Development of Australian reference ranges for the left fetal modified myocardial performance index and the influence of caliper location on time interval measurement

Feasibility of automated measurement of fetal right ventricular modified myocardial performance index with development of reference values and clinical application

To establish normal reference ranges for fetal right ventricular modified myocardial performance index (RV Mod-MPI) using automatic synchronization of the RV inflow and outflow images (MPI+TM). Additionally, we aimed to clinically apply RV Mod-MPI to investigate its changes in fetal right congenital diaphragmatic hernia (CDH) compared to normal fetuses. This prospective study included uncomplicated singleton pregnancies between 16 and 38 weeks of gestational age. Cases with any maternal or fetal complications that developed during the enrollment period were excluded. Two experienced operators measured the RV Mod-MPI using the automated and manual methods. The intraclass correlation coefficients (ICC) were calculated for intra- and inter-operator reproducibility. The mean differences between the manual and automated measurements were also compared. The RV Mod-MPI was then compared between the right CDH fetuses and normal fetuses. Seventy normal fetuses were analyzed for the feasibility of an automated system, and 364 examinations from 272 fetuses were analyzed for developing the normal references. The automated system showed significantly higher intra- and inter-operator reproducibility of Mod-MPI than those of manual measurements (ICC = 0.962 vs. 0.913 and 0.961 vs. 0.889, respectively). The mean difference in Mod-MPI between the manual and automated method was 0.0002 ± 0.0586 with a 95% confidence interval of -0.0095-0.0099. The Mod-MPI and isovolumetric relaxation time increased throughout the gestational weeks. The isovolumetric contraction time increased until 24 weeks of gestation and then slightly decreased afterwards, and the ejection time also increased until 31 weeks of gestation and then decreased. There was no significant difference in the Mod-MPI between right CDH and normal fetuses. The automated system showed high inter- and intra-operator reproducibility. Furthermore, the normal reference values of Mod-MPI for each gestational age were established. Our results suggest that the automated system might be clinically feasible for evaluating fetal cardiac function.

Poor Correlation between Fetal Tissue Doppler Imaging and Pulsed Wave Myocardial Performance Indices

INTRODUCTION

Both tissue Doppler imaging (TDI) and pulsed wave Doppler (PWD) Myocardial Performance Indices (MPIs) have been proposed as tools for functional fetal cardiology. We wished to determine if there was any correlation between TDI-MPI and PWD-MPI.

METHODS

A cohort of uncomplicated women with morphologically normal singleton fetuses between 22 and 39 weeks of gestation was recruited. A single sonologist acquired Doppler waveforms for evaluation of both left and right TDI-MPI and PWD-MPI. The PWD-MPI values were calculated using a previously published algorithm and the TDI-MPI time intervals were measured manually by a single operator.

RESULTS

Achievability and repeatability were high for both modalities. TDI produced significantly lower right MPI values yet significantly higher left MPI values, potentially reflecting their evaluation of physiologically different events, blood flow versus myocardial contraction.

CONCLUSION

This study demonstrates that MPIs measured from PWD and TDI have a weak correlation and cannot be used interchangeably, even with the exclusion of suboptimal TDI-MPI scans from the analysis. Given the lack of correlation between the two methods, the high variation in TDI waveform, and the lack of unified approach to TDI analysis, we feel further research is needed before adoption of this technique.

Fetal Cardiac Function: Myocardial Performance Index

The Myocardial Performance Index (MPI) or Tei index, presented by Tei in 1995, is the ratio of the sum of the duration of the isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT) to the duration of the ejection time (ET). The Modified Myocardial Performance Index (Mod-MPI), proposed in 2005, is considered a reliable and useful tool in the study of fetal heart function in several conditions, such as growth restriction, twin-twin transfusion syndrome, maternal diabetes, preeclampsia, intrahepatic cholestasis of pregnancy, and adverse perinatal outcomes. Nevertheless, clinical translation is currently limited by poorly standardised methodology as variations in the technique, machine settings, caliper placement, and specific training required can result in significantly different MPI values. This review aims to provide a survey of the relevant literature on MPI, present a strict methodology and technical considerations, and propose future research.

