Impact of altered loading conditions on ventricular performance in fetuses with congenital cystic adenomatoid malformation and twin-twin transfusion syndrome

Cardiac adaptation and malformation in twin-twin transfusion syndrome and selective fetal growth restriction: A systematic review

OBJECTIVES

This systematic review explores cardiac adaptation in monochorionic (MC) twins with twin-twin transfusion syndrome (TTTS) or selective fetal growth restriction (sFGR) and assesses the risk of congenital heart defects (CHDs).

METHODS

Adhering to PRISMA guidelines, 63 studies were reviewed (49 on cardiac adaptation, 13 on CHD, one on both). A narrative synthesis of cardiac adaptation patterns was performed. Additionally, a meta-analysis compared the livebirth prevalence of CHD in TTTS and sFGR against uncomplicated MC twins.

RESULTS

In TTTS recipients, cardiac function may be impaired for diastolic, systolic, as well as global functions, while in donors, cardiac function is generally preserved. In sFGR, large twins may show hypertrophic cardiomyopathy, and small twins may show impaired systolic function. Co-occurrence of TTTS and sFGR magnifies cardiac impact but is often underreported. Meta-analysis for CHD prevalence revealed a relative risk ratio of 3.5 (95% CI: 2.5-4.9) for TTTS and 2.2 (95%CI: 1.3-3.5) for sFGR compared with uncomplicated MC twins.

CONCLUSIONS

This study highlights the well-documented cardiac adaptation in TTTS, contrasting with limited understanding in sFGR. Elevated CHD risks were observed in both conditions. Enhanced cardiovascular surveillance is warranted in complicated MC twin pregnancies. Future research should explore cardiac adaptation in sFGR and its long-term consequences.

Minute Stroke Distance Is a More Reproducible Measurement Than Cardiac Output in the Assessment of Fetal Ventricular Systolic Function

BACKGROUND

Echocardiographic quantification of fetal cardiac output (CO) aids clinical decision-making in the management of various cardiac and extracardiac diseases. Small variability in measuring semilunar valve dimension significantly reduces the reproducibility of the calculated CO. The authors propose minute stroke distance or velocity-time integral (VTI) as a more reproducible measure reflecting fetal ventricular systolic function. The aim of this study was to test the hypothesis that right and left ventricular minute VTI increase predictably with estimated fetal weight and are more reproducible than CO.

METHODS

Five hundred seventy-one singleton fetuses without cardiovascular pathology between 16 and 36 weeks' gestation were reviewed retrospectively. Twenty-two fetuses with pathology resulting in low- or high-CO states were also assessed for comparison. VTI was measured in both ventricular outflow tracts at the level of the semilunar valve, excluding a Doppler insonation angle of >30°. Heart rate, semilunar valve dimension, and VTI determined minute VTI and CO. Inter- and intrarater variability were evaluated in a random 10% subset.

RESULTS

Minute VTI and CO measurements were feasible in 67% to 89% of fetuses in this retrospective study. Minute VTI and CO increased with estimated fetal weight nonlinearly (R = 0.61-0.94). The mean inter- and intrarater variability for VTI, 6% and 5.7%, were significantly less than for CO, 25% and 23.7% (P < .001 for all).

CONCLUSIONS

Minute VTI is an easily measured, highly reproducible method of quantifying fetal ventricular systolic function. Variability in calculated CO from valve measurement differences is minimized by solely using VTI. Nomograms of minute VTI provide an efficient and precise assessment of fetal systolic function and may be used to track fetuses in disease states with low or high CO.

The heart after surviving twin-to-twin transfusion syndrome

BACKGROUND

The persistent changes in cardiac structure and function in children who survived twin-to-twin transfusion syndrome remain a matter of concern and controversy. Current fetal echocardiographic parameters and their postnatal evolution can help improve our understanding of the subject.

OBJECTIVE

To describe the echocardiographic changes of monochorionic fetuses affected by twin-to-twin transfusion syndrome, the recipient and the donor, before and after laser photocoagulation and to determine their evolution in the third trimester and during their first year of life.

STUDY DESIGN

An observational study was conducted including 55 uncomplicated monochorionic diamniotic twins and 78 pairs with twin-to-twin transfusion syndrome, 44 stage I-II and 34 stage III-IV, prospectively enrolled from 2015 until 2018. Comprehensive echocardiography was performed at 4 time periods: before laser photocoagulation, at 24 to 72 hours after surgery, at 28 to 30 weeks of gestation, and at 6 to 12 months after birth. Echocardiographic parameters were transformed to z-scores or indexed for heart area, estimated fetal weight, or body mass surface.

RESULTS

At diagnosis, recipients in all stages presented larger hearts (cardiothoracic ratio z-score: 2.77 [0.8] vs controls: -0.03 [0.5]; P<.001) and signs of ventricular hypertrophy (left end-diastolic ventricle wall thickness: 2.68 [0.7] vs controls -0.03 [0.7]; P<.001), along with systolic (cardiac index recipients: 317 [114] mL/min/kg vs controls: 400 [120] mL/min/kg, P<.001) and diastolic impairment (isovolumetric relaxation time z-score: 2.76 [0.6] vs controls: 0.05 [0.6]; P<.001). Donors presented smaller ventricular areas and diameters when compared with controls (left end-diastolic ventricle area z-score: -1.48 [1] vs 0.03 [0.9]; P<.001), along with decreased longitudinal motion (tricuspid annular plane systolic excursion z-score: -0.9 [1] vs controls -0.04 [1]; P<.001) and shorter ejection time z-score (-1.5 [0.7] vs controls: 0.0 [0.7]; P<.001). After surgery, an improvement in functional parameters was observed in both fetuses, whereas most morphometric changes prevailed in donors and recipients in the prenatal period. Postnatally, cardiac remodeling persisted in recipients (left relative wall thickness: 0.34 [0.02] vs controls: 0.30 [0.02]; P<.001), whereas donors mainly presented a decreased longitudinal motion in infancy (tricuspid annular plane systolic excursion z-score: -0.72 [0.7] vs controls: 0.23 [0.9]; P<.05).

