Single umbilical artery and congenital heart disease in selected and unselected populations

OBJECTIVE

A variable association between single umbilical artery (SUA) and congenital heart disease (CHD) has been reported previously. Discrepancies in the results may be related to the populations studied. In this study we assessed the relationship between SUA and CHD in two well-defined selected and unselected populations.

METHODS

This was a retrospective review of all cases of SUA detected antenatally in a tertiary referral center between 1997 and 2003. Umbilical arteries were routinely identified around the fetal bladder by color-flow Doppler ultrasonography. The unselected population included pregnancies from a well-defined geographical area, delivering in the same hospital. The selected group was referred from other hospitals because of suspected abnormalities or other risk factors. Major CHD was defined as CHD needing postnatal treatment or long-term follow-up.

RESULTS

There were 10 fetuses with major CHD in the selected group: four cases among 25 with extracardiac defects (16%; 95% CI, 4.5-36.1%) and six cases out of 22 with no other abnormalities (27%; 95% CI, 10.7-50.2%; P = 0.35). In the unselected group there were two cases of major CHD, both among the 13 fetuses with extracardiac abnormalities (15%; 95% CI, 2-45%), while there were no major cardiac defects in the 85 fetuses with SUA and no extracardiac abnormalities (0%; 95% CI, 0-4%; P = 0.03).

CONCLUSIONS

The association between SUA and CHD varies dramatically with population selection criteria. The risk for CHD after the detection of SUA in an otherwise apparently normal fetus from an unselected population seems small and may not warrant specialist fetal echocardiography.

Prenatal findings and differential diagnosis of scimitar syndrome and pulmonary sequestration

OBJECTIVES

Scimitar syndrome and pulmonary sequestration (PS) have overlapping features. This accounts for postnatal descriptions of a 'sequestrated lung' in scimitar-syndrome patients. We review the similarities and differences in these two conditions, and the antenatal ultrasound findings that allow correct prenatal identification and differential diagnosis.

METHODS

This was a retrospective analysis of prenatally diagnosed cases of scimitar syndrome or PS that underwent fetal echocardiography between January 1995 and November 2004.

RESULTS

There were five cases of PS and six of scimitar syndrome. Right-sided mediastinal shift (ipsilateral relative to the affected lung) was the commonest indication for referral in scimitar syndrome whereas in sequestration, referral was because of hyperechogenic lung and contralateral mediastinal shift. Lung echogenicity was normal in scimitar syndrome but focally increased in PS. Abnormal, unobstructed pulmonary venous drainage was identified prenatally in four cases of scimitar syndrome. It was normal in three fetuses with sequestration but abnormal and obstructed in the other two cases complicated by hydrothorax. Abnormal systemic arterial supply to the affected lung was easily demonstrated in all fetuses with PS, but could not be shown prenatally in scimitar-syndrome fetuses. Postnatal embolization was warranted in one case with PS and four with scimitar syndrome, one each in the neonatal period.

CONCLUSION

Prenatally, scimitar syndrome and PS are clearly distinct entities based on lung echogenicity and laterality of mediastinal shift. Hyperechogenic lung and dextrocardia indicate the possibility of PS and scimitar syndrome, respectively. Complete delineation of the vascular pattern should be attempted in all, but is more challenging in scimitar syndrome. Obstructed venous return in PS may identify fetuses at risk of developing hydrothorax.

Impact of audit of routine second-trimester cardiac images using a novel image-scoring method

OBJECTIVE

To assess the impact of using an objective scoring method to audit cardiac images obtained as part of the routine 21-23-week anomaly scan.

METHODS

A prospective audit and re-audit (6 months later) were conducted on cardiac images obtained by sonographers during the routine anomaly scan. A new image-scoring method was devised based on expected features in the four-chamber and outflow tract views. For each patient, scores were awarded for documentation and quality of individual views. These were called 'Documentation Scores' and 'View Scores' and were added to give a 'Patient Score' which represented the quality of screening provided by the sonographer for that particular patient (maximum score, 15). In order to assess the overall performance of sonographers, an 'Audit Score' was calculated for each by averaging his or her Patient Scores. In addition, to assess each sonographer's performance in relation to particular aspects of the various views, each was given their own 'Sonographer View Scores', derived from image documentation and details of four-chamber view (magnification, valve offset and septum) and left and right outflow tract views. All images were scored by two reviewers, jointly in the primary audit and independently in the re-audit. The scores from primary and re-audit were compared to assess the impact of feedback from the primary audit.