Reference values for fetal Doppler-based cardiocirculatory indices in monochorionic-diamniotic twin pregnancy

Background

Placental anastomoses in monochorionic diamniotic (MCDA) twin pregnancy have a major impact on fetal circulation. This study was designed to define reference ranges of cardiac and vascular Doppler indices in MCDA twin pregnancies.

Methods

This cross-sectional study included 442 uncomplicated MCDA twin fetuses undergoing Doppler ultrasonography at 18–35 weeks of gestation. Left and right myocardial performance index (LV-MPI, RV-MPI), E/A ratio of atrioventricular valves, pulsatility indices of umbilical artery, middle cerebral artery (MCA), and ductus venosus (DV), cerebroplacental ratio, peak systolic velocity of MCA, S/a ratio of DV, and early diastolic filling time of ductus venosus (DV-E) were evaluated under standardized settings. The equation models between Doppler indices and gestational age (GA) were fitted. After adjustment for GA, the correlations between MPI and fetal heart rate (FHR), and between MPI and DV indices were analyzed.

Results

Estimated centiles of Doppler indices were derived as a function of GA, being distinct in values from those of singletons. There was no correlation between GA-adjusted MPI and FHR. DV-E was inversely related to LV-MPI.

Conclusions

MCDA twins showed significant changes in some Doppler indices throughout gestation with quantitative differences from singletons, emphasizing the importance of MC twin-specific reference values for clinical application. Further adjustment of MPI for FHR was unnecessary. DV-E is a vascular index indirectly representing fetal diastolic function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-04255-w.

Short-Term Effects of Dexamethasone versus Betamethasone on Ultrasonic Measures of Fetal Well-Being: Cohort from a Blinded, Randomized Trial

INTRODUCTION

Maternal corticosteroid administration for anticipated preterm birth is common; however, the corticosteroid effect on fetal ultrasound and cardiotocograph (CTG) remains contested. This study aimed to evaluate short-term ultrasound and CTG impact of (a) dexamethasone versus betamethasone (b) pooled corticosteroid effect.

METHODS

Substudy of blinded randomized trial of dexamethasone versus betamethasone (given <34 weeks). Umbilical artery (UA), middle cerebral artery (MCA), ductus venosus (DV), and uterine artery Doppler, myocardial performance index (MPI), biophysical profile (BPP), and CTG measured pre-corticosteroid then 1, 2, 4, and 7 days post-corticosteroid.

RESULTS

Of 47 fetuses (39 singleton; 4 dichorionic, diamniotic twins; and 4 monochorionic, diamniotic twins) in the February 2012-2013 period, 24 received dexamethasone and 23 betamethasone at average gestation 29.8 ± 2.9 weeks. Thirteen pregnancies (30%) had pre-corticosteroid fetal concerns (estimated weight <10th centile and/or abnormal UA/MCA Doppler). Few significant differences were seen post-corticosteroid: DV pulsatility index and right MPI initially decreased 15-20%, and average BPP decreased slightly on days 1-2. There were no major differential effects of dexamethasone versus betamethasone.

DISCUSSION/CONCLUSION

No substantive post-corticosteroid effects were seen for most ultrasound/CTG measures in fetuses with heightened preterm birth risk but predominantly normal pre-corticosteroid measures. Clinically, this suggests avoiding overreliance on individual measures for delivery decisions post-corticosteroid; equally, multiple/marked ultrasound changes suggest true pathology and not corticosteroid effect.

Reference ranges of fetal heart function using a Modified Myocardial Performance Index: a prospective multicentre, cross-sectional study

OBJECTIVES

The primary aim of this study was to establish the normal reference ranges of the fetal left ventricular (LV) Modified Myocardial Performance Index (Mod-MPI). A secondary aim was to evaluate the agreement between manual and automatic measurements for fetal Mod-MPI.

DESIGN

A prospective, multicentre, cross-sectional study.

PARTICIPANTS

Normal singleton pregnancies.

METHODS

The LV functions of normal singleton pregnancies were assessed in nine centres covering eight provinces in China using unified ultrasound protocols and settings and standardised measurements by pulsed Doppler at 20-24, 28-32 and 34-38 weeks of gestation. The isovolumetric relaxation time (IRT), isovolumetric contraction time, ejection time (ET) and Mod-MPI were measured both automatically and manually.

