Cardiac screening examination of the fetus: guidelines for performing the 'basic' and 'extended basic' cardiac scan

Perinatal echocardiography: protocols for evaluating the fetal and neonatal heart

This Protocol for Evaluating the Fetal and Neonatal Heart details the indications, views, and measurements to be obtained for both (1) the basic screening examination of the fetal heart (a necessary component of all complete fetal anatomy evaluations) and the specialty study called (2) echocardiography as applied to either the fetus or neonate, using 2D and Doppler ultrasound. While the purpose of the screening study is to detect or exclude the possibility of a cardiac abnormality, echocardiography attempts to diagnose the specific anatomic and physiologic disruption. Also emphasized is the value of a collaborative team approach to management of the fetus and its parents when a cardiovascular anomaly is present, in an effort to achieve a smoother transition from fetus to neonate across the continuum of perinatal care.

Cardiac screening by STIC: can sonologists performing the 20-week anomaly scan pick up outflow tract abnormalities by scrolling the A-plane of STIC volumes?

OBJECTIVE

To assess whether medically qualified sonologists with low-to-intermediate scanning experience are able to detect major abnormalities of the outflow tracts by reviewing the A-plane of cardiac volume datasets acquired with spatiotemporal image correlation (STIC).

METHODS

Fourteen sonologists of low-to-intermediate scanning experience were recruited among residents and colleagues involved in the screening ultrasound clinic at our referral center. Basic criteria for selection were: ability to perform the 20-week anomaly scan and to assess the four-chamber view, inability to perform extended cardiac screening (outflows); willingness to participate in the study. These sonologists attended a 2-hour lesson on: a) how the outflow tract views can be abnormal, and b) how to use a laptop and the dedicated software to review cardiac volumes in the A-plane only. After this briefing, each of them, independently, reviewed 26 preselected volumes at a workstation (from 16 normal fetuses and 10 with outflow tract abnormalities), without knowing how many of them were normal. After reviewing each volume, the sonologist was asked to define the outflow tract views as normal or abnormal and, if willing, to hypothesize the anomaly. The sequence of cases was changed for each participant. The time allotted for review of the volumes was 1 hour (about 2 min per case).

RESULTS

Of the 364 diagnoses from review of the volumes, 116 (31.9%) were true positives, 195 (53.6%) were true negatives, 29 (8.0%) were false positives and 24 (6.6%) were false negatives. The sensitivity, specificity and positive and negative predictive values were 83%, 87%, 80% and 89%, respectively. Individual diagnostic accuracy ranged from 66 to 100% (median, 85.5%) and individual detection rate from 50 to 100% (median, 85%). The detection rate per single congenital heart disease ranged from 50% (for TGA with intact ventricular septum) to 100% (for DORV, DORV with pulmonary atresia and TGA with ventricular septal defect). There was no correlation between detection rate and alignment of the four-chamber view with the ultrasound beam (apical vs. transverse).

CONCLUSIONS

In this preliminary study, we have demonstrated that sonologists with low-to-intermediate experience of anomaly ultrasound screening in the second trimester and no experience of insonating the outflow tracts were able to identify outflow tract abnormalities by reviewing the A-plane of cardiac volume datasets, after detailed briefing.

Semi-automatic segmentation of fetal cardiac cavities: progress towards an automated fetal echocardiogram

OBJECTIVE

To develop a novel application of a tool for semi-automatic volume segmentation and adapt it for analysis of fetal cardiac cavities and vessels from heart volume datasets.

METHODS

We studied retrospectively virtual cardiac volume cycles obtained with spatiotemporal image correlation (STIC) from six fetuses with postnatally confirmed diagnoses: four with normal hearts between 19 and 29 completed gestational weeks, one with d-transposition of the great arteries and one with hypoplastic left heart syndrome. The volumes were analyzed offline using a commercially available segmentation algorithm designed for ovarian folliculometry. Using this software, individual 'cavities' in a static volume are selected and assigned individual colors in cross-sections and in 3D-rendered views, and their dimensions (diameters and volumes) can be calculated.

RESULTS

Individual segments of fetal cardiac cavities could be separated, adjacent segments merged and the resulting electronic casts studied in their spatial context. Volume measurements could also be performed. Exemplary images and interactive videoclips showing the segmented digital casts were generated.

CONCLUSION

The approach presented here is an important step towards an automated fetal volume echocardiogram. It has the potential both to help in obtaining a correct structural diagnosis, and to generate exemplary visual displays of cardiac anatomy in normal and structurally abnormal cases for consultation and teaching.