CONCLUSION

Cardiac remodeling is present in both fetuses at the twin-to-twin transfusion syndrome diagnosis, whereas diastolic dysfunction is only significant in the recipient. Fetal therapy improves most echocardiographic parameters, although postnatally, the echocardiographic changes persist in both fetuses.

Normal reference ranges for fetal cardiac function: Assessed by modified Doppler myocardial performance index (Mod MPI) in the Egyptian population

AIM

To develop gestational age-based reference ranges for the modified Doppler myocardial performance index (Mod MPI) and to examine the maternal characteristics that affect this measurement.

METHODS

This was a cross-sectional study, comprised of 1021 healthy pregnancies between 20+0 to 35+6 weeks' gestation. They were all undergoing ultrasound examination in Cairo Fetal Medicine Unit (CAIFM) in Cairo University, Egypt from 1st April 2017 till 1st April 2019. Mod MPI was obtained used method described by Friedman et al. (2003). Median and SD models were fitted between Mod MPI and gestational age. The distributions of Mod MPI Z-scores were examined in relation to maternal characteristics RESULTS: The normal Mod MPI in second and third trimester (20 + 1 to 35 + 6 weeks' gestation) was 0.408 ± 0.08. Mod MPI was not affected by maternal age, body mass index (BMI) or parity (p value 0.5, 0.6 and 0.2 respectively).

CONCLUSION

This study established normal reference ranges for Mod MPI according to gestational age and generated a graph with 5th,10th, 90th and 95th centiles. Maternal characteristics as age, BMI or parity do not affect value of Mod MPI.

Prenatal sonographic markers of the outcome in fetuses with bronchopulmonary sequestration

PURPOSE

To evaluate the prenatal sonographic predictive markers of the outcome in fetuses with bronchopulmonary sequestration (BPS).

METHODS

BPS size and diameter of the feeding artery (FA) were measured prenatally and postnatally. Velocity of the FA and the left ventricular-modified myocardial performance index (LV mod-MPI) were also evaluated prenatally.

RESULTS

Forty-seven women were included in the study. Mean gestational age, mass size, diameter and velocity of the FA, and LV mod-MPI at prenatal diagnosis were 23.5 ± 2.2 weeks, 3.6 ± 8.3 cm, 2.3 ± 0.6 mm, 46.6 ± 15.4 cm/s, and 0.46 ± 0.06, respectively. Mean mass diameter and FA diameter measured on postnatal CT examinations were 3.8 ± 1.0 cm and 2.3 ± 0.7 mm, respectively. Five patients had respiratory symptoms after birth. Twenty children (43%) underwent or were scheduled to undergo mass excision, and the remaining 27 (57%) were doing well without any intervention. There was no neonatal death. LV mod-MPI at diagnosis, the FA diameter after birth and the serial change in the FA size were significantly associated with postnatal mass excision.

CONCLUSION

The FA diameter and LV mod-MPI may be additional markers for predicting whether fetuses with BPS should undergo mass excision in early childhood or conservative care.

In fetuses with congenital lung masses, decreased ventricular and atrioventricular valve dimensions are associated with lesion size and clinical outcome

INTRODUCTION

The clinical importance of mass effect from congenital lung masses on the fetal heart is unknown. We aimed to report cardiac measurements in fetuses with congenital lung masses and to correlate lung mass severity/size with cardiac dimensions and clinical outcomes.

METHODS

Cases were identified from our institutional database between 2009 and 2016. We recorded atrioventricular valve (AVVz) annulus dimensions and ventricular widths (VWz) converted into z scores, ratio of aortic to total cardiac output (AoCO), lesion side, and congenital pulmonary airway malformation volume ratio (CVR). Respiratory intervention (RI) was defined as intubation, extracorporeal membrane oxygenation (ECMO), or use of surgical intervention prior to discharge.

RESULTS

Fifty-two fetuses comprised the study cohort. Mean AVVz and VWz were below expected for gestational age. CVR correlated with ipsilateral AVVz (R_S = -.59, P < .001) and ipsilateral VWz (-0.59, P < .001). Lower AVVz and AoCO and higher CVR were associated with RI. No patient had significant structural heart disease identified postnatally.

CONCLUSION

In fetuses with left-sided lung masses, ipsilateral cardiac structures tend to be smaller, but in our cohort, there were no patients with structural heart disease. However, smaller left-sided structures may contribute to the need for RI that affects a portion of these fetuses.

Fetal cardiac findings and hemodynamic changes associated with severe lower urinary tract obstruction in utero

OBJECTIVES

To describe fetal echocardiographic findings associated with lower urinary tract obstruction (LUTO) and to compare anatomic and hemodynamic measurements between fetuses with LUTO and gestational age (GA)-matched controls, with an emphasis on quantitative indices of diastolic function and cardiac output.

METHODS

This was a retrospective cohort study of fetuses diagnosed with severe LUTO with giant bladder, which underwent at least one fetal echocardiogram at our center between January 2005 and June 2018. Fetuses with major congenital heart disease were excluded. Control fetuses did not have any structural or functional abnormalities and were GA-matched to the LUTO fetuses based on the time of the first fetal echocardiogram. Cardiac anatomy and hemodynamic measurements were compared between fetuses with LUTO and controls. In infants with LUTO, serial fetal and postnatal echocardiographic data were assessed, when available, and clinical outcomes were reviewed.

