Screening for fetal cardiac malformations

The impact of prenatal diagnosis of congenital heart disease on pediatric cardiology and cardiac surgery

Since the early 1980s prenatal diagnosis of congenital heart disease (CHD) has progressively impacted on the practice of pediatric cardiology and cardiac surgery. Fetal cardiology today raises special needs in screening programs, training of the involved staff, and allocations of services. Due to the increased detection rate and to the substantial number of terminations, the reduced incidence of CHD at birth can affect the workload of centers of pediatric cardiology and surgery. In utero transportation and competition among centers may change the area of referral in favor of the best centers. Echocardiography is a powerful means to diagnose and to guide lifesaving medical treatment of sustained tachyarrhythmias in the fetus. Prenatal diagnosis not only improves the preoperative conditions in most cases but also postoperative morbidity and mortality in selected types of CHD. Intrauterine transcatheter valvuloplasty in severe outflow obstructive lesions has been disappointing so far and this technique remains investigational, until its benefits are determined by controlled trials. Prenatal diagnosis allows counselling of families which are better prepared for the foreseeable management and outcome of the fetus. These benefits can reduce the risks of litigation for missed ultrasound diagnosis. As increased costs can be expected in institutions dealing with a large number of fetal CHD, the administrators of these institutions should receive protected funds, proportional to their needs.

Three-vessel view of the fetal heart: In utero development of the great vessels

OBJECTIVES

The purpose of our study is to provide reference values for the great vessels obtained from images of the three-vessel view of the fetal heart, with an emphasis on the size discrepancy of the great vessels.

METHODS

From February 2003 to May 2003, the main pulmonary artery (MPA), ascending aorta (AA), and SVC were measured in well-dated, nonanomalous fetuses scanned at 14-38 weeks of gestation.

RESULTS

The size of each great vessel had a significant positive relationship with advance in gestation (P < 0.001); MPA (mm) = -2.76 + 0.34 x GA, ascending aorta (AA) (mm) = -1.73 + 0.26 x GA - 1.18E - 05 x GA(3), and SVC (mm) = 0.33 + 0.01 x GA(2) - 4.12E - 05 x GA(3). The AA/MPA ratio was significantly decreased with advance in gestation, while the SVC/AA ratio was significantly increased; AA/MPA ratio = -1.24 - 0.03 x GA + 3.88E - 04 x GA(2); P < 0.001, SVC/AA ratio = 0.63 - 5.43E - 03 x GA + 1.96E - 04 x GA(2); P < 0.001.

CONCLUSION

On the three-vessel view of the fetal heart, the interpretation of the size discrepancy of the great vessels needs to be adjusted according to fetal growth.

Indications for fetal echocardiography

Congenital heart disease is one of the most common congenital malformations diagnosed in liveborns. As more women undergo prenatal diagnosis, the need for screening fetal echocadiography increases. The fetal, maternal, and familial indications for fetal echocadiography are outlined in order to improve the identification of women in greatest need for this screening modality.

The three vessels and trachea view (3VT) in fetal cardiac scanning

OBJECTIVE

Comprehensive evaluation of the fetal heart has become a major part of targeted organ scanning to rule out fetal malformations. Evaluation of the mediastinal major vessels seems to be the most difficult and time-consuming part of fetal heart examination. Our aim was to define and evaluate the three vessels and trachea (3VT) view, a novel and simple method to examine the great vessels in the mediastinum, and its applicability in the clinical practice of fetal echocardiography, while establishing nomograms for cardiac vessel measurements obtained in this view.

METHODS

The three vessels and trachea view was examined in 379 low-risk gravidae between 14+0 and 23+6 weeks' gestation. Six parameters in this plane were measured to establish nomograms. In another group of 984 mixed high- and low-risk patients we compared the time required to identify the aortic arch using the 3VT view as compared to the long-axis view.

RESULTS

The 3VT view was readily and satisfactorily demonstrated in all but two of the 1363 cases examined. In 17 cases (out of a total of 982) more than 10 min were required to identify the aortic arch using the 3VT view and in 71 patients when employing the long-axis view (P < 0.001).

CONCLUSION

The clinical applicability of the 3VT view to evaluate the anatomy of the major vessels in the mediastinum is demonstrated. Although a wide variation in the six parameters of the 3VT view used here precludes their use in diagnosing great vessel anomalies, some of the ratios between them have promising potential in the evaluation of great vessel malformations. Further, the 3VT view seems to be more efficient in identifying the aortic arch than does the long-axis view.

Prenatal diagnosis of congenital heart disease in the northern region of England: benefits of a training programme for obstetric ultrasonographers

OBJECTIVE

To examine the results of fetal cardiac scanning and audit the changes in performance resulting from the introduction of a training programme for obstetric ultrasonographers.

