Latest advances and topics in fetal echocardiography

Use of fetal echocardiography for characterization of fetal cardiac structure in women with normal pregnancies and gestational diabetes mellitus

OBJECTIVES

To assess fetal cardiac structure and function and to evaluate the efficacy of routine fetal echocardiography for detection of fetal cardiac abnormalities in women with normal pregnancies and those with gestational diabetes mellitus.

METHODS

In this prospective study, we studied fetal cardiac structure and function in 294 uncomplicated singleton pregnancies and 302 pregnancies complicated by gestational diabetes. Fetal echocardiography (2-dimensional sonography and pulsed wave Doppler imaging) was used to assess functional parameters and to detect any cardiac structural abnormality. Data from clinical and echocardiographic evaluations of neonates at birth and 3 months were obtained to confirm the antenatal findings.

RESULTS

The mean maternal age ± SD was 28.9 ± 5.0 years in the diabetes group and was comparable to that of women with normal pregnancies. The mean hemoglobin A1c value was 6.3%, and the mean body mass index was 28.0 kg/m(2). The systolic function as assessed by the ejection fraction increased significantly in the diabetes group compared to the normal pregnancy group independent of glycemic control (P < .001). The pulsed wave parameters (early diastolic peak flow velocity and early-to-late diastolic peak flow velocity ratio) were significantly different between the groups (P < .001). The interventricular septum and fetal ventricular wall thicknesses were significantly increased in the presence of gestational diabetes (P < .001). No major fetal cardiac structural anomaly was detected in either group. On follow-up after delivery, all neonates were assessed clinically and by transthoracic echocardiography to rule out congenital defects.

CONCLUSIONS

In our study, significant increases in the interventricular septum and ventricular wall thicknesses were detected in the presence of gestational diabetes mellitus. Interestingly, none of the neonates of pregnant women with gestational diabetes were found to have echocardiographic evidence of congenital heart disease.

The cardiac state diagram as a novel approach for the evaluation of pre- and post-ejection phases of the cardiac cycle in asphyxiated fetal lambs

The aim of this study was to investigate myocardial wall motion using echocardiography and color-coded tissue velocity imaging and to generate a cardiac state diagram for evaluation of the duration of the pre- and post-ejection phases in asphyxiated fetal lambs. Six near-term lambs were partly exteriorized and brought to cardiac arrest through asphyxia. Echocardiography measurements were recorded simultaneously with arterial blood sampling for lactate and blood gases. All fetal lambs exhibited prolongation of the pre- and post-ejection phases at the time when the most pronounced changes in lactate concentration and pH occurred. The mean change in duration of the pre- and post-ejection phases for all fetal lambs was 36 ± 7 ms (p < 0.002) and 77 ± 17 ms (p < 0.019), respectively, and the percentage change was 50% (p < 0.001) and 38% (p < 0.049), respectively. As asphyxia progressed in fetal lambs, the duration of the pre- and post-ejection phases increased. The cardiac state diagram has the potential to be a comprehensible tool for detecting fetal asphyxia.

Fetal tissue Doppler imaging in pregnancies complicated with preeclampsia with or without intrauterine growth restriction

OBJECTIVES

This study's aim was to evaluate the effect of preeclampsia and intrauterine growth restriction (IUGR) on fetal cardiac function, and the relationship of the latter with adverse pregnancy outcomes.

MATERIAL AND METHODS

We did a cross-sectional study of 132 women with uncomplicated singleton pregnancies, 34 with preeclampsia without IUGR, and 12 with preeclampsia and IUGR. Fetal cardiac structure and function were evaluated using fetal two-dimension ultrasound, pulsed wave Doppler and tissue Doppler imaging (TDI). Data were analyzed by t-tests, ANOVA, Chi-square tests, or Wilcoxon rank-sum test.

RESULTS

Compared with the normal pregnancy group, mitral/tricuspid early systolic peak velocity of annulus/late diastolic peak velocity of annulus (Sa) and left ventricular (LV)/right ventricular (RV) early diastolic peak velocity at the annulus (Ea) in TDI decreased in preeclampsia with or without IUGR (P < 0.05). LV/RV Ea underwent a gestational decrease in preeclampsia with or without IUGR (P < 0.05). The changes in mitral/tricuspid Sa and LV Sa associated with preeclampsia were even more pronounced with preterm delivery at less than 34 gestational weeks and stillbirth (P < 0.05).

