Ultrasonography and Doppler studies in twin-to-twin transfusion syndrome

Fetal Heart Size: A Comparison Between the Point-to-Point Trace and Automated Ellipse Methods Between 20 and 40 Weeks' Gestation

OBJECTIVES

To evaluate whether the global area and circumference of the heart varies between two measurement techniques: the point-to-point trace and the electronic ellipse methods.

METHODS

The epicardial border of the 4-chamber view was measured in 200 fetuses between 20 and 40 weeks' gestation, from which the area and circumference using the point-to-point trace and electronic ellipse were measured. Analysis of variance, correlation, and regression analysis using fractional polynomials and 7 independent variables (head circumference, biparietal diameter, abdominal circumference, femur length, estimated fetal weight, mean ultrasound gestational age, and last menstrual period gestational age) were performed.

RESULTS

The correlation between the mean ultrasound gestational age and last menstrual period gestational age was 0.9880 (5% confidence limit, 0.9716; 95% confidence limit, 0.9880), with an R² of 0.9762. The R² value for the 7 independent variables regressed against the area and circumference using the point-to-point trace and electronic ellipse methods ranged between 0.885 and 0.965. Comparison of Z scores between this study and previous publications demonstrated that there were differences and similarities, depending on whether the area or circumference was measured.

CONCLUSIONS

This study shows high R² values when comparing measurements of the area and circumference against 7 independent variables, irrespective of whether the point-to-point trace or the electronic ellipse method was used to obtain the measurements. A calculator to evaluate the area and circumference is provided, using 7 independent variables from which Z scores and percentiles for individual measurements can be computed.

Twin-to-Twin Transfusion Syndrome: Definition, Staging, and Ultrasound Assessment

Objective: The purpose of this article is to review the definition of twin-to-twin transfusion syndrome (TTTS) and the sonographic diagnostic assessment of these cases prior to therapy.

Materials and Methods: The article addresses the terminology used to refer to the condition and describes the systematic ultrasound assessment of the condition, including the ultrasound diagnosis, the staging of the disease, cervical assessment and pre-operative mapping.

Results: From an etymologic and medical point of view, the term ‘fetofetal transfusion’ is more appropriate than ‘TTTS’. However, as the latter, and its attendant acronym TTTS, have been widely adopted in the English language, it is impractical to change at this point. TTTS is defined sonographically in the combined presence of a maximum vertical pocket (MVP) of 8 cm or greater in one sac and 2 cm or less in the other sac, regardless of the gestational age at diagnosis. Staging of the condition using the Quintero staging system is practical, reproducible, and accepted. Transvaginal cervical length assessment should be an integral part of the ultrasound evaluation. Pre-operative mapping to anticipate the location of the placental vascular anastomoses and avoid injuring the dividing membrane is also discussed.

Conclusions: The term ‘TTTS’ can continue to be used in the English medical literature. The condition can be diagnosed and assessed following a systematic ultrasound methodology. The use of such ultrasound methodology breaks the examination into a distinct set of components, assuring a comprehensive examination and proper communication among caregivers.

Twin-twin transfusion syndrome

The understanding and management of twin-twin transfusion syndrome has evolved significantly over the past few years. Improved and standardized sonographic diagnostic criteria, understanding of the heterogeneic nature of the syndrome, development of an anatomical and reproducible surgical technique for the identification of vascular anastomoses, and technological advances and developments now allow clinicians to view the disease as a more readily understandable and treatable condition. Many tasks remain, including education of peers, better screening and diagnosis, and further development of surgical instruments. Generalization of treatment outcomes should no longer apply given the varied results with disease stage. Confirmation of our tailored approach to management of the disease according to stage should soon be corroborated with an appropriate clinical trial.

Doppler ultrasound in multiple pregnancies

This chapter aims to provide a current review of the use of Doppler ultrasound in the management of multiple pregnancies. OVID and Medline searches were undertaken. Randomized controlled trials, where available, were assessed by the Cochrane Review Manager (RevMan-version 3.0). The specific multiple pregnancy problems of fetal growth restriction (FGR), twin reversed arterial perfusion sequence and twin-twin transfusion syndrome (TTTS) were also reviewed. Historically, controlled and randomized controlled trials show a promising reduction in perinatal mortality in twin pregnancies where Doppler ultrasound is used. However, the numbers are small and further trials are recommended. In those twin pregnancies in which there is FGR as a result of placental dysfunction, Doppler ultrasonography will show intertwin discordancy. In those twin pairs where development is complicated by TTTS, there is often discordant fetal size, with concordant fetal Doppler results. Thus Doppler ultrasound appears to be useful in the management of twin pregnancies and in delineating those complicated by FGR and TTTS.

Clinical and echographic features of in utero cardiac dysfunction in the recipient twin in twin-twin transfusion syndrome

OBJECTIVE

Fetal twin-twin transfusion syndrome (TTTS) presenting in the second trimester has been associated with almost no perinatal survival until recently, when serial drainage of amniotic fluid has improved the prognosis to 70%-80%. Most recipient twins now survive but develop cardiac dysfunction. The study was undertaken to evaluate the abnormal echocardiographic features and clinical complications of cardiac disease in the recipient twin of TTTS.

DESIGN

Antenatal and postnatal echocardiographic and clinical observational study.

SETTING

Antenatal studies in a tertiary referral centre. Postnatal management and follow up were performed by the same paediatric cardiologist, either at the obstetric hospital or at the regional referral centre.

PATIENTS

Twin pregnancies complicated by TTTS with severe polyhydramnios diagnosed earlier than 25 weeks that proceeded until viability (n = 5).

INTERVENTION

Serial fetal echocardiography with colour Doppler. Postnatal echocardiography in the first week and between two and seven months. Serial amnioreduction was performed in all pregnancies. Digoxin treatment, pericardiocentesis, paracentesis, or laser ablation of placental anastomoses was undertaken when there was hydrops.

RESULTS

Increased cardiothoracic ratio and tricuspid regurgitation were seen in all recipient twins. High pulmonary artery velocities developed in three. One recipient twin died a week after delivery of endocardial fibroelastosis and infundibular pulmonary stenosis. Two other had balloon dilatation for pulmonary stenosis, one shortly after birth and one at four months. A further twin has apical thickening of the right ventricle at six months. The remaining recipient twin had normal echocardiographic findings at follow up.

CONCLUSION

This report characterises for the first time a cardiac disease acquired in utero in the recipient twin in pregnancies complicated by TTTS. Clinical manifestations in utero range from mild to critical pulmonary stenosis or lethal cardiomyopathy. Although perinatal prognosis seems to be related to the severity of dysfunction when first diagnosed in utero, follow up in infancy is recommended in view of the possibility of progressive pulmonary stenosis.