METHODS

Using the database of the Northern Regional Congenital Abnormality Survey (NORCAS), fetuses with complex or significant congenital heart disease (CCHD) diagnosed prenatally in 1994 were identified. A simple programme of centralised and local training was instituted in 1995 by the department of paediatric cardiology to teach obstetric ultrasonographers in district general hospital maternity departments to identify congenital heart malformations. The results of the training programme were assessed by comparing the 1994 identification rate of CCHD with the rates for 1996 and 1997.

RESULTS

Birth rate fell during the study from 35,026 in 1994 to 32,874 in 1997. Registration of CCHD also fell, from 115 in 1994 to 87 in 1997. Prenatal recognition of CCHD rose from 17% in 1994 to 30% in 1995 and 36% in 1996. In 1997 it fell slightly to 26.9%. The total number of scans did not change much year on year, but the number of parents choosing termination increased significantly (from 22.7% to 57%).

CONCLUSIONS

A simple training programme for obstetric ultrasonographers increased their ability to detect serious congenital heart disease at a routine 18-20 week anomaly scan. With a termination rate of more than 50%, the incidence of CCHD in the population fell from 3.3/1000 to 2.6/1000 live births. This audit, conducted within a stable population using ascertainment by a well established fetal malformation registry, suggests that prenatal diagnosis may have a significant effect on the incidence of complex or serious congenital cardiac malformations.

Temporal variability in birth prevalence of cardiovascular malformations

OBJECTIVE

To investigate changes over time in the prevalence at live birth of cardiovascular malformations and to compare "anatomical" and "physiological" diagnostic hierarchies within a population.

DESIGN

Retrospective and prospective ascertainment of all congenital cardiovascular malformations diagnosed in infancy.

SETTING

The resident population of one health region.

PATIENTS

All infants live born from 1985 to 1997 with cardiovascular malformations confirmed by echocardiography, cardiac catheterisation, surgery or autopsy.

MAIN OUTCOME MEASURES

Year to year variation in prevalence of individual malformations and of "complex", "significant", and "minor" groups.

RESULTS

2671 babies with cardiovascular malformations were confirmed in a denominator population of 477 960 live births (5.6 per 1000). There was no change over 13 years in the birth prevalence of "complex" or "significant" defects, but a highly significant increase in "minor" defects (p < 0.0001), mainly small ventricular septal defects. Termination of pregnancy increased from no cases in 1985 to 16 in 1997 with no demonstrable effect on live born babies with heart defects. A one dimensional "anatomical" diagnostic hierarchy led to under ascertainment of pulmonary atresia by 27%, coarctation of the aorta by 39%, and interruption of the aorta by 100%.

CONCLUSIONS

The apparent increase in live born cardiovascular malformations results mainly from improved diagnosis of minor defects. There has been no change over time in birth prevalence of more serious defects. Spontaneous year to year variation in numbers will make it difficult to ascribe any short term changes to any particular intervention. A two dimensional diagnostic hierarchy is offered as a standard.

Evolution and long term outcome in cases with fetal diagnosis of congenital heart disease: Italian multicentre study. Fetal Cardiology Study Group of the Italian Society of Pediatric Cardiology

OBJECTIVES

To analyse the evolution and outcome in utero and after birth of infants with a fetal diagnosis of congenital heart disease.

DESIGN

Inclusion criteria were the fetal diagnosis of congenital heart disease, confirmed postnatally or postmortem, and a complete follow up in utero and after birth.

SETTING

20 centres operating prenatal echocardiographic screening.

PATIENTS

847 cases were included in the study. Gestational age at diagnosis ranged from 15-39 weeks; in 370 cases (43.7%) the diagnosis was made before 24 weeks' gestation.

RESULTS

245/847 cases (28.9%) were terminated during pregnancy, 227 following early diagnosis; 128/245 cases (52. 2%) had associated anomalies and 117/245 (47.8%) had serious congenital heart disease. Of the remaining 602 cases that continued the pregnancy, 72 (11.9%) died in utero, 259 (43%) died postnatally (83 after surgery or invasive procedures), and 271 infants (45%) survived and presently range in age from 18 months to 13 years old. The mortality rate was higher in cases with associated extracardiac or chromosomal anomalies (68% and 74% of cases continuing pregnancy, respectively), and in cases with heart failure and complex cardiac defects.

CONCLUSIONS

The data confirm a relevant fetal and postnatal loss in cases with complex congenital heart disease, and major clinical use of prenatal diagnosis in the management of ductus dependent anomalies. Negative prognostic factors for the outcome were associated anomalies and heart failure.

Current and potential impact of fetal diagnosis on prevalence and spectrum of serious congenital heart disease at term in the UK. British Paediatric Cardiac Association

BACKGROUND

Assessment of the effect of fetal diagnosis on the prevalence of congenital heart disease at term requires national ascertainment because referral patterns are not rigorously structured.