RESULTS

Twenty-six fetuses with LUTO and at least one fetal echocardiogram available were identified, one of which was excluded due to hypoplastic left heart syndrome, leaving 25 LUTO fetuses in the final cohort. The mean GA at the first fetal echocardiogram was 25.4 ± 5.1 weeks in the LUTO group and 25.3 ± 5.0 weeks in the control group. Common findings in fetuses with LUTO included cardiomegaly (40%), pericardial effusion (44%), right ventricular (RV) hypertrophy (64%) and left ventricular (LV) hypertrophy (48%). Compared with GA-matched controls, LUTO fetuses had lower ascending aorta Z-score (-0.10 ± 0.94 vs -0.93 ± 1.03; P = 0.02) and aortic isthmus Z-score (-0.14 ± 0.86 vs -1.62 ± 1.11; P < 0.001), shorter mitral valve inflow time indexed to cardiac cycle length (0.46 ± 0.04 vs 0.41 ± 0.06; P = 0.002), and worse (increased) LV myocardial performance index (0.39 ± 0.03 vs 0.44 ± 0.04; P < 0.001). In addition, the ratio of RV to LV cardiac index was higher in LUTO fetuses compared with controls (1.62 ± 0.13 vs 1.33 ± 0.11; P < 0.001). Of the 25 LUTO pregnancies, two were lost to follow-up, three underwent elective termination of pregnancy and three ended in intrauterine fetal demise. Four (16%) patients had mildly hypoplastic left-heart structures, comprising two with aortic arch hypoplasia and two with mitral and aortic stenosis.

CONCLUSION

In addition to presenting with cardiomegaly, pericardial effusion and ventricular hypertrophy, fetuses with LUTO demonstrate LV diastolic dysfunction and appear to redistribute cardiac output as compared to control fetuses, which may contribute to the development of left-heart hypoplasia. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Time Interval Measurements of the Ductus Venosus During the Early Second Trimester of Pregnancy: Reference Ranges and Clinical Application

OBJECTIVES

The aims of this study were to construct reference ranges for the time interval parameters of the ductus venosus during the early second trimester of pregnancy and to demonstrate the clinical utility in various fetal disorders.

METHODS

The ductus venosus Doppler measurements of 331 healthy fetuses between 15 and 22 weeks' gestation were analyzed. The systolic time and diastolic time were subdivided into the systolic acceleration time, systolic deceleration time, diastolic acceleration time, and diastolic deceleration time. The median, 5th, and 95th regression lines for each variable were determined according to gestational age. The ductus venosus time interval parameters in cases of fetoplacental abnormalities were calculated and plotted against the reference ranges.

RESULTS

With advancing gestation, the systolic acceleration time and total systolic time increased significantly (P < .001). In contrast to the systolic phase, the diastolic deceleration time decreased significantly during the early second trimester of pregnancy (P = .023). The systolic deceleration time, diastolic acceleration time, and diastolic time were relatively constant. Fetuses with tricuspid insufficiency, twin-twin transfusion syndrome, intrauterine fetal growth restriction, and anemia had abnormal ductus venosus times with different patterns.

CONCLUSIONS

Predicted normal reference ranges for time interval variables in relation to gestational age were established. These could be helpful for assessing fetal cardiovascular function during the early second trimester of pregnancy.

Differential Changes in Myocardial Performance Index and Its Time Intervals in Donors and Recipients of Twin-to-Twin Transfusion Syndrome before and after Laser Therapy

OBJECTIVE

To evaluate left myocardial performance index (MPI) and time intervals in fetuses with twin-to-twin transfusion syndrome (TTTS) before and after laser surgery.

METHODS

Fifty-one fetal pairs with TTTS and 47 uncomplicated monochorionic twin pairs were included. Left ventricular isovolumetric contraction time (ICT), ejection time (ET), and isovolumetric relaxation time (IRT) were measured using conventional Doppler.

RESULTS

Recipients showed prolonged ICT (46 ± 12 vs. 31 ± 8 vs. 30 ± 5 ms; p < 0.001) and IRT (51 ± 9 vs. 43 ± 8 vs. 43 ± 5 ms; p < 0.001) and higher MPI (0.57 ± 0.12 vs. 0.47 ± 0.09 vs. 0.44 ± 0.05; p < 0.001) than donors and controls. Donors showed shorter ET than recipients and controls (157 ± 12 vs. 169 ± 10 vs. 168 ± 10 ms; p < 0.001) and higher MPI than controls (0.47 ± 0.09 vs. 0.44 ± 0.05; p = 0.006). Preoperative MPI changes were observed in all TTTS stages. Time intervals partially improved after surgery.

CONCLUSION

Donor and recipient twins had higher MPI due to different changes in the time intervals, possibly reflecting the state of hypovolemia in the donor and hypervolemia and pressure overload in the recipient.

Novel Technique for Measurement of Fetal Right Myocardial Performance Index Using Dual Gate Pulsed-Wave Doppler

OBJECTIVES

To evaluate the reproducibility of the fetal right myocardial performance index determined by simultaneous recording of inflow and outflow using a dual gate pulsed-wave Doppler (DD).

METHODS

This was a prospective study of 39 normal singleton fetuses. Two experienced operators each measured the right myocardial performance index in three ways, twice: (1) separate recording of the inflow and outflow using single-gate pulsed-wave Doppler (PD), (2) simultaneous recordings of the inflow and outflow using tissue Doppler (TD), and (3) simultaneous recordings of the inflow and outflow using DD. Intra- and interoperator reproducibility were assessed with intraclass correlation coefficients. The measurements from all three methods taken by the more experienced operator were compared using Bland-Altman plots and mean differences.

RESULTS

For both operators, intra-operator reproducibility was the highest when using DD, followed by PD, and TD. Interoperator agreement was the highest for PD measurements, followed by DD, and TD. The smallest mean difference was between the PD and DD measurements by the more experienced operator. There was a positive correlation between PD and DD values (r = 0.369, P < .001).

CONCLUSIONS

Dual gate pulsed-wave Doppler may be an effective alternative to the PD or TD methods, and can separately evaluate systolic and diastolic myocardial function.

Evaluation of right ventricular function in fetal hypoplastic left heart syndrome by color tissue Doppler imaging

OBJECTIVE

Postnatal outcome of fetuses with hypoplastic left heart syndrome (HLHS) is determined mainly by right ventricular function. Our study examines whether there are differences in right ventricular function during gestation of fetuses with HLHS compared with healthy fetuses.