RESULTS

Eight sonographers participated in the study. The median Audit Score increased significantly (P < 0.01), from 10.8 (range, 9.8-12.4) in the primary audit to 12.4 (range, 10.4-13.6) in the re-audit. Scores allocated by the two reviewers in the re-audit were not significantly different (P = 0.08).

CONCLUSION

Objective scoring of fetal heart images is feasible and has a positive impact on the quality of cardiac images acquired at the time of the routine anomaly scan. This audit tool has the potential to be applied in every obstetric scanning unit and may improve the effectiveness of screening for congenital heart defects.

Criss-cross heart: report of three cases with double-inlet ventricles diagnosed in utero

Criss-cross heart is a rare congenital cardiac anomaly characterized by crossing of the inflow streams of the two ventricles, due to an apparent twisting of the heart about its long axis and when the axes of the openings of the atrioventricular (AV) valves are not parallel. If unrecognized, this leads to incorrect sequential segmental analysis. We report three cases of double-inlet ventricle with a criss-cross spatial relationship of the AV valves detected on prenatal ultrasound examination at 19-23 weeks' gestation. The sequential diagnosis was confirmed at postmortem examination in two cases and by neonatal echocardiography in the other. Antenatal diagnosis of criss-cross effect of the AV valves is feasible, allowing correct fetal diagnosis and appropriate counseling for this rare form of congenital cardiac disease.

Assessment of the intraobserver variability in the measurement of fetal cardiothoracic ratio using ellipse and diameter methods

OBJECTIVE

To assess the variability of fetal heart and thoracic area and circumference measurements using the ellipse and diameter methods at different gestational ages.

DESIGN

This was a prospective cross-sectional study of 200 singleton pregnancies, with no apparent fetal abnormalities. The gestational age ranged between 19 and 42 weeks. At each examination, two transverse frames of the fetal chest at the level of the four-chamber view during diastole were obtained. For each frame, the area and the circumference of the heart and thorax were obtained by the ellipse and diameter methods. In the diameter method, cardiac and thoracic areas and circumferences were derived from the measured anteroposterior and transverse diameters. All measurements were made by the same observer.

RESULTS

For the same method, intraobserver variability was good. Coefficient of variation for all measurements varied between 3-11%. The ellipse method tended to give larger measurements than did the diameter method, the absolute difference increasing with fetal age. The mean ellipse/diameter ratio was 1.10, 1.04, 1.05 and 1.02 for heart area, thorax area, heart circumference and thorax circumference, respectively. In most cases, intraobserver variability of the thorax measurements was independent of gestational age. In contrast, there was a greater variability of heart measurements with increasing gestational age.

CONCLUSIONS

Both the ellipse and diameter methods of measuring cardiothoracic ratio are clinically useful and fairly reproducible at certain gestations, but are not interchangeable as the ellipse method overestimates measurements compared to the diameter method. The less reproducible measurement of heart size in later gestation should be taken into account when assessing cardiothoracic ratios.

Development of Z-scores for fetal cardiac dimensions from echocardiography

OBJECTIVES

Z-scores for cardiac dimensions are well established in postnatal life, but have yet to be developed for fetal cardiac dimensions. These would be of real advantage to the clinician in accurately quantifying size and growth of cardiac dimensions and to the researcher by allowing mathematical comparison of growth in differing subgroups of a disease. The purpose of this observational study, conducted at tertiary fetal medicine and cardiology units, was to produce formulae and nomograms allowing computation of Z-scores for fetal cardiac dimensions from knowledge of femur length (FL), biparietal diameter (BPD) or gestational age (GA) using fetal echocardiography.

METHODS

Seventeen fetal cardiac dimensions were measured in 130 pregnant women with singleton fetuses of gestational age 15-39 weeks. Regression equations were derived relating all dimensions to FL, BPD and GA. From the calculations, formulae were then developed allowing fetal cardiac Z-score computation.

RESULTS

The relationships between cardiac dimensions and FL, BPD or GA were described following natural log transformation. From this analysis, FL (taken as an expression of fetal size) had the highest correlation to fetal cardiac dimensions. From the developed nomograms, Z-scores of specific fetal cardiac structures could be estimated from knowledge of the FL, BPD or GA and echocardiographically derived measurements.

CONCLUSIONS

This study allowed computation of Z-scores in fetal life for 17 cardiac dimensions from FL, BPD or GA. Previous studies of normal data allowed qualitative assessment of where abnormal cardiac dimensions lay with regard to the normal range. Z-scores from this study allow quantitative analysis of where such dimensions lie relative to the mean. This permits exact assessment of growth of fetal cardiac structures in normal hearts and particularly in congenitally abnormal hearts where quantitative assessment of the growth of cardiac structures is important in analyzing and planning treatment strategies.