METHODS

Between 1993 and 1995, all 17 paediatric cardiac centres in the UK submitted to a database lists of all fetuses diagnosed, and all infants needing surgery or interventional catheterisation or dying in the first year of life because of structural heart disease; details included the postal area of residence.

FINDINGS

There were 4799 affected pregnancies, 4165 babies born alive, 1124 fetal diagnoses, and 567 terminations of pregnancy because the fetus had structural heart disease. Thus, a fetal diagnosis was made in 23.4% of affected pregnancies (11.7% of all affected livebirths) with geographical variability in diagnostic rates.

INTERPRETATION

Fetal cardiac screening has an effect on the prevalence and types of congenital heart disease seen at term because many affected pregnancies are terminated. If detection rates of affected fetuses rose nationally to those seen in the 15 postal areas where detection rates were significantly higher than the national average in 1993-95, we would expect about 218 fewer affected individuals to be born annually.

[Fetal echocardiography]

Cardiac malformations are the most frequent and serious fetal malformations. However their prenatal diagnosis is the less easy. Fetal echocardiography is the main diagnostic tool; in addition it is helpful for the therapeutic orientation. Only 30% of fetal heart diseases are detected on account of maternal or fetal indications, most of them being discovered without any known risk factor. In order to improve its diagnostic sensitivity, fetal echocardiography must include a four chambers view and a study of ventricular and arterial connection. Nevertheless, many heart diseases remain undetected, most of them being minor with favorable prognosis. Search of an extracardiac abnormality and karyotype analysis must be performed in order to explicit the prognosis. Fetal arrhythmias can be analyzed by study of the atrial and ventricular contraction using M-mode echocardiogram or Doppler mode; most of them are supraventricular and accessible to maternal therapy. The sustained fetal bradycardia is frequently a complete heart block whose prognosis depends upon its association with a heart defect and/or a ventricular escape. Antibodies SS-A and SS-B are frequently associated with complete heart block without structural heart defects. Hypertrophic cardiomyopathy may be observed in fetus of diabetic mothers needing an accurate evaluation of the thickness of the interventricular septum. Echocardiography is a part of fetal medicine, which includes the different specialties devoted to the fetus.

Pulmonary atresia with intact ventricular septum: impact of fetal echocardiography on incidence at birth and postnatal outcome. UK and Eire Collaborative Study of Pulmonary Atresia with Intact Ventricular Septum

BACKGROUND

Fetal echocardiography is widely established in the United Kingdom for prenatal diagnosis of congenital heart disease. This may result in a substantial reduction in incidence at birth because of selected termination of pregnancy. The objective of this population-based study was to determine the incidence of pulmonary atresia with intact ventricular septum (PAIVS) at birth, the impact of fetal echocardiography on this incidence, and to compare the outcome of cases with and those without prenatal diagnosis.

METHODS AND RESULTS

From 1991 to 1995, all infants born with PAIVS and all fetal diagnoses in the United Kingdom and Eire were studied. There were 183 live births (incidence 4.5/100,000 live births). The incidence was 4.1 cases per 100,000 live births in England and Wales, 4.7 in Scotland, 6.8 in Eire, and 9.6 in Northern Ireland (P=0.01). There were 86 fetal diagnoses made at a mean of 22.0 weeks of gestation leading to 53 terminations of pregnancy (61%), 4 intrauterine deaths (5%), and 29 live births (34%). The incidence at birth would be 5.6 per 100,000 births in England and Wales, 5.3 in Scotland, and unchanged in Eire and Northern Ireland, if there were no terminations of pregnancy and assuming no further spontaneous fetal deaths (P=0.28). An initial diagnosis of critical pulmonary stenosis was made in 6 cases, at a mean of 22.3 weeks of gestation with progression to PAIVS by 31.4 weeks. Probability of survival at 1 year was 65% and was the same for live-born infants whether or not a fetal diagnosis had been made.

CONCLUSIONS

PAIVS is rare, occurring in 1 in 22,000 live births in the United Kingdom and Eire. Termination of pregnancy has resulted in an important reduction in the live-born incidence in mainland Britain.

Normal fetal cardiac dimensions obtained by perpendicular imaging

This study provides normal fetal cardiac dimensional data in a large patient group over a wide range of gestational ages. Perpendicular imaging decreased lateral resolution error, resulting in normal values with narrower confidence limits than in prior studies.

Outcome of fetuses with heart disease diagnosed in utero

OBJECTIVE

To review the outcomes of 193 fetuses with cardiac abnormalities detected by echocardiography.

METHODS

A total of 422 fetuses between 16 and 41 gestational weeks, referred to paediatric cardiologists for detailed echocardiography, were included in this study.