METHODS

A prospective study was conducted including 20 fetuses with HLHS and 20 gestational age-matched controls. Peak systolic and diastolic right ventricular free wall velocities were assessed using color tissue Doppler imaging (c-TDI). Subsequently, isovolumic time intervals, ejection time (ET'), E'/A' ratio and tissue Doppler-derived myocardial performance index (MPI') were calculated. Possible changes to c-TDI indices during the course of pregnancy in both the HLHS group and the control group were investigated.

RESULTS

Examination of right ventricular function revealed significantly lower E' velocities (13.6 vs 21.0 cm/s; P = 0.017) and E'/A' ratios (0.55 vs 0.76; P = 0.012) and prolonged isovolumic contraction time (ICT') (57.0 vs 45.7 ms; P = 0.008) in the HLHS group compared with healthy fetuses. Furthermore, isovolumic relaxation time and MPI' increased significantly with gestational age in HLHS fetuses but not in controls. Values for systolic and diastolic peak velocities (E', A', S'), ET' and ICT' did not change significantly during gestation in either group.

CONCLUSION

Right ventricular function in HLHS is altered as early as in fetal life, well before palliative surgery is performed. Future research should provide further insight into ventricular remodeling during gestation in cases of HLHS. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Mass Effect Alone May Not Explain Pulmonary Vascular Pathology in Severe Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) and congenital pulmonary airway malformation (CPAM) are diseases in which chest-occupying lesions can result in severe pulmonary hypoplasia. However, significant postnatal mortality due to pulmonary hypertension (PH) is more often seen in patients with CDH. We analyzed prenatal echocardiographic parameters of pulmonary vascular pathology in these groups to understand whether PH in patients with CDH is secondary to a mass effect or to underlying disease. We analyzed pre- and postnatal characteristics of 26 patients with severe CDH and 23 patients with severe CPAM from 2009 to 2012. Severe mediastinal compression, indicated by a low cardiothoracic ratio, was evident in both groups. However, fetuses with severe CDH had smaller pulmonary arteries bilaterally and higher pulsatility indices in the ipsilateral lung than those with severe CPAM. Prenatal modified McGoon indices were significantly lower in patients with CDH versus CPAM. Consistent with these prenatal measurements, postnatal PH was seen more frequently in patients with CDH compared to CPAM. Patients with severe CDH have prenatal evidence of pulmonary vascular remodeling compared to patients with severe CPAM. These results suggest a multifactorial origin for PH in CDH and support the idea of using prenatal medical therapies to promote vascular remodeling in these patients.

Longitudinal annular displacement by M-mode (MAPSE and TAPSE) in twin-to-twin transfusion syndrome before and after laser surgery

OBJECTIVE

To evaluate mitral and tricuspid annular plane systolic excursion (MAPSE and TAPSE) in fetuses with twin-to-twin transfusion syndrome (TTTS) before and after laser therapy.

METHODS

A prospective study in 24 fetal pairs with TTTS evaluated 24 h before and within 48 h after fetoscopy and 13 gestational age-matched normal monochorionic fetal pairs. MAPSE and TAPSE were measured in an apical or basal four-chamber view by placing the M-mode cursor at the lateral valve ring.

RESULTS

Mean preoperative MAPSE (controls 3.6 ± 1.3 mm vs. donors 2.7 ± 0.8 mm vs. recipients 2.8 mm ± 0.9; P < 0.001) and TAPSE (controls 4.4 ± 1.5 mm vs. donors 3.3 ± 1 mm vs. recipients 3.6  ± 1.1 mm; P < 0.001) values were significantly reduced in both TTTS fetuses. When subdividing according to TTTS stages, changes were significant in both stage I-II and III-IV subgroups, although differences were more pronounced in the latter. All observations remained unchanged 48 h post-fetoscopy.

CONCLUSION

Both recipient and donor fetuses had decreased global longitudinal motion, even in early TTTS stages.

The Fetal Modified Myocardial Performance Index: Is Automation the Future?

The fetal modified myocardial performance index (Mod-MPI) is a noninvasive, pulsed-wave Doppler-derived measure of global myocardial function. This review assesses the progress in technical refinements of its measurement and the potential for automation to be the crucial next step. The Mod-MPI is a ratio of isovolumetric to ejection time cardiac time intervals, and the potential for the left ventricular Mod-MPI as a tool to clinically assess fetal cardiac function is well-established. However, there are wide variations in published reference ranges, as (1) a standardised method of selecting cardiac time intervals used in Mod-MPI calculation has not been established; (2) cardiac time interval measurement currently requires manual, inherently subjective placement of callipers on Doppler ultrasound waveforms; and (3) ultrasound machine settings and ultrasound system type have been found to affect Mod-MPI measurement. Collectively these factors create potential for significant inter- and intraobserver measurement variability. Automated measurement of the Mod-MPI may be the next key development which propels the Mod-MPI into routine clinical use. A novel automated system of Mod-MPI measurement is briefly presented and its implications for the future of the Mod-MPI in fetal cardiology are discussed.

Evaluation of right ventricular function in fetuses with hypoplastic left heart syndrome using tissue Doppler techniques

OBJECTIVE

The outcome of patients with hypoplastic left heart syndrome (HLHS) is influenced by right ventricular function. This study aimed to investigate whether differences in right ventricular function of fetuses with HLHS are present during gestation.

METHODS

This was a prospective study comprising 14 fetuses with HLHS (28 measurements obtained in total) and 28 normal control fetuses (31 measurements obtained in total). The two groups were matched for gestational age. Ultrasound M-mode was used to assess displacement of the tricuspid annulus. Spectral Doppler and myocardial tissue Doppler-derived inflow and outflow velocities were assessed. Tricuspid valve peak early wave to peak active wave (E/A) ratio, the early wave to early diastolic annular relaxation velocity (E/E') ratio and the tissue Doppler-derived myocardial performance index (MPI') were calculated.