RESULTS

This cross-sectional study included 2081 fetuses, and there was a linear correlation between gestational age (GA) and Mod-MPI (0.416+0.001×GA (weeks), p<0.001, r²=0.013), IRT (36.201+0.162× GA (weeks), p<0.001, r²=0.021) and ET (171.418-0.078*GA (weeks), p<0.001, r²=0.002). This finding was verified using longitudinal data in a subgroup of 610 women. The agreement between the manual and automated measurements for Mod-MPI was good.

CONCLUSIONS

We constructed normal reference values of fetal LV Mod-MPI. Automatic measurement can be considered for ease of measurement in view of the good agreement between the automatic and manual values.

Spectral Doppler, tissue Doppler, and speckle-tracking echocardiography for the evaluation of fetal cardiac function: an update

The functional assessment of the fetal heart has been incorporated into cardiac ultrasound screening as a routine procedure, encompassing fetuses with and without structural heart diseases. It has long been known that various cardiac and extracardiac conditions, such as fetal growth restriction, fetal tumors, twin-to-twin transfusion syndrome, fetal anemia, diaphragmatic hernia, arteriovenous fistula with high cardiac output, and congenital heart diseases (valvular regurgitation and primary myocardial disease), can alter hemodynamic status and fetal cardiac function. Several ultrasound and Doppler echocardiographic parameters of fetal cardiovascular disease have been shown to correlate with perinatal mortality. However, it is still difficult to identify the signs of fetal heart failure and to determine their relationship with prognosis. The aim of this study was to review the main two-dimensional Doppler ultrasound parameters that can be used in the evaluation of fetal cardiac function, with a focus on how to perform that evaluation and on its clinical applicability.

Evaluation of the Fetal Left Ventricular Myocardial Performance Index (MPI) by Using an Automated Measurement of Doppler Signals in Normal Pregnancies

The myocardial performance index is widely used as an indicator of the heart’s performance. However, due to the subjective nature of ultrasonic testing, there are differences in the measurements among inspectors, requiring a quantitative and objective assessment. In this study, an automated program was developed to quantitatively evaluate the myocardial performance index (MPI) and the cardiac time intervals in the left ventricle for each trimester. One hundred and thirty-three pregnant women who visited the hospital for prenatal examinations were studied, and skilled inspectors obtained left ventricular blood flow waveforms from 47 fetuses in the 12 weeks, 54 fetuses in the 22 weeks, and 32 fetuses in the 31 weeks of pregnancy using a pulse Doppler mode of ultrasound equipment. The acquired images automatically measured the isovolumetric contraction time (IVCT), isovolumetric relaxation time (IVRT,) ejection time (ET), and filling time (FT), and calculated the Tei index (TI) and the K-index (KI); each interval was manually measured during the actual inspection for comparison. In this study, the ultrasonic Doppler waveform was objectively analyzed and measured by the automated program, and it will help with the evaluation of fetal heart function.

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.

Impact of type I and type II maternal diabetes mellitus on fetal cardiac function assessment parameters using spectral and tissue Doppler

The aim of this study was to evaluate the impact of pregestational diabetes mellitus (DM) on fetal cardiac function two-dimensional parameters using spectral and tissue Doppler. Pregnant women between 20 and 36 + 6 weeks gestation were divided into three groups: controls, type I DM, and type II DM. The right ventricle (RV) and left ventricle (LV) annular velocity peaks were measured using spectral (E, A) and tissue (E', A', S') Doppler. The myocardial performance index was calculated as (isovolumetric contraction time [ICT] + isovolumetric relaxation time [IRT])/ejection time using tissue (MPI') and the spectral Doppler (MPI). A general linear model, with fetal heart rate as a covariant, was used to evaluate the effect of DM on the fetal heart function assessment parameters. To assess the association of type I and II DM with adverse perinatal outcomes, Fisher's exact test was used. A receiver operating characteristic curve was used to determine the best cutoff for fetal cardiac function assessment parameters to identify the neonatal composite outcomes. The sample comprised 179 pregnant women. DM had significant effect on RV and LV A peak velocities (p = 0.026 and p = 0.011, respectively). LV ICT (p < 0.001) and LV MPI (p < 0.001) were significantly affected by maternal DM. Fetuses from pregnant women with type II DM showed significantly higher LV MPI (0.492 vs. 0.459, p = 0.006) and RV S' (7.2 vs. 6.44 cm/s, p = 0.024) than controls. Fetuses from type I DM pregnant women showed increase in cardiac parameters that evaluated the LV and RV diastolic function (LV IRT' p < 0.001 and RV MPI' p = 0.044). Type I and II DM were associated with adverse perinatal outcomes: neonatal intensive care unit stay (p < 0.0001), macrosomia (p < 0.0001), hyperbilirubinemia (p < 0.0001), and hypoglycemia (p < 0.0001). The LV MPI' showed significant but moderate sensitivity in identifying the composite neonatal outcomes (AUC: 0.709, 95% CI 0.629-0.780, p < 0.001). Tissue Doppler and MPI parameters can be useful to detect subclinical cardiac dysfunction in the fetal heart of pregestational DM pregnant women.

