Echocardiographic diagnosis of fetal heart defects in mid trimester

Comparative analysis of pattern, management and outcome of pre- versus postnatally diagnosed major congenital heart disease: a population-based study

OBJECTIVES

Most pregnant women in New South Wales undergo obstetric ultrasound examination, including some assessment of fetal cardiac anatomy. We aimed to review the spectrum of cardiac defects, management and outcome data of all fetuses with diagnosis of major congenital heart disease between 1994 and 1996 and compare them to major congenital heart disease in infants born during the same 3-year study period.

METHODS

Descriptive comprehensive study of the New South Wales population. Study centers included the single fetal echocardiographic referral service and the two pediatric cardiac centers of New South Wales.

RESULTS

Ninety-seven fetuses and 562 infants with major congenital heart disease were identified (240,000 livebirths), resulting in a prenatal detection rate of 15%. Anomalies detectable by cardiac four-chamber views were diagnosed at an average rate of 30% (68/229) in utero. By contrast, lesions associated with abnormal ventricular outflow and great artery views were detected in only 6.7% (29/430; P < 0.0001) of cases prior to birth. Of the 97 fetuses, 29 were aborted, 16 died in utero, and 9 died early postnatally without treatment. Within 2 weeks of age, 23% with fetal and 40% (P < 0.05) with infant major congenital heart disease diagnosis required an intervention, mainly for patent ductus arteriosus dependent lesions. Postnatal survival was similar for the fetal and infant series up to 2 years of age: 77% (95% confidence interval 64-90%) vs. 85% (95% confidence interval 82-88%).

CONCLUSIONS

Prenatal diagnosis has important implications for pregnancy outcome, in particular for univentricular lesions. However, the present mode of obstetric routine ultrasound scanning fails to identify most ductus arteriosus dependent cardiac lesions with a predictable need for early postnatal intervention.

Left atrial isomerism detected in fetal life

Left and right atrial isomerism, comprising congenital heart defects with disturbances in normal left-right asymmetry, are phenotypically distinct after birth, although animal models suggest a common embryologic origin. We postulated that the prenatal phenotype may indeed be similar in both syndromes but that differential fetal loss is responsible for the distinct postnatal phenotypes. Distinctive fetal echocardiographic features of these syndromes have not been described in detail. We therefore sought markers of left atrial isomerism that could be recognized prenatally by echocardiography and compared our results with postnatal data to identify unique intrauterine features. We reviewed 10 cases at our center and 28 published cases of cardiac malformations with atrial isomerism detected by fetal echocardiography. Postnatal imaging and autopsies provided definitive diagnoses. Ninety-five percent of cases exhibited left atrial isomerism and formed the primary study population. Echocardiographic markers included a large azygos continuation of an interrupted inferior vena cava, atrioventricular block with structural heart disease, and viscerocardiac heterotaxy. At least 1 of these markers was seen in all of our center's cases. The incidences of most cardiac lesions detected prenatally were similar to those detected postnatally. However, although the incidences of atrioventricular septal defect and pulmonary outflow obstruction in live births were 50% and 45%, respectively, they were found much more frequently among stillbirths (80% each). In summary, we identified key fetal echocardiographic features highly sensitive for left atrial isomerism. Fetal loss selects against certain lesions such as atrioventricular septal defect. The spectrum of cardiac disease suggests a greater primitivity of the fetal heart than previously shown; the typical cardiac phenotypes are closer to right atrial isomerism than are their extrauterine presentations.

Outcome of prenatally detected cardiac malformations

Reliable, prenatal detection of congenital heart disease has become possible over the past decade with the evolution of fetal echocardiography. We have documented the outcome of 170 cardiac defects diagnosed prenatally since 1984. Of 170 cases, 55 (32%) had major extracardiac malformations and 45 (28%) chromosomal abnormalities (16 had both). Elective termination was chosen in 77 (45%) pregnancies. Of 93 continuing pregnancies 15 were stillborn and 43 died postnatally (48% of these fetuses and infants had extracardiac or chromosomal anomalies, or both). Thirty-five patients survive at 1 to 80 months (mean 36). Aneuploidy or extracardiac defects are present in 20% of survivors. Nonimmune hydrops secondary to cardiac failure was present in 7 continuing pregnancies and none of these patients survived. The prognosis of prenatally diagnosed cardiac lesions is negatively influenced by the presence of cardiac failure, aneuploidy or extracardiac malformations, or a combination of these. Optimal counseling and management requires the identification of these conditions when present.

Fetal echocardiography: accuracy and limitations in a population at high and low risk for heart defects

OBJECTIVE

Our objective was to assess the accuracy of prenatal echocardiography in detecting congenital heart defects in patients at high and low risk for structural cardiac anomalies.

STUDY DESIGN

Sixty-nine consecutive fetuses with congenital heart defects who had had prenatal ultrasonography at greater than or equal to 18 weeks' gestation were evaluated to determine the accuracy of prenatal ultrasonography in identifying structural cardiac defects. Thirty-nine patients were at high risk and 30 patients were at low risk for cardiac anomalies. All fetuses were scanned with standard four-chamber and outflow tract views. Data concerning extracardiac anomalies and karyotypic abnormalities were tabulated. The accuracy of the four-chamber view alone in identifying congenital heart defects was evaluated.

RESULTS

Fifty-seven of 69 fetuses (83%) were prenatally identified ultrasonographically as having a heart defect. There was no difference in the sensitivity of detecting cardiac anomalies between high-risk and low-risk groups. When the four-chamber view was used, only 63% of fetuses were recognized as having an abnormal heart. Extracardiac anomalies were noted in 36% and karyotypic abnormalities in 17% of patients.

CONCLUSION

The four-chamber and outflow tract views done routinely in an ultrasonography laboratory seeing a mixed population of patients was successful in detecting 83% of fetuses with structural cardiac malformations. Because 43% of the fetuses with heart defects were referred for low-risk indications, systematic ultrasonographic examination of the fetal heart should not be reserved only for those at high risk.