Increased first-trimester fetal nuchal translucency thickness in association with chondroectodermal dysplasia (Ellis-Van Creveld syndrome)

Increased nuchal translucency thickness (NT) is an established sonographic marker of fetal chromosomal abnormality. Several structural fetal defects and genetic syndromes including a range of skeletal dysplasias have been reported in association with increased NT. We report the first case of fetal Ellis-Van Creveld syndrome presenting as raised fetal NT at 13 weeks' gestation. Ultrasonography at 18 weeks' gestation demonstrated a narrow thorax, marked shortening of the long bones with bowed femora and hexadactyly of hands and feet. Pregnancy was terminated at 23 weeks' gestation. The postmortem radiological examination revealed short and bowed long bones with rounded metaphyses, postaxial polydactyly of hands and feet, short ribs and narrow thorax. The acetabular roofs were horizontal with medial and lateral spurs. This case adds a further type of severe skeletal dysplasia to the list of genetic syndromes which may present as increased fetal NT in the late first trimester.

Fetal congenital cardiac diverticulum with pericardial effusion: two cases with different presentations in the first trimester of pregnancy

Two cases of fetal congenital cardiac diverticula diagnosed at 14 and 12 weeks of gestation are reported. Both presented with a large pericardial effusion. One fetus presented with increased NT which evolved into fetal hydrops. Pericardiocentesis at 16 weeks led to progressive resolution of hydrops. The other showed no hemodynamic compromise, normal nuchal translucency (NT) and spontaneous regression of the effusion. Both children were well at 22 and 17 months of age at the time of writing.

Fetal echocardiography. A sophisticated tool in obstetrics

Fetal cardiology has been evolving as an exciting speciality over the last 20 years or so. Whilst much is due to technical advances in fetal echocardiographic techniques and the use of sophisticated ultrasound equipment, the partnership among fetal and paediatric cardiologists and a team of professionals working in Fetal Medicine Unit should not be ignored. As a result, targeted fetal echocardiography allows congenital heart disease to be diagnosed in utero with a great degree of accuracy from as early as the end of the first trimester of pregnancy i.e. from around 12 weeks. Conversely, prenatal detection rates in the general population remain suboptimal with many congenital cardiac abnormalities being diagnosed postnatally. A recognised marker for chromosomal abnormalities, that is the finding of an increased nuchal translucency thickness at 11-14 weeks of gestation has also emerged over the last few years as a novel and important marker for major cardiac abnormalities. This has further increased the interest in imaging the fetal heart early in the pregnancy.

Clinical impact of first and early second trimester fetal echocardiography on high risk pregnancies

OBJECTIVE

To evaluate the clinical impact of fetal echocardiography before 16 weeks' gestation on the management of pregnancies with fetuses at risk of congenital heart disease.

DESIGN AND SETTING

Observational study in a fetal medicine unit.

PARTICIPANTS AND METHODS

222 consecutive women with high risk pregnancies (230 fetuses) underwent transabdominal fetal echocardiography at a median gestation of 14(+1) weeks. For 10%, transvaginal scans were also performed. Criteria for normal scans were normal sequential segmental analysis, symmetrical four chamber view, normal semilunar valves, arterial outflow tracts, and ductal and aortic arches. Early scans were compared with mid-second trimester fetal echocardiography. Postmortem and postnatal data were added. Adverse pregnancy outcomes were diagnosis of a major cardiac or extracardiac abnormality, chromosomal defects, intrauterine death, or termination of pregnancy.

RESULTS

There were 21 abnormal cardiac scans (9%): 14 major structural defects (eight isolated, six with chromosomal or extracardiac abnormalities) in pregnancies resulting in three live births, one intrauterine death, and 10 terminated pregnancies. Seven scans showed asymmetry between right and left sided structures (two isolated, five with chromosomal or extracardiac abnormalities); six of the seven pregnancies were terminated. The scans were normal in 199 cases (87%). Cardiac follow up of 184 of 199 babies (93%) confirmed situs and connections. One case each of pulmonary stenosis and ventricular septal defect requiring postnatal intervention were diagnosed at later scans. In 28 of 199 (14%) babies there was a non-cardiac adverse outcome. First examination was not diagnostic for 10 (4%).

CONCLUSION

Early fetal echocardiography in high risk pregnancies was diagnostic in 96%. Abnormal cardiac scans (isolated in 48%, major structural defects in 67%) led to termination of pregnancy in 76%. Most cardiac scans were normal, allowing family reassurance. The high number of adverse outcomes with normal cardiac anatomy stresses the need for a multidisciplinary approach to early fetal echocardiography.