Potential pitfalls and methods of improving in utero diagnosis of transposition of the great arteries, including the baby bird's beak image

OBJECTIVE

The goal of this study was to analyze our recent experience with fetuses with transposition of the great arteries (TGA) to identify potential pitfalls and possible methods to better detect conotruncal anomalies such as TGA.

METHODS

We analyzed all nonreferral obstetric ultrasound examinations in which we performed basic, targeted, or formal fetal echocardiography with a newborn diagnosis of TGA.

RESULTS

Nine neonates had TGA. Five of these cases were diagnosed prenatally, and 4 of these had complex congenital heart abnormalities. In these 4 cases, there were abnormalities in the cardiac axis (n = 3), abnormal valves or ventricular size (n = 2), and ventricular septal defects (n = 3) that were detected on the 4-chamber view of the heart. In all cases that were not detected prenatally, both prospective and retrospective reviews of the 4-chamber heart appeared normal. The prospective analyses of the outflow tracts were all interpreted as normal, whereas the retrospective review showed subtle abnormalities such as the "baby bird's beak" image. In review of these cases, there was failure to show the "crisscross" relationship of the outflow tracts. In 1 case, 5 short axis views of the heart, retrospectively showed the artery originating from the left ventricle and bifurcated, representing the pulmonary artery.

CONCLUSIONS

Transposition of the great arteries may be associated with complex cardiac disease that could be detected on the 4-chamber view of the heart. When the 4-chamber view is normal, it is important to identify the crisscross relationship of the outflow tracts. If this is not done, it is important to document that the pulmonary artery bifurcates and originates from the right ventricle. Five short axis views of the heart may be helpful to detect conotruncal abnormalities.

The area behind the heart in the four-chamber view and the quest for congenital heart defects

OBJECTIVE

To evaluate the spectrum of fetal cardiac defects associated with abnormal sonographic findings in the area behind the heart (ABTH) in the four-chamber view.

METHODS

This study included a retrospective review of 393 fetuses with congenital heart defects (CHD) detected in 2003-2005 at our tertiary referral center and a prospective evaluation of 4666 fetal echocardiograms, including 220 cases of CHD, performed between January 2006 and February 2007. The retrospective and prospective groups did not differ significantly with respect to cardiac anomalies or abnormal findings in the ABTH, allowing us to combine the 613 fetuses with CHD investigated over a 50-month period.

RESULTS

In the study period, 69 fetuses had abnormalities of the ABTH (75% with major CHD). In 28 fetuses, two equally sized vessels ran behind the heart. Of these, 26 had an interrupted inferior vena cava with azygos continuation and two had total anomalous infracardiac pulmonary venous connection. In 41 fetuses, only one vessel was visualized, but the descending thoracic aorta was positioned contralateral to the cardiac apex. Of these, 29 had levocardia with right descending aorta. All of them had a right aortic arch. The remaining 12 had dextrocardia with left descending aorta.

CONCLUSIONS

The ABTH in the four-chamber view is easy to evaluate and offers important diagnostic markers for fetal CHD. Thus, it might enhance the screening performance of the four-chamber view. Attention must be paid to the number of vessels behind the heart and their laterality.

Pulmonary artery/aorta ratio in simple screening for fetal outflow tract abnormalities during the second trimester

OBJECTIVES

Congenital heart disease is associated with high mortality and morbidity rates, being the most life-threatening defect in the first month of postnatal life and accounting for approximately half of all childhood mortality from birth defects. Despite this, the prenatal detection rate for congenital outflow tract anomalies by ultrasound imaging is relatively low. The aim of this study was to establish a nomogram for the pulmonary artery/aorta (PA/AO) ratio measured in the three-vessel view plane. This ratio was investigated as a simple screening tool for congenital cardiac outflow tract abnormalities.

METHODS

The study was a prospective evaluation of 966 singleton fetuses at 16-24 weeks of gestation and 46 fetuses with congenital cardiac outflow tract abnormalities. The diameters of the pulmonary artery and aorta were measured in the three-vessel view. The PA/AO ratio was calculated and a nomogram was constructed. The mean and 95% CI for the ratio were defined and the PA/AO ratios of cases with outflow tract abnormalities were plotted against the values for normal fetuses.