RESULTS

E-wave velocity was significantly higher in fetuses with HLHS than in control fetuses (mean, 40.14 cm/s vs 35.47 cm/s; P < 0.05, respectively), and A-wave velocity in fetuses with HLHS showed a tendency for higher values in the right ventricle compared with normal control fetuses, but this did not reach statistical significance (61.16 cm/s vs 54.64 cm/s; P = 0.08). The E/A ratio increased during gestation in controls, but this increase was not seen in HLHS fetuses. Peak annular velocity during atrial contraction (A') and the E/E' ratio were significantly lower in controls than in HLHS fetuses: 9.50 cm/s vs 10.39 cm/s (P < 0.05) and 5.77 vs 7.37 (P < 0.05), respectively. There were no differences for right-ventricular MPI' or tricuspid annular plane systolic excursion between HLHS fetuses and controls.

CONCLUSION

The results of this study show that altered right ventricular function in HLHS infants may develop antenatally. It is hoped that confirmation of these findings using Doppler-independent techniques will lead to further exploration of ventricular function in HLHS fetuses. Consequently, parental counseling and postnatal management strategies could be influenced.

Is There a Measurable Difference between the Left and Right Modified Myocardial Performance Indices, and Does This Change to Reflect Unilateral Myocardial Dysfunction in Pathology?

Introduction: Fetal cardiac dysfunction may manifest itself unilaterally as right and left ventricles differing in design, function and load, measurable as differing in myocardial performance indices (MPIs). We wished to define this difference (‘delta-MPI' or DMPI), present its normal range and pilot its use in pathological pregnancy. Material and Methods: Prospective cross-sectional study of 324 normal singleton fetuses (16-38 weeks of gestation). Left and right modified MPI (LMPI and RMPI) were performed during a single examination using the ‘peak' valve click technique. Thirty-seven pathological singleton and monochorionic diamniotic twin pregnancies were compared as pilot data. Results: Modified MPIs (mean ± SD) were 0.45 ± 0.06 (LMPI) and 0.47 ± 0.09 (RMPI), being similar at 18 weeks' gestation with DMPI increasing slightly throughout pregnancy (0.02 ± 0.08). Both singleton intrauterine growth restriction (IUGR) and recipient twin-twin transfusion syndrome (TTTS) showed significantly elevated RMPI, LMPI and DMPI, most pronounced for DMPI (450 and 500% increase, respectively; p < 0.01). DMPI acquisition rates were 83.3% normal and 87.0% pathological. Discussion: We demonstrate for the first time differing intrafetal LMPI and RMPI in a large gestational cohort, with this difference increasing with gestational age. Pilot data confirm the potential for DMPI as a tool to assess unilateral myocardial function in singleton IUGR and recipient twins in TTTS, and further studies are under way to evaluate its clinical utility.

The (Pulsed-Wave) Doppler Fetal Myocardial Performance Index: Technical Challenges, Clinical Applications and Future Research

Functional cardiovascular assessment is becoming an increasingly important tool in the study of fetal pathology. The myocardial performance index (MPI) is a parameter measuring global myocardial function. Since its introduction, several studies have proposed methods to improve its reproducibility and have constructed normative reference ranges. Fetal heart evaluation using the MPI is technically challenging, requiring specific training and expertise, and a consensus has yet to be reached on the method of delineating the time periods used to calculate the index. Despite these limitations, it has been shown to be a useful and highly sensitive parameter of dysfunction in a number of fetal pathologies. Further research is warranted into the effect of pathology on MPI, parameters of unilateral cardiac strain that utilise MPI, and automation of the MPI to encourage incorporation of the MPI as a useful tool in clinical practice.

Diagnosis and treatment of fetal cardiac disease: a scientific statement from the American Heart Association

BACKGROUND

The goal of this statement is to review available literature and to put forth a scientific statement on the current practice of fetal cardiac medicine, including the diagnosis and management of fetal cardiovascular disease.

METHODS AND RESULTS

A writing group appointed by the American Heart Association reviewed the available literature pertaining to topics relevant to fetal cardiac medicine, including the diagnosis of congenital heart disease and arrhythmias, assessment of cardiac function and the cardiovascular system, and available treatment options. The American College of Cardiology/American Heart Association classification of recommendations and level of evidence for practice guidelines were applied to the current practice of fetal cardiac medicine. Recommendations relating to the specifics of fetal diagnosis, including the timing of referral for study, indications for referral, and experience suggested for performance and interpretation of studies, are presented. The components of a fetal echocardiogram are described in detail, including descriptions of the assessment of cardiac anatomy, cardiac function, and rhythm. Complementary modalities for fetal cardiac assessment are reviewed, including the use of advanced ultrasound techniques, fetal magnetic resonance imaging, and fetal magnetocardiography and electrocardiography for rhythm assessment. Models for parental counseling and a discussion of parental stress and depression assessments are reviewed. Available fetal therapies, including medical management for arrhythmias or heart failure and closed or open intervention for diseases affecting the cardiovascular system such as twin-twin transfusion syndrome, lung masses, and vascular tumors, are highlighted. Catheter-based intervention strategies to prevent the progression of disease in utero are also discussed. Recommendations for delivery planning strategies for fetuses with congenital heart disease including models based on classification of disease severity and delivery room treatment will be highlighted. Outcome assessment is reviewed to show the benefit of prenatal diagnosis and management as they affect outcome for babies with congenital heart disease.

CONCLUSIONS

Fetal cardiac medicine has evolved considerably over the past 2 decades, predominantly in response to advances in imaging technology and innovations in therapies. The diagnosis of cardiac disease in the fetus is mostly made with ultrasound; however, new technologies, including 3- and 4-dimensional echocardiography, magnetic resonance imaging, and fetal electrocardiography and magnetocardiography, are available. Medical and interventional treatments for select diseases and strategies for delivery room care enable stabilization of high-risk fetuses and contribute to improved outcomes. This statement highlights what is currently known and recommended on the basis of evidence and experience in the rapidly advancing and highly specialized field of fetal cardiac care.