Improving the effectiveness of routine prenatal screening for major congenital heart defects

OBJECTIVE

To evaluate the effectiveness of adding outlet views to the four chamber view in routine prenatal ultrasound screening for major congenital heart defects (CHD) as performed by trained sonographers, and to compare the procedure with current practice.

DESIGN AND SETTING

Prospective observational study at a London teaching hospital.

PARTICIPANTS AND METHODS

9277 women booked at a single institution (80% had first trimester nuchal translucency measurement) due to have routine fetal cardiac screening using the four chamber and outflow tract views at > 18 weeks of gestation.

MAIN OUTCOME MEASURE

Identification of major CHD in chromosomally normal and abnormal pregnancies antenatally or postnatally.

RESULTS

There were 40 abnormalities (4.3/1000), of which 30 were chromosomally normal (3.3/1000). The overall antenatal detection rate was 75% (95% confidence interval (CI) 59% to 87%) and 70% (95% CI 51% to 85%) for euploid pregnancies. Abnormal cardiac views accounted for 70% of all prenatal diagnoses, 30% of which were made at < or = 18 weeks. The sensitivity of cardiac views during the first scan at > 18 weeks was 52%. Of all patients undergoing nuchal translucency screening, 34 had major CHD, nine with increased nuchal translucency (26.5%). Factors influencing the results of this screening programme were training and audit of operators, adequate equipment for antenatal examination, ease of access, and low threshold for referral to specialised fetal echocardiography.

CONCLUSION

Adding ventricular outlet views to the four chamber assessment of the heart at routine fetal anomaly scans at > 18 weeks is the most effective technique to detect CHD prenatally. The success of such a programme depends on an infrastructure committed to continuous in house training of obstetric ultrasonographers coupled with feedback from specialised fetal cardiologists, as well as adequate resource allocation to obstetric hospitals involved with antenatal screening.

The human ductus venosus between 13 and 17 weeks of gestation: histological and morphometric studies

BACKGROUND

Doppler studies of the ductus venosus are increasingly being integrated in the assessment of fetal well-being. Establishing the precise morphology and structure of the ductus venosus would provide a better understanding of Doppler findings during fetal adaptation. There is conflicting evidence from previous studies about the structure of the ductus venosus, especially with regard to the presence of a sphincter at the ductus venosus inlet. The aim of this study was to examine the morphology and histological structure of the ductus venosus wall and surrounding tissues at 13-17 weeks' gestation.

DESIGN

This was a prospective study on 28 fetuses obtained from medical termination of pregnancies between 13 and 17 weeks' gestation. Scanning electron microscopy and histological and immunohistochemical studies were carried out on ductus venosus sections obtained from different spatial planes.

RESULTS

The inlet of the ductus venosus contained a shelf which was rich in elastin, but devoid of any evidence of a smooth muscle sphincter. The isthmus of the ductus venosus above the inlet was narrowed, giving the lumen of the vessel an hourglass appearance. The endothelial surface of the ductus venosus, above the level of the inlet, showed longitudinal corrugations along its entire length. Longitudinally arranged elastin fibers were also seen along the length of the ductus venosus. A single layer of longitudinally arranged smooth muscle cells was present along the entire length of the ductus venosus, with occasional individual nerve cells visible in this layer.

CONCLUSIONS

The presence of an elastin-rich shelf and a narrow ductus venosus inlet orifice may act to accelerate flow from the portal sinus into a high-velocity system in the ductus venosus. The abundant elastin fibers in the adventitia of the ductus venosus may help antegrade wave propagation by elastic recoil. This study clearly demonstrates the lack of an anatomical smooth muscle sphincter at the ductus venosus inlet. However, the combination of endothelial corrugations and innervated smooth muscle support the hypothesis that the ductus venosus is an actively regulated vessel with the capacity to rapidly change diameter along its entire length in response to certain stimuli.

The anatomy of the umbilical, portal and hepatic venous systems in the human fetus at 14-19 weeks of gestation

BACKGROUND

Ultrasound imaging of the fetal ductus venosus is becoming increasingly commonplace in clinical practice. The true anatomical relationships of the fetal umbilical and portal venous systems have not been clearly defined due to paucity of published data on the relevant anatomy. This has led to confusing terminology when describing the fetal umbilical, portal and hepatic circulations. The aim of the present study was to examine and document the anatomy of the umbilical, portal and hepatic venous systems and to propose a standardized nomenclature.

METHODS

This was a prospective study on 11 fetuses obtained from medical termination of pregnancies between 14 and 19 weeks of gestation. The liver was microdissected to expose the branching pattern and anatomical relations of the umbilical, portal and hepatic venous systems.

