography or postmortem findings ('gold standard'). RESULTS: In two cases all observers correctly diagnosed all details of the volume datasets. The observer with the best performance reached perfect agreement in six cases and nearly perfect agreement in three. The volumes were most frequently studied by sectional planes and were analyzed in a median time of 11.0 (range, 2.5-30.0) min. The median confidence score was 4.0 (range, 1.0-5.0). CONCLUSIONS: In a telemedicine setting using STIC volumes, fetal cardiac anomalies can be diagnosed correctly by an expert. However, details required for adequate counseling and planning of postnatal care may be missed. STIC by telemedicine is a promising modality, although not accurate enough for exclusive use in clinical decision making regarding treatment, prognosis or termination of pregnancy.