Right ventricular mechanics in the fetus with hypoplastic left heart syndrome

BACKGROUND

Right ventricular mechanics influence outcomes in patients with hypoplastic left heart syndrome (HLHS). The aim of this study was to determine whether differences in right ventricular performance have their origins in fetal life and if the architectural character of the hypoplastic left ventricle affects right ventricular mechanics.

METHODS

The first complete fetal echocardiograms after 17 weeks' gestation were reviewed in 84 fetuses with HLHS and in 115 gestational age-matched normal controls. Inflow, outflow, and myocardial tissue Doppler velocities were measured. E/A and E/e' ratios and right ventricular myocardial performance index were calculated.

RESULTS

In fetuses with HLHS, there were lower tricuspid E/A ratios (mean, 0.6 ± 0.1 vs 0.7 ± 0.1; P < .001), higher E/e' ratios (mean, 8.1 ± 2.6 vs 7.0 ± 1.3; P = .006), and higher right ventricular myocardial performance indices (mean, 0.47 ± 0.14 vs 0.40 ± 0.10; P < .001) compared with controls. Among fetuses with HLHS grouped according to left ventricular architecture, those with left ventricular endocardial fibroelastosis had the most striking differences in right ventricular mechanics.

CONCLUSIONS

Right ventricular mechanics are different from normal in fetuses with HLHS and are influenced by the presence of left ventricular endocardial fibroelastosis. These differences precede the imposition of undue loading conditions as a consequence of surgical palliation and may offer clues to the development of later right ventricular failure.

Tissue Doppler-derived measurement of isovolumic myocardial contraction in the pediatric population

Multiple echocardiographic techniques have been utilized to quantify systolic function. The shortening and ejection fraction remain the most commonly used and accepted methods. However, these measures are affected by altered loading conditions, and are not applicable when ventricular geometry differs from the prolate ellipsoid typical of a left ventricle. Mitral valve annular acceleration during isovolumic contraction (IVA) has been proposed as a load independent index of left ventricular contractility. However, published values for IVA demonstrating normal function vary. In addition, the value of IVA which may discern impaired systolic function has not been established. The purpose of this study is to determine a threshold IVA value for abnormal left ventricular function in the pediatric population. Structurally/functionally normal control (n = 90) and dilated cardiomyopathy (study = 64) patients were compared for differences in left ventricular: wall stress (WS), velocity of circumferential fiber shortening (VCFc), ejection fraction (EF), ejection force, and pulsed wave-derived medial and lateral wall IVA. No difference in body surface area (p = 0.61) or gender (p = 0.53) was noted. Left ventricular ejection fraction, ejection force, VCFc, and IVA were significantly lower and WS was significantly higher in the study group (p < 0.01). The medial IVA was 1.71 ± 0.89 m/s(2) for an EF <40%, 1.74 ± 0.70 m/s(2) for an EF = 40-50%, 2.46 ± 0.89 m/s(2) for an EF >50%. The lateral IVA was 1.81 ± 1.03 m/s(2) for an EF <40%, 2.07 ± 0.78 m/s(2) for an EF = 40-50%, 2.54 ± 0.99 m/s(2) for an EF >50%. ROC analysis demonstrated a medial IVA of 1.97 m/s(2) as the cut-off for predicting an EF <50% with a 77% sensitivity of and specificity of 66% (AUC = 0.75, CI = 0.67-0.83, p < 0.01). ROC analysis demonstrated a lateral IVA of 2.31 m/s(2) as the cut-off for predicting an EF <50% with a 73% sensitivity of and specificity of 63% (AUC = 0.72, CI = 0.63-0.82, p < 0.01). IVA lateral of 1.93 m/s(2) or less was associated with heart transplant and death. ICC analysis demonstrated some interobserver variability in IVA measurement (0.57-0.65). The normal IVA of the medial and lateral mitral valve annulus measure over 1.97 m/s(2) and 2.31 m/s(2), respectively; values less than this cut-off are associated with EF <50%. Despite some problems with reproducibility IVA remains a promising method of screening for diminished ventricular contractility in the setting of abnormal geometry.

Reproducibility of constituent time intervals of right and left fetal modified myocardial performance indices on pulsed Doppler echocardiography: a short report

OBJECTIVE

To assess reproducibility of constituent time intervals measured by pulsed Doppler echocardiography for calculation of the right and left fetal myocardial performance indices (MPIs).

METHODS

This was a prospective study of 30 normal singleton pregnancies (19-36 weeks). In each, five different time intervals were measured from the Doppler waveform and four repeated measures were taken for each time interval. Three were from the left heart: isovolumetric contraction time (ICT), isovolumetric relaxation time (IRT) and ejection time (ET); two were from the right heart: 'a-interval' and 'b-interval'. The left and right modified MPIs (Mod-MPIs) generated by these constituent time intervals were also evaluated. Two operators evaluated the reproducibility of all measures.

RESULTS

There was generally good intra- and interobserver reproducibility for all time intervals and resultant Mod-MPIs: ICT, range, 19-43 ms with intraclass correlation coefficient (ICC), 0.91 (95% CI, 0.85-0.95); ET, range, 160-184.8 ms with ICC, 0.90 (95% CI, 0.84-0.95); IRT, range, 35.8-48.5 ms with ICC, 0.67 (95% CI, 0.52-0.81); a-interval, range 208-265 ms with ICC, 0.89 (95% CI, 0.82-0.94); b-interval, range, 163.1-188.3 ms with ICC, 0.82 (95% CI, 0.71-0.90); left Mod-MPI, range, 0.33-0.48 with ICC, 0.84 (95% CI, 0.74-0.91); right Mod-MPI, range, 0.21-0.49 with ICC, 0.82 (95% CI, 0.71-0.90). The 95% limits of agreement showed no statistically significant difference in measurements between the two examiners for all time intervals.