RESULTS

The gestational age of the normal group ranged from 16 to 24 weeks, with a median of 19 weeks. The pulmonary artery diameter measured between 2.1 and 4.93 mm (mean, 3.3 mm) and the aorta measured between 2.1 and 5.2 mm (mean, 2.93 mm). The mean (SD) PA/AO ratio was 1.16 (0.18) (95% CI, 0.87-1.58; range 0.61-1.86; median, 1.14). For fetuses with outflow tract abnormalities, the median gestation was 19 weeks and 37/43 (86%) had a PA/AO ratio outside the 95% CI.

CONCLUSIONS

The PA/AO ratio derived from measurements in the three-vessel view plane can be used as an initial screening tool for outflow tract anomalies and may have a sensitivity of up to 86%, with a 5% false-positive rate.

3D and 4D ultrasound in fetal cardiac scanning: a new look at the fetal heart

Over the last decade we have been witness to a burgeoning literature on three-dimensional (3D) and four-dimensional (4D) ultrasound-based studies of the fetal cardiovascular system. Recent advances in the technology of 3D/4D ultrasound systems allow almost real-time 3D/4D fetal heart scans. It appears that 3D/4D ultrasound in fetal echocardiography may make a significant contribution to interdisciplinary management team consultation, health delivery systems, parental counseling, and professional training. Our aim is to review the state of the art in 3D/4D fetal echocardiography through the literature and index cases of normal and anomalous fetal hearts.

Right aortic arch detected in fetal life

OBJECTIVE

To evaluate the prenatal distribution, associated conditions and outcome of the different types of right aortic arch (RAA) detected in fetal life.

METHODS

This was a retrospective review of all cases of RAA detected prenatally between 1998 and 2005 in two tertiary referral centers.

RESULTS

In the study period 71 cases of RAA were detected; 26 (37%) had RAA with aberrant left subclavian artery, 23 (32%) had RAA with mirror-image branching, 20 (28%) had RAA of unknown type and two (3%) had double aortic arch. While 20/26 cases with RAA and aberrant left subclavian artery were isolated findings, all 23 cases with RAA and mirror-image branching were associated with cardiac defects, namely tetralogy of Fallot (43%) or pulmonary atresia with ventricular septal defect (22%). Of the 20 cases with RAA, 19 of unknown type were associated with heterotaxy syndromes and had additional cardiac malformations and ambiguities of the situs. The two cases with DAA were isolated findings. Seven cases in our series (10%) had a microdeletion 22q11 and these were significantly associated with extracardiac malformations. The outcome in our series depended solely on the associated cardiac and extracardiac malformations, with the exception of one infant with isolated DAA, in whom a surgical correction was warranted.

CONCLUSIONS

RAA detected in fetal life is associated frequently with other cardiac/non-cardiac malformations, heterotaxy syndromes and microdeletions 22q11. The associated conditions vary depending on the branching type of the brachiocephalic vessels and the presence of extracardiac malformations.

A novel algorithm for comprehensive fetal echocardiography using 4-dimensional ultrasonography and tomographic imaging

OBJECTIVE

Tomographic ultrasound imaging (TUI) is a new display modality that allows simultaneous visualization of up to 8 parallel anatomic planes. This study was designed to determine the role of a novel algorithm combining spatiotemporal image correlation and TUI to visualize standard fetal echocardiographic planes.

METHODS

Volume data sets from fetuses with and without congenital heart defects (CHDs) were examined with a novel algorithm that allows simultaneous visualization of the 3-vessel and trachea view, the 4-chamber view, and outflow tracts. Visualization rates for these planes as well as the ductal arch and 5-chamber view were calculated.

RESULTS

(1) Two hundred twenty-seven volume data sets from fetuses without (n = 138) and with (n = 14) CHDs were reviewed; (2) among fetuses without CHDs, the 4-chamber view, 5-chamber view, ductal arch, 3-vessel and trachea view, left outflow tract, and short axis of the aorta were visualized in 99% (193/195), 96.9% (189/195), 98.5% (192/195), 88.2% (172/195), 93.3% (182/195), and 87.2% (170/195) of the volume data sets, respectively; (3) these views were visualized in 85% (17/20), 80% (16/20), 65% (13/20), 55% (11/20), 55% (11/20), and 70% (14/20) of the volume data sets, respectively, from fetuses with CHDs; and (4) simultaneous visualization of the short axis of the aorta, 3-vessel and trachea view, left outflow tract, and 4-chamber view was obtained in 78% (152/195) of the volume data sets from fetuses without CHDs and in 40% (8/20) of those with CHDs.

CONCLUSIONS

The 3-vessel and trachea view, the 4-chamber view, and both outflow tracts can be simultaneously visualized using a novel algorithm combining spatiotemporal image correlation and TUI.