CONCLUSIONS

Intrauterine growth restriction influences fetal cardiac function in the presence of preeclampsia, and TDI may be a sensitive and preferable method to detect such changes. Fetal LV/RV Ea is a potential marker for early fetal cardiac diastolic impairment, and mitral/tricuspid Sa and LV Sa may be predictors for adverse pregnancy outcomes.

Temporal frequency requirements for tissue velocity imaging of the fetal heart

OBJECTIVES

The high velocity and short duration of myocardial motion requires a high sampling rate to obtain adequate temporal resolution; this issue becomes even more important when taking into consideration the high fetal heart rate. In this study we have established optimal sampling requirements for assessing the duration of various cardiac cycle events and myocardial velocities of the fetal heart using color-coded tissue velocity imaging (TVI).

METHODS

Recordings from 30 fetuses were acquired at an initial frame rate of 180-273 frames/s. All TVI recordings were performed from an apical four-chamber view and stored as cineloops of five to 10 consecutive cardiac cycles for subsequent offline analysis using software enabling a reduction in frame rate. Different components of the myocardial velocity curve, obtained from the basal part of the ventricular septum, were measured at the initial frame rate and compared with their equivalents at gradually decreased frame rates.

RESULTS

As acquisition frame rate was reduced, there was a marked increase in deviation from the initial values, resulting in an underestimation of all systolic and diastolic velocities. For the measured durations, there was a clear tendency to underestimate isovolumetric contraction and relaxation, and a clear tendency to overestimate ventricular ejection and diastolic E-wave and A-wave. An acceptable ⩽ 5% deviation from the value obtained at the highest frame rate corresponded to measurements obtained at above 150-200 frames/s.

CONCLUSIONS

A high sampling rate of at least 200 frames/s is necessary for adequate reconstruction of TVI data for the fetal heart. Frame rates that are too low result in considerable loss of temporal and velocity information.

Analysis of Segmental and Global Function of the Fetal Heart Using Novel Automatic Functional Imaging

BACKGROUND

Functional assessment of the fetal heart has always been a challenge. Automatic functional imaging (AFI), a novel non-Doppler methodology based on 2-dimensional acoustic markers tracking, measures myocardial deformation regardless of angle of interrogation. Thus, we studied the validity of AFI in segmental and global assessment of myocardial function in the fetus.

METHODS

AFI-based myocardial deformation parameters including segmental tissue velocity, strain, and strain rate as well as biventricular global strain and strain rate were measured from raw scan-line data obtained from 28 normal fetuses (20-38, median 28 weeks of gestation). Interobserver and intraobserver variability was analyzed. AFI data were compared with analogous Doppler-derived tissue velocity imaging parameters measured in the same 28 fetuses.

RESULTS

AFI was feasible in 94% of the fetuses studied with high reproducibility. AFI-based tissue velocity (3.9 +/- 1 cm/s) was comparable with tissue velocity imaging-based velocity (4 +/- 1.6 cm/s) in the right ventricle and in the left ventricle (AFI velocity 3.3 +/- 0.6 vs tissue velocity imaging 3.1 +/- 0.9 cm/s). Strain rate obtained by these two methods was also similar. Biventricular global strain and strain rate measured 16 +/- 4% and 1.6 +/- .5 seconds(-1), respectively. Tissue velocity increased whereas segmental strain rate decreased throughout gestation. Strain remained unchanged. Global strain rate significantly decreased with gestational age (r = -0.7).

CONCLUSION

AFI, a novel non-Doppler methodology, allows fast and accurate quantification of segmental and global myocardial function in the fetus. AFI-based tissue velocity increases with gestational age whereas segmental and the new parameter global strain rate decrease throughout gestation.

A systematic review of the accuracy of first-trimester ultrasound examination for detecting major congenital heart disease

OBJECTIVE

To evaluate the accuracy of first-trimester ultrasound examination in detecting major congenital heart disease (CHD) using a systematic review of the literature.

METHODS

General bibliographic and specialist computerized databases along with manual searching of reference lists of primary and review articles were used to search for relevant citations. Studies were included if a first-trimester ultrasound scan was carried out to detect CHD that was subsequently verified by a reference standard. Data were extracted on study characteristics and quality, and 2 x 2 tables were constructed to calculate sensitivity and specificity.

RESULTS

Ten studies (involving 1243 patients) were suitable for inclusion. Of these, four used transabdominal ultrasonography, four used transvaginal and two used a combination. Pooled sensitivity and specificity were 85% (95% CI, 78-90%) and 99% (95% CI, 98-100%), respectively.