CONCLUSION

This is the first study to evaluate the reproducibility of the component time intervals of both right and left fetal Mod-MPIs in the second and third trimesters and supports the reproducibility of fetal functional cardiac assessment. The IRT is the main source of variation for the left Mod-MPI so should be the focus of further investigation. Even using two separate pulsed-wave Doppler gates and therefore separate cardiac cycles, the right Mod-MPI is reproducible.

Twin-twin transfusion syndrome

Twin-twin transfusion syndrome (TTTS) is a serious condition that affects 10% to 15% of twin pregnancies with monochorionic diamniotic placentation. The pathophysiology of TTTS is not completely understood; however, the presence of unbalanced placental vascular communications within a shared circulation has been implicated in its development. The presentation of TTTS is highly variable, and it does not always progress in a predictable manner. Monochorionic twin gestations should, therefore, be monitored for signs of TTTS with serial sonograms starting in the second trimester. Early TTTS can be managed conservatively. However, without intervention, early-onset advanced TTTS is associated with a high perinatal loss rate and risk of severe neurologic impairment among survivors. Limited studies suggest that fetoscopic laser photocoagulation is the best available treatment for advanced TTTS diagnosed in the second trimester. Even with laser therapy, there remains a significant risk of twin demise and neurologic handicap in survivors.

Fetal cardiac function: technical considerations and potential research and clinical applications

Fetal echocardiography was initially used to detect structural anomalies but has more recently also been proposed to assess fetal cardiac function. This review summarizes technical issues and limitations in fetal cardiac function evaluation, as well as its potential research and clinical applications. Functional echocardiography has been demonstrated to select high-risk populations and to be associated with outcome in several fetal conditions including intrauterine growth restriction, twin-to-twin transfusion syndrome, maternal diabetes, and congenital diaphragmatic hernia. Fetal heart evaluation is challenging due to the smallness and high heart rate of the fetus and restricted access to the fetus far from the transducer. Due to these limitations and differences in cardiac function which are related to fetal maturation, cardiovascular parameters should be validated in the fetus and used with caution. Despite these precautions, in expert hands and with appropriate ultrasound equipment, evaluation of cardiac function is feasible in most fetuses. Functional fetal echocardiography is a promising tool that may soon be incorporated into clinical practice. Research is warranted to further refine the contribution of fetal cardiac assessment to the diagnosis, monitoring, or prediction of outcomes in various fetal conditions.

Fetal left modified myocardial performance index: technical refinements in obtaining pulsed-Doppler waveforms

OBJECTIVE

To assess the influence of machine settings (wall motion filter (WMF), angle of insonation, Doppler aliasing) and phase of valve clicks on repeatability of measurement of the fetal left modified myocardial performance index (Mod-MPI).

METHODS

Fetal left Mod-MPI was evaluated prospectively in 157 morphologically normal fetuses at 19-36 weeks' gestation. In a baseline cohort, a previously published technique and settings were used for measurement of Mod-MPI. In a second cohort, the influence of WMF, angle of insonation, Doppler aliasing and selection of the phase of the valve clicks on repeatability of measurement of Mod-MPI was assessed.

RESULTS

The intraclass correlation coefficient (ICC) for measurement repeatability in the baseline cohort was 0.22. Increase in WMF to 300 Hz or 500 Hz was associated with an increase in ICC to 0.60 and 0.55, respectively. An angle of insonation of < 15° was associated with an increase in ICC to 0.79 and 0.78 at a WMF of 300 and 500 Hz, respectively. A WMF of 300 Hz, angle of insonation of < 15° and absence of aliasing was associated with an increase in ICC to 0.85 and 0.87 at the beginning and peak of the valve click, respectively. Mod-MPI ranged from 0.35 to 0.48. An increase in calculated MPI was associated with increasing WMF, selection of the beginning vs. peak of the valve clicks and increase in angle of insonation. The presence or absence of aliasing had no effect.

CONCLUSIONS

Refinement of machine settings improves repeatability of Mod-MPI, as does selection of the peak of the valve click. We suggest a consensus be reached as to the precise measurement of MPI, but for the moment would suggest: WMF, 300 Hz; angle of insonation, < 15°; avoiding Doppler aliasing; and selection of valve click peak. Systematic variation in measurement of time intervals may be responsible for the widely varying published normal ranges for Mod-MPI.

Fetal cardiovascular effects of lower urinary tract obstruction with giant bladder

OBJECTIVE

Lower urinary tract obstruction (LUTO) with massive bladder distension impacts on a variety of developing organ systems with consequent morbidity and mortality. The impact of LUTO on the fetal cardiovascular system has not previously been investigated. We hypothesize that a giant, distended bladder within the pelvis may cause vascular compression with observable consequences.

METHODS

Fetal echocardiography was performed in 42 fetuses with LUTO and compared with 35 normal controls matched for gestational age. Parameters investigated included cardiothoracic ratio, presence or absence of ventricular hypertrophy and pericardial effusion. Doppler echocardiographic examination of mitral and tricuspid valve inflow and the ductus venosus was performed. To assess arterial vascular impedance, pulsatility indices (PIs) were calculated for segments of the descending aorta and right and left iliac arteries (RIA and LIA).

RESULTS

In the LUTO group an increased cardiothoracic ratio was seen in nine (21%), ventricular hypertrophy in 12 (29%) and small pericardial effusion in 15 (36%). Filling characteristics of the right ventricle in the LUTO group demonstrated greater dependency upon atrial contraction, and ductus venosus flow demonstrated higher downstream impedance to filling, than in controls, suggesting altered compliance. The LUTO group also had lower distal descending aorta PI (1.53 ± 0.38 vs. 1.76 ± 0.44, P = 0.04), lower RIA-PI (1.31 ± 0.29 vs. 1.76 ± 0.44, P < 0.001) and lower LIA-PI (1.41 ± 0.44 vs. 1.73 ± 0.31, P < 0.01) than controls, suggesting vascular compression and increased impedance to flow.