The value of echocardiography and Doppler in the prediction of fetal demise after laser coagulation for TTTS: A systematic review and meta-analysis

This study aimed to investigate the value of echocardiography and Doppler before fetoscopic laser coagulation for twin‐twin transfusion syndrome (TTTS) in the prediction of intrauterine fetal demise (IUFD). We performed a systematic review and meta‐analysis to compare preoperative parameters between fetuses with and without demise after laser surgery. Eighteen studies were included. Recipient twins have an increased risk of demise in case of preoperative absent/reversed flow (A/REDF) in the umbilical artery (odds ratio [OR] 2.76, 95% confidence interval [CI], 1.78‐4.28), absent or reversed a‐wave in the ductus venosus (OR 2.32, 95% CI, 1.70‐3.16), or a middle cerebral artery peak systolic velocity > 1.5 multiples of the median (MoM) (OR 7.59, 95% CI, 2.56‐22.46). In donors, only A/REDF in the umbilical artery (OR 3.40, 95% CI, 2.68‐4.32) and absent or reversed a‐wave in the ductus venosus (OR 1.66, 95% CI, 1.12‐2.47) were associated with IUFD. No association was found between donor‐IUFD and preoperative myocardial performance index (MPI). Two studies found an association between abnormal MPI and recipient demise. With this study, we have identified a set of preoperative Doppler parameters predictive of fetal demise after laser surgery. More research is needed to assess the utility of preoperative echocardiographic parameters such as the MPI in predicting IUFD.

What's already known about this topic?

Doppler parameters are associated with fetal demise after laser surgery.

Echocardiographic parameters are currently not used in risk stratification.

What does this study add?

A more extensive set of preoperative Doppler parameters is defined to predict post‐laser fetal demise.

The utility of preoperative echocardiographic parameters such as the MPI in predicting fetal demise remains unclear.

Reference ranges for the left ventricle modified myocardial performance index, respective time periods, and atrioventricular peak velocities between 20 and 36 + 6 weeks of gestation

Objective: To establish reference ranges for the fetal left ventricle (LV) modified myocardial performance index (Mod-MPI), respective time periods, and right and left atrioventricular peak velocities between 20 and 36 + 6 weeks of gestation.Methods: This cross-sectional study evaluated 360 low-risk singleton pregnancies between 20 and 36 + 6 weeks of gestation. The LV Mod-MPI was calculated as (isovolumetric contraction time + isovolumetric relaxation time)/ejection time. Polynomial regression was used to obtain the best-fit using Mod-MPI and atrioventricular peak velocity measurements and gestational age (GA) with adjustments using the coefficient of determination (R²). The intra- and interobserver reliability was evaluated using the concordance correlation coefficient (CCC).Results: LV Mod-MPI (R² = 0.026, p = .002) and isovolumetric relaxation time (IRT) (R² = 0.036, p < .001) significantly increased with advancing GA. Isovolumetric contraction time (ICT) and ejection time (ET) did not significantly change with GA. RV and LV E wave, A wave, and E/A ratio significantly increased with GA (p < .001). The mean of each parameter ranged as follows: LV Mod-MPI (0.44-0.47 s), IRT (0.041-0.045 s), ICT (0.032-0.034 s), ET (0.167-0.167 s), RV E (30.2-46.91 cm/s), RV A (47.1-60.7 cm/s), RV E/A (0.65-0.78 cm/s), LV E (27.0-41.4 cm/s), LV A (43.2-53.8 cm/s), and LV E/A (0.63-0.78 cm/s). Only LV A wave measurements demonstrated an intraobserver CCC >0.80. The remaining intra- and interobserver reproducibility parameters demonstrated lower CCC.Conclusions: Reference values were replicated for the fetal LV Mod-MPI and LV and RV transvalvular peak velocities between 20 and 36 + 6 weeks of gestation.