RESULTS

Structural heart defects were found in 55 (28%), isolated arrhythmia in 105 (54%), and other non-structural abnormalities (dilated cardiomyopathy, hypertrophic cardiomyopathy, aneurysm of the foramen ovale, isolated pericardial effusion or echogenic foci) in 33 (17%) of 193 fetuses. Total mortality was 26%. The prognosis was poor in fetuses with structural heart defects; 37 of 55 cases (67%) died in utero or postnatally. Chromosomal abnormality was associated with structural heart defect in 38% of fetuses, of whom 38% died. Among fetuses with isolated arrhythmia survival was 95%. Poor outcome was associated with complete heart block (n = 14) in 2 (14%) fetuses with hydrops and heart rate of less than 55 per minute, and with supraventricular tachycardia (n = 21) in three (14%) neonates delivered prematurely at a mean gestational age of 33 weeks. Furthermore, nine of 12 fetuses (75%) with structural heart defects and arrhythmia died. Among fetuses with non-structural cardiac abnormalities, survival was 73%. Poor outcome was evident in fetuses with dilated cardiomyopathy in eight of 13 (62%) and with hypertrophic cardiomyopathy in one of eight (13%) of cases.

CONCLUSIONS

Factors associated with a poor prognosis were: structural heart defect associated with chromosomal abnormality or arrhythmia, congestive heart failure associated with supraventricular tachycardia or complete heart block, especially if delivery occurs preterm; and fetal hydrops with congestive heart failure and atrioventricular valve regurgitation.

Strategies for antenatal detection of Down's syndrome

AIM

To predict the effect of maternal serum screening and fetal echocardiography on the birth prevalence of Down's syndrome.

METHODS

The outcome of all Down's syndrome pregnancies in the Northern Health Region between 1985 and 1991 was retrospectively ascertained. The number and outcome of all Down's syndrome pregnancies were used to define a theoretical population which would exist in the absence of screening. Published reports were used to predict the effects of screening strategies.

RESULTS

Down's syndrome was identified in 412 pregnancies of which 315 (76%) resulted in live birth. A theoretical population with no antenatal screening would be expected to produce 31 stillbirths and 381 (92%) live births affected by Down's syndrome. In the same population a programme of maternal serum screening and fetal echocardiography would lead to 155 and 14 terminations, respectively, and when combined, would reduce affected live births to 229 (56%).

CONCLUSIONS

Even if maternal serum screening and fetal echocardiography achieve their predicted potential, around half of all pregnancies affected by Down's syndrome will result in live born babies.

Natural history of trisomy 18

It has been suggested that survival in babies with trisomy 18 may be better than previously recognised, and that cardiac surgery may be justified. A population based study spanning seven years in one English health region is presented. The fetal prevalence at 18 weeks was 1 in 4274 and birth prevalence 1 in 8333 live births. Trisomy 18 was detected antenatally in 43% of cases, but almost 90% of those born without a diagnosis were known to be growth retarded in utero. More than 50% of liveborn infants were delivered by caesarean section. The median survival of those born alive was 3 days with no babies living longer than one year. Cardiac malformations were not universal but were present in more than 87% of those for whom there were data. However, in only three cases were cardiac problems implicated in the death of the infants. Cardiac surgery is not likely to improve the survival of infants with trisomy 18 and at present cannot be justified. The most common mode of death was central apnoea.

Antenatal diagnosis of congenital heart disease and Down's syndrome: the potential effect on the practice of paediatric cardiology

OBJECTIVE

To predict the effect of antenatal ultrasound screening for congenital heart disease and maternal serum screening of Down's syndrome on the practice of paediatric cardiology and paediatric cardiac surgery.

DESIGN

A retrospective and prospective ascertainment of all congenital heart disease diagnosed in infancy in 1985-1991.

SETTING

One English health region.

PATIENTS

All congenital heart disease diagnosed in infancy by echocardiography, cardiac catheterisation, surgery, or necropsy was classified as "complex", "significant", or "minor" and as "detectable" or "not detectable" on a routine antenatal ultrasound scan.

RESULTS

1347 infants had congenital heart disease which was "complex" in 13%, "significant" in 55%, and "minor" in 32%. 15% of cases were "detectable" on routine antenatal ultrasound. Assuming 20% detection and termination of 67% of affected pregnancies, liveborn congenital heart disease would be reduced by 2%, infant mortality from congenital heart disease by 5%, and paediatric cardiac surgical activity by 3%. Maternal screening for Down's syndrome, assuming 75% uptake, 60% detection, and termination of all affected pregnancies, would reduce liveborn cases of Down's syndrome by 45%, liveborn cases of congenital heart disease by 3.5%, and cardiac surgery by 2.6%.

CONCLUSIONS

Screening for congenital heart disease using the four chamber view in routine obstetric examinations and maternal serum screening for Down's syndrome is likely to have only a small effect on the requirements for paediatric cardiology services and paediatric cardiac surgery.