CONCLUSION

Ultrasound examination of the fetus in the first trimester is feasible for accurately detecting major CHD. It may be offered to women at high risk of having children with CHD.

Keeping abreast of advances in fetal cardiology

Advances in genetics and computing have contributed to a better understanding of the mechanisms underlying cardiovascular development, its programming and possible therapeutic manipulation. Pre-conceptual folate can reduce the prevalence of cardiac malformations and improvements in imaging allow us to detect congenital heart disease and assess function at earlier gestations. Three- and four-dimensional imaging may improve the surgeons' understanding of complex vascular malformations as well as permitting remote diagnosis. Treatment of fetal arrhythmias may be rationalised by fetal electrocardiography and magnetocardiography and by further defining the natural history of complete heart block and mechanisms of tachyarrhythmia. Tissue engineering and robotics may improve the surgical outcome for children by creating conduits with growth potential thus reducing the need for multiple surgical procedures. These technologies may permit successful fetal surgical procedures. Cross discipline collaboration has been key in enabling these advances which have changed the face of fetal cardiology.

Congenital cardiac malformations in relation to central venous access

During the third and seventh weeks of gestation, teratogenic exposure may lead to fetal abnormality such as congenital heart defects or intrauterine death. Congenital heart defects are present from birth, but may appear at any time, or only revealed postmortem. Often defects are present by degree. Some defects are life-threatening, while other, less severe conditions, may have minimal physiological impact. Left superior vena cava exists in early embryonic development, but the vessel degenerates as the cardiovascular system matures. When not associated with other malformations, an incidence of persistent left-sided superior vena cava (PLSVC) has no clinical signs or symptoms. However, it may not be as innocuous as it appears due to its association with the cyanotic defect, tetralogy of Fallot (TOF). Using a case history as an illustration it can be shown that all cases of defect or chromosomal suspicion should be documented as there may be implications for future interventions.

Early fetal echocardiography: heart biometry and visualization of cardiac structures between 10 and 15 weeks' gestation

OBJECTIVE

The purpose of this prospective cross-sectional study was to compile normative data about biometry of the fetal heart and great vessels between 10 and 15 weeks in 123 normal singleton pregnancies. Additionally, we investigated the different methods and the optimal examination time of early fetal echocardiography.

METHODS

The interrogated parameters included total heart diameter; heart area and circumference; right and left ventricular diameter; diameter, circumference, and area of the thorax; and diameter of the aorta and pulmonary trunk. Visualization of the 4-chamber view, 3-vessel view, origin and crossover of the great arteries, aortic arch, ductus arteriosus, superior and inferior venae cavae, and pulmonary veins was analyzed, and the success rates by transvaginal sonography (TVS) and transabdominal sonography (TAS) were calculated.

RESULTS

Complete evaluation of the fetal heart was impossible at 10 weeks; the total success rate increased from 45% at 11 weeks to 90% between 12 and 14 weeks and 100% at 15 weeks. Between 10 and 13 weeks, TVS was superior to TAS. At 14 weeks, both methods were similar to each other, and at 15 weeks, TAS allowed adequate visualization of all structures. Linear regression analysis showed a significant correlation between the interrogated parameters and gestational age, crown-rump length, and biparietal diameter (P < .05). The ratio of right and left ventricular diameters and the ratio of pulmonary trunk and aortic diameters were constant.

CONCLUSIONS

Early fetal heart evaluation by TVS or TAS or both is reasonable and feasible. Our normative data could be helpful for understanding the normal development of the fetal heart and great arteries and for detection of cardiac defects in early pregnancy.

New developments in fetal heart scanning: three- and four-dimensional fetal echocardiography

This article reviews the possibilities of three- and four-dimensional (3- and 4D) fetal echocardiography. A volume data set of a fetal heart can be acquired as a static volume, as a real-time 3D volume or as an offline 4D volume cine using spatial and temporal image correlation (STIC) software. STIC is explained and the potentials of this modality are emphasized. The display of a fetal heart volume data set demonstrates the cross-sections of interest, using the multiplanar mode or tomographic multislice imaging, and different volume rendering tools. The latter include: surface, minimum, inversion and glass body modes. This review highlights the potential of acquiring a digital volume data set of a heart cycle for later offline evaluation, either for an offline diagnosis, a second opinion (e.g. via Internet link) or for teaching fetal echocardiography to trainees and sonographers.