Z-Score Reference Ranges for Fetal Heart Functional Measurements in a Large Brazilian Pregnant Women Sample

The objective of this study was to determine the reference values for fetal heart functional measurements at 24 and 34 weeks of gestation and to develop Z-score equations for all measurements. A single-center, prospective, cross-sectional study with normal fetuses between 24 and 34 weeks of gestation was performed. All pregnant women underwent a comprehensive fetal Doppler echocardiogram with anatomical and functional analysis. Measurements of left and right cardiac output, combined cardiac output, mitral and tricuspid valve flow, inferior vena cava flow, and pulmonary vein flow were performed. The Shapiro-Wilk test and histogram evaluation were performed on all variables. Linear regression was used to assess the relationships between measurements and gestational age. A total of 612 pregnant women with singleton and normal fetuses were included. We assessed the reference values and percentiles of cardiac function as a function of gestational age. The variables that were not normally distributed were subjected to logarithmic or square root transformation. Eleven Z-score equations were developed, with equations for left and right ventricle output and combined cardiac output that were dependent on gestational age and with other equations that were independent of gestational age. The present study produced a large database, allowing the demonstration of reference values and percentiles as well as the development of Z-score equations to facilitate the echocardiographic evaluation of fetal heart function.

The effect of increased amnion volume severity on fetal Doppler indices and perinatal outcomes in idiopathic polyhydramnios

Aim: To evaluate the relationship between polyhydramnios severity and alterations in Doppler indices and perinatal outcomes in idiopathic polyhydramnios.Methods: This prospective case control study was conducted in a tertiary hospital with 173 singleton pregnancies between 29 and 41 weeks gestational age between May 2015 and December 2016. Polyhydroamnios is classified as mild (amniotic fluid index 25-30 cm), moderate (30.1-35 cm), and severe (>35 cm) and the number of the patients in mild, moderate, and severe groups were 55, 39, and 26, respectively. The results were compared with 53 healthy controls. Fetal echocardiography and Doppler measurements of the groups were made and the perinatal outcomes from each group were noted. The relationship between the results and the severity of polyhydramnios was analyzed statistically.Results: The myocardial performance index was significantly higher in the fetuses of women with severe polyhydramnios compared to the other groups (p = .006). There were statistically significant differences among the groups in terms of first and fifth minutes according to the Apgar scores (p = .011, p = .016 respectively). In the severe polyhydramnios group compared with other groups, the middle cerebral artery pulstatility index was significantly lower (p = .002), while middle cerebral artery peak systolic velocity and umbilical artery pulstatility index values were significantly higher (p = .0001, p = .045).Conclusions: Our study showed an increase in myocardial performance index and middle cerebral artery peak systolic velocity values and a decrease in middle cerebral artery pulstatility index values, especially in the severe idiopathic polyhydramnios group. Idiopathic polyhydramnios were associated with low first and fifth minute Apgar score. Additionally, the increase in umbilical artery pulstatility index value and the decrease in middle cerebral artery pulstatility index value became more apparent with the increase in amniotic fluid volume. It should be taken into consideration that brain sparing effect may develop especially in cases with severe polyhydramnios.

Measurement of cardiac function by cardiac time intervals, applicability in normal pregnancy and twin-to-twin transfusion syndrome

BACKGROUND

To detect early cardiac deterioration, a simple and stable tool is needed. Measurement of time intervals in a simple 4-chamber view using color-coded tissue Doppler imaging is a relatively new approach to assess fetal cardiac function. The aim of this study was to evaluate the applicability of this modality and to construct reference ranges for cardiac time intervals.

METHODS

We performed a prospective longitudinal cohort study in healthy fetuses. We used linear mixed models to construct age-adjusted reference ranges for shortening time (St) and lengthening time (Lt) in three cardiac regions: global heart and right and left ventricular wall. St and Lt were expressed as percentage of the cardiac cycle. Feasibility and intra- and interobserver variabilities were evaluated. We applied the technique to twin-twin transfusion syndrome (TTTS) recipients before laser therapy to test the diagnostic performance.