CONCLUSIONS

LUTO with giant urinary bladder compresses the iliac arteries, which may lead to increased afterload. Further study is warranted to examine the impact of fetal treatment such as bladder drainage on these cardiovascular parameters.

The Fetal Heart in Twin-to-Twin Transfusion Syndrome

Twin-to-twin transfusion syndrome is a severe complication occurring in 10% of monochorionic twin pregnancies. The disease is usually explained as due to an intrauterine imbalance in intertwin blood exchange, which leads to a volume depleted-donor twin and an overfilled recipient twin. The recipient has signs of cardiac dysfunction, which can be measured using echocardiography or blood and amniotic fluid derived biomarkers. Whereas cardiac dysfunction typically progresses in pregnancies treated with amniodrainage, it usually disappears within a few weeks after fetoscopic laser coagulation of the connecting intertwin anastomoses. Nevertheless, recipients remain at a increased risk of pulmonary stenosis. In this paper, we summarize the cardiac alterations in twin-to-twin transfusion syndrome, describe the changes seen after fetal therapy, list the newly proposed staging systems based on fetal cardiac function, and make recommendations about the use of fetal echocardiography in the evaluation and followup of pregnancies complicated by twin-to-twin transfusion syndrome.

Tei index to assess fetal cardiac performance in fetuses at risk for fetal inflammatory response syndrome

OBJECTIVES

To examine, in patients with premature rupture of the amniotic membranes (PROM) at < 34 weeks of gestation, the relationship between fetal myocardial performance measured by the Tei index and fetal inflammatory response syndrome (FIRS).

METHODS

A case-control study was conducted including 15 preterm PROM patients with gestational age between 24 and 33 weeks admitted to Hospital de Clínicas de Porto Alegre, and 15 controls with the same gestational age range. Fetal echocardiography with Doppler was performed at admission for the preterm PROM group, with serial examinations every 7-10 days thereafter until delivery, and at the time of inclusion in the control group. Flow velocity waveforms were obtained for the left ventricle, from which the Tei index was calculated. Placental histopathology and perinatal outcome were compared between the groups.

RESULTS

The left ventricular Tei index was significantly greater in fetuses with preterm PROM compared with controls (0.63 +/- 0.13 vs. 0.51 +/- 0.10, P = 0.007). While there was no difference in isovolumetric times, the left ventricular ejection time was significantly shorter in the preterm PROM group (164 +/- 17 ms vs. 184 +/- 16 ms, P = 0.003). In the preterm PROM group, neonatal sepsis was diagnosed in 73.3%, and funisitis and chorionic vasculitis confirmed FIRS in 53.3%, compared with 6.7% for these three diagnoses in controls (P = 0.001).

CONCLUSIONS

These data provide further evidence that cardiac dysfunction is present in the setting of preterm PROM. The study of myocardial performance with the Tei index is a novel non-invasive approach to assess cardiac function and monitor the fetus affected with FIRS.

The role of fetal echocardiography in fetal intervention: a symbiotic relationship

In this review, the authors explore the role of noninvasive and invasive fetal interventions in fetal cardiovascular disease guided by observations at fetal echocardiography. They first review fetal cardiac lesions that may be ameliorated by fetal intervention and then review noncardiac fetal pathologic findings for which fetal echocardiography can provide important insight into the pathophysiology and aid in patient selection for and timing of intervention and postintervention surveillance.

Assessment of fetal cardiac function before and after therapy for twin-to-twin transfusion syndrome

OBJECTIVE

We sought to assess fetal cardiac function in monochorionic twins before and after therapy for twin-to-twin transfusion syndrome (TTTS) and compare it with control subjects.

STUDY DESIGN

We conducted prospective longitudinal assessment of fetal cardiac function in cases undergoing curative fetal therapy for TTTS (n = 39) until 4 weeks postoperatively and in uncomplicated monochorionic twins (n = 23). Fetal cardiac function was assessed by the left and right ventricular myocardial performance index, atrioventricular valve flow pattern, ductus venosus a-wave, and umbilical vein pulsations.

RESULTS

Nomograms for the myocardial performance index were constructed. Fetal cardiac function was grossly abnormal in recipient twins of TTTS when compared with control subjects (P < .001 for all indices) but normalized by 4 weeks postoperatively. The donor developed abnormal ductus venosus flow and tricuspid regurgitation postoperatively that regressed within 4 weeks.

CONCLUSION

The cardiac dysfunction in the recipient twin of TTTS normalizes within 1 month after laser. The donor develops a transient impairment of cardiac function postoperatively.

Fetal cardiac output in monochorionic twins

OBJECTIVES

To compare fetal cardiac output (CO) in donor and recipient twins of twin-twin transfusion syndrome (TTTS) pregnancies after laser therapy with that of monochorionic twins without TTTS and normal singletons.

METHODS

In a longitudinal, prospective study, we sonographically assessed fetal CO in donors (n = 10) and recipients (n = 10) with TTTS after fetoscopic laser therapy, in monochorionic twins without TTTS (n = 20) and in normal singleton pregnancies (n = 20). The fetal CO of TTTS twins was determined 1 day and 1 week after laser treatment, and from then on every 2-4 weeks until birth. Twins without TTTS were examined biweekly until birth. Singletons were examined twice, with an 8-week interval, at different gestational ages between 17 and 35 weeks.

RESULTS

Absolute CO increased exponentially with advancing gestational age (P < 0.0001), and was significantly related to fetal weight in all groups (P < 0.0001). The median CO/kg in donors after laser therapy, recipients after laser therapy and non-TTTS monochorionic twins was significantly higher than that in singletons (all P < 0.001). Median CO/kg in donors after laser therapy, recipients after laser therapy, and non-TTTS monochorionic twins was not significantly different between groups.

CONCLUSIONS

Monochorionic twins with TTTS have higher CO after laser therapy than normal singletons.