RESULTS

A wide L-shaped venous confluence at the terminal end of the umbilical vein, termed the portal sinus, was identified. The portal sinus was connected to the right and left hepatic lobes, by the right and left intrahepatic portal veins, respectively. The extrahepatic portal vein drained into the portal sinus just before the origin of the right intrahepatic portal vein. The ductus venosus, a branchless straight vessel, originated from the portal sinus and ascended steeply in the direction of the diaphragm. Numerous small vessels draining the liver converged into three main hepatic veins, which open into the subdiaphragmatic vestibulum.

CONCLUSION

Based on detailed sequential anatomical dissection and clear illustrations, the present study documents the anatomy of the umbilical, portal and hepatic venous systems. Taking into account the embryological origin of the vessels, a new anatomically appropriate and simplified nomenclature of these venous systems is proposed. In clinical practice, the consistent use of the suggested terminology would allow collection of comparable data between units and enable operators to be confident of which vessels they are sampling by Doppler ultrasound.

Right and left ventricular long-axis function in the fetus using angular M-mode

OBJECTIVE

Long-axis function is determined by the longitudinally oriented myocardial fibers. Postnatally, conventional M-mode is used to assess tricuspid and mitral valve ring movements in relation to the cardiac apex. During fetal life, this is precluded by variable fetal position. We assessed the feasibility of determining right and left ventricular long-axis function in the fetus.

METHODS

A prospective, pilot study. The four-chamber view obtained during routine fetal echocardiography was recorded in a cineloop to which B-mode guided M-mode echocardiography was applied using angular M-mode. This allowed retrospective and correct placement of the cursor line from cardiac apex to tricuspid or mitral valve rings. M-mode tracings of the valve ring movements in relation to the apex were derived from the originally stored loop. Data from 18 fetuses (17-29 weeks of gestation) were available for analysis. Total excursion of the valve rings was measured offline. A second cursor line was simultaneously placed in the left ventricular outflow tract during color flow mapping for timing purposes (n = 6).

RESULTS

Right and left ventricular long-axis recordings were obtained in 18 and 14 cases, respectively. Total right ventricular excursion was 5.2 mm (SD, 0.9 mm) (range, 3.9-7.2 mm). Total left ventricular free wall excursion was 4.5 mm (SD, 1.1 mm) (range, 3.0-6.8 mm). For paired data, the mean of differences (right ventricle-left ventricle) was 0.8 mm (95% confidence interval 0.5-1.2). The valve rings moved towards the apex during systole (shortening) and away from it during diastole (lengthening). Peak downward movement coincided with cessation of aortic flow and diastolic lengthening with flow through the atrioventricular valves.

CONCLUSION

Long-axis function in the fetus is feasible if M-mode angle correction is used. There was no clinically significant difference between tricuspid and mitral valve excursions. The pattern of atrioventricular valve movement is coordinate and similar to that of adults. Long-axis function offers a new avenue to study systolic and diastolic function in the fetus.

Isolated echogenic foci in the fetal heart: do they increase the risk of trisomy 21 in a population previously screened by nuchal translucency?

OBJECTIVES

To confirm the hypothesis that isolated cardiac echogenic foci at the second-trimester anomaly scan do not influence our current calculation of risk of trisomy 21 in individual pregnancies, which is based on maternal age and nuchal translucency thickness at 11-14 weeks.

DESIGN

Observational study in a fetal medicine unit.

METHODS

In a general pregnant population undergoing first-trimester nuchal translucency screening, data from 239 singleton pregnancies with isolated cardiac echogenic foci at the second-trimester anomaly scan were compared with those of a control group of 7449 pregnancies with normal anomaly scans. Prevalence of trisomy 21 was determined in both groups. Following the anomaly scan, the individual risks of trisomy 21 were calculated by adjusting the previous risk based on maternal age and first-trimester nuchal translucency. We assumed that echogenic foci did not alter each individual risk calculation. The expected number of cases of Down syndrome in both groups was then calculated from the sum of probabilities of each individual affected fetus. The observed number of cases was compared with the expected number in both study and control populations.

RESULTS

There was no statistically significant difference between the prevalence of trisomy 21 in the study group (no cases) and in the control population (three cases). From individual risk calculations, observing no cases of trisomy 21 in the study group was the most likely event if echogenic foci did not increase the risk of this chromosomal abnormality (P = 0.62).

CONCLUSION

The finding of isolated echogenic foci at the time of the 20 week-scan does not significantly change the risks of trisomy 21 if background risk and previous nuchal translucency measurements are taken into account in the individual risk calculation. We suggest that no further adjustments to risk should be used.