RESULTS

A total of 251 recordings were obtained from 54 healthy singletons. St decreased and Lt increased with gestational age in all regions. We found a high feasibility (99.6%) and excellent intra-/interobserver variability for St (0.96/0.94) and Lt (0.99/0.96) of the global heart. Left and right ventricle performance parameters were good. In TTTS recipients, St was prolonged (p < 0.01) and Lt was shortened (p < 0.01) in all regions and the feasibility was excellent (96.6%).

CONCLUSIONS

The assessment of fetal cardiac function by measurement of cardiac time intervals is technically feasible with good reproducibility, even in difficult scanning circumstances such as TTTS. It is possible to discriminate between healthy and compromised fetuses with this technique.

Fetal myocardial performance index in assessment and management of small-for-gestational-age fetus: a cohort and nested case-control study

OBJECTIVE

To assess the clinical utility of the fetal myocardial performance index (MPI) in assessment and management of the small-for-gestational-age (SGA) fetus/growth-restricted fetus (FGR).

METHODS

This was a prospective cohort study in metropolitan Australia of patients referred in the period June 2012 to March 2015 to fetal medicine services at 24-38 weeks' gestation for suspected singleton SGA/FGR (estimated fetal weight (EFW) < 10^th centile with or without abnormal umbilical artery (UA) Doppler) pregnancy. Patients had MPI assessed in addition to routine measures, and were followed through to birth. We compared MPI values against those of a local reference population and gestational age-matched controls, and assessed the correlation with perinatal outcome and other Doppler measures.

RESULTS

Fifty-two cases were included, 38 diagnosed < 32 weeks and 14 diagnosed ≥ 32 weeks. None demonstrated significantly elevated left, right or delta MPI compared with the reference population or with gestational age-matched controls at the time of first MPI evaluation. There were no consistent longitudinal patterns in MPI that would suggest its clinical utility. The mean ± SD gestational age at delivery was 34.6 ± 3.8 weeks and birth weight was 1.7 ± 0.6 kg, and the median neonatal hospital admission time was 27 days, confirming a pathological cohort. There were no significant correlations between left, right or delta-MPI and perinatal outcome, although there were significant correlations between UA, middle cerebral artery (MCA) and ductus venosus (DV) Doppler and perinatal outcome (birth weight, gestational age at birth and length of neonatal hospital stay). Exploratory subgroup comparisons (EFW < 3^rd vs 3^rd -10^th centile; early- vs late-onset; abnormal vs normal UA Doppler) found only minor differences in MPI, reaching statistical, but not clinical, significance, only in the EFW < 3^rd vs 3^rd -10^th centile comparison.

CONCLUSIONS

MPI did not demonstrate clinical utility in either triage or longitudinal follow-up of an SGA/FGR cohort presenting to fetal medicine services. Given that prior research suggesting its utility originates from single-center cohorts, while multicenter, large cohorts have suggested little utility or no additional utility if routine UA/MCA/DV Doppler is performed, publication bias may have affected previous reports. It seems unlikely that MPI has clinical utility in assessment and management of SGA/FGR fetuses. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Prospective longitudinal assessment of the fetal left modified Myocardial Performance Index

INTRODUCTION

The fetal left modified Myocardial Performance Index (Mod-myocardial performance index (MPI)) is a measure of systolic versus diastolic time intervals obtained from a single cardiac cycle with ultrasound. It is a measure of global ventricular function and has been investigated for potential utility in fetal conditions associated with cardiac dysfunction.

OBJECTIVES

The objective of this study is to compare values from a precisely replicated fetal left Mod-MPI technique to published reference ranges.

METHODS

Three hundred and sixty-five nulliparae prospectively underwent fetal left Mod-MPI measurement at 27⁺⁰-29⁺⁰ and 35⁺⁰-37⁺⁰ weeks' gestation. Measurements from pregnancies complicated by gestational diabetes mellitus, preeclampsia, or a small-for-gestational-age (<10th centile) infant were excluded. Mod-MPI values were compared with three published references created using similar measurement techniques.

RESULTS

Compared with one selected reference, at 29⁺⁰ and 35⁺⁰-37⁺⁰ weeks' gestation, 90-100% of our values fell within the 5th-95th percentile range as expected. Thus, this reference range was validated for our population in late pregnancy. However, the expected level of concordance was not seen at 27⁺⁰-28⁺⁶ weeks'. The other two references to which we compared our Mod-MPI values demonstrated poor concordance, especially at 27⁺⁰-29⁺⁰ weeks'. Pearson interobserver correlation was also improved at 35⁺⁰-37⁺⁰ weeks' at 0.434, compared with 0.083 at 27⁺⁰-29⁺⁰ weeks' gestation.

CONCLUSIONS

Concordance and interobserver variability between our cohort and similar populations were both improved at 35⁺⁰-37⁺⁰ weeks' compared with 27⁺⁰-29⁺⁰ weeks' gestation. Overall, variable Mod-MPI reproducibility across gestations limits clinical application, especially earlier in pregnancy. Manual Mod-MPI measurement should be considered most reliable in late pregnancy until automated MPI measurement is possible.

Beat-to-beat variability of fetal myocardial performance index

OBJECTIVES

To determine whether there is beat-to-beat (BTB) variability in the fetal left myocardial performance index (MPI), as evaluated by an automated system, and whether there is a correlation between MPI and fetal heart rate (FHR).

METHODS

This was a prospective cross-sectional study of uncomplicated, morphologically normal, singleton pregnancies at 20-38 weeks' gestation. Multiple cineloops for left MPI measurement were acquired during a single examination of each fetus. Raw cineloop data were analyzed by our automated MPI system (intraclass correlation coefficient of 1.0 for any given waveform) to produce a set of MPIs. The corresponding instantaneous FHR was measured for each individual cardiac cycle for which MPI was calculated.

RESULTS

Data from 29 fetuses were analyzed; mean MPI was 0.52, mean FHR was 150 beats per min and the median number of cardiac cycles examined per fetus was 70 (interquartile range, 31-115). Marked BTB variability was noted; median coefficient of variation was 10% (range, 5.5-13.9%). FHR was weakly correlated with absolute MPI (r = 0.22; P < 0.05). BTB variation in MPI as a percentage of the mean MPI was not significantly correlated with FHR (r = 0.031; P = 0.146). When standard error of the mean of all MPI values was divided by the mean for each case, it showed that at least four cardiac cycles should be averaged to reduce MPI variability to approximately ± 5%.

CONCLUSION

There is significant BTB variability in fetal left MPI, which has an overall weak correlation with FHR. This could be a factor affecting the consistency of MPI values reported by different research groups. Variability would be reduced by averaging 4-5 cardiac cycles per fetus. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Evaluation of an automated fetal myocardial performance index

OBJECTIVE

To compare automated measurements of the fetal left myocardial performance index (MPI) with manual measurements for absolute value, repeatability and waveform acceptability.

METHODS

This was a multicenter international online study using images from uncomplicated, morphologically normal singleton pregnancies (16-38 weeks' gestation). Single Doppler ultrasound cardiac cycle images of 25 cases were selected, triplicated and randomized (n = 75). Six senior observers, unaware of the repetition of images, manually calculated MPI for each waveform and the results were compared with automation. Intraobserver repeatability and interobserver reproducibility were assessed using intraclass correlation coefficients (ICCs) and 95% CI. The agreement between each observer's manual MPI measurements and corresponding automated measurements was evaluated using Bland-Altman plots and ICCs with 95% CI. The degree of variation between experts in the classification of fetal MPI waveform quality was assessed using individual cardiac cycle left MPI images previously classified by two authors as 'optimal', 'suboptimal' or 'unacceptable', with 30 images selected for each quality group. Ten images in each category were duplicated and the resulting 120 images were randomized and then classified online by five observers. The kappa statistic (κ) was used to demonstrate interobserver and intraobserver agreement and agreement of classifications by the five observers.

RESULTS

The automated measurement software returned the same value for any given image, resulting in an ICC of 1.00. Manual measurements had intraobserver repeatability ICC values ranging from 0.69 to 0.97, and the interobserver reproducibility ICC was 0.78. Comparison of automated vs manual MPI absolute measurements for each observer gave ICCs ranging from 0.77 to 0.96. Interobserver image quality classification agreement gave k = 0.69 (P < 0.001), and the intraobserver agreement was variable (κ ranging from 0.40 to 0.81).

CONCLUSIONS

Automated fetal MPI provides superior repeatability and reproducibility to manual methodology. Additionally, experts vary significantly when classifying suitability of fetal MPI waveforms. Automated MPI may facilitate clinical translation by removing human subjectivity. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Fetal colour tissue Doppler imaging (cTDI): biventricular reference ranges for the time segments of the cardiac cycle in second and third trimesters of gestation

PURPOSE

To construct biventricular reference ranges for isovolumic time intervals (isovolumic contraction time, ICT; isovolumic relaxation time, IRT) and ejection time (ET) for colour tissue Doppler imaging (cTDI) between 15 and 37 weeks' in healthy fetuses.

METHODS

This was a prospective multicentre cross-sectional study involving 160 singleton pregnancies between 15 and 37 weeks of gestation, using cTDI. ICT, ET, IRT and myocardial performance index (MPI) were analysed offline using a small region of interest (ROI) within the basal part of the right and left ventricular wall immediately distal to the annulus. Regression analysis was used to determine gestational age-adjusted reference ranges and to construct nomograms for cTDI parameters.

RESULTS

Right and left ventricular ICT (p = 0.004 and p < 0.001) and ET (p = 0.011 and p = 0.050) increased, whereas IRT (p = 0.862 and p = 0.067) and MPI (p = 0.476 and p = 0.777) remained constant with gestational age.

CONCLUSIONS

This is the first study to evaluate fetal isovolumic time intervals in the second and third trimesters of gestation using cTDI. Normal data for fetal isovolumic time intervals and biventricular MPI by colour tissue Doppler imaging are provided. The reference ranges may be useful in research or clinical studies and can be used in fetuses with compromised cardiac function.

Fetal left modified myocardial performance index measured by the Auto Mod-MPI system: development of reference values and application to recipients of twin-to-twin transfusion syndrome

OBJECTIVES

To establish normal reference ranges for the fetal left modified myocardial performance index (Mod-MPI) measured by the Auto Mod-MPI system and evaluate Mod-MPI changes in recipients of twin-to-twin transfusion syndrome (TTTS) before and after fetoscopic laser coagulation.

METHODS

This was a prospective longitudinal study of normal singleton fetuses from 12.0 to 40.0 weeks of gestation. TTTS cases treated by laser coagulation were reviewed for Mod-MPI measurements of recipients. All measurements were performed using the Auto Mod-MPI system by a single experienced operator.

RESULTS

Among a total 447 examinations from 222 fetuses, we were unable to measure the Mod-MPI in two cases, and therefore, 445 examinations were analyzed. The median Mod-MPI consistently increased from 0.44 to 0.56 throughout gestation. The median isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT) also increased with advancing gestational age. The ejection time (ET) increased until 27 weeks of gestation and decreased thereafter. In the 30 recipients, Mod-MPI, ICT, and IRT increased before laser coagulation and significantly decreased after laser coagulation.

CONCLUSION

Normal reference values for left Mod-MPI were established using the Auto Mod-MPI system, and these might be useful for assessing cardiac function in TTTS. © 2016 John Wiley & Sons, Ltd.

Monitoring intrahepatic cholestasis of pregnancy using the fetal myocardial performance index: a cohort study

OBJECTIVE

To investigate use of the fetal myocardial performance index (MPI) in assessing intrahepatic cholestasis of pregnancy (ICP).

METHODS

This was a cohort study including cross-sectional and longitudinal data from 31 women with ICP recruited from June 2012 to March 2014. Fetal left, right and delta MPI (LMPI, RMPI and DMPI), and routine measures of fetal growth and wellbeing, were obtained at each ultrasound examination. Results were evaluated with respect to gestational age (GA)-adjusted reference intervals, level of maternal serum bile acid (SBA) and fetal outcome. Lower SBA (≥ 7.5 and < 40 μmol/L) and high SBA (≥ 40 μmol/L) subgroups of cases were defined for the analysis.

RESULTS

A total of 51 ultrasound examinations were performed in 33 fetuses. The mean LMPI, and means of its isovolumetric relaxation time (IRT) and isovolumetric contraction time (ICT) components were significantly higher in all subgroups of cases of ICP relative to the normal reference mean. Considering only the first examination in each case of ICP, IRT was significantly more prolonged in the high SBA group (n = 10) in comparison to the lower SBA group (n = 23) (52.7 ± 8.0 ms vs 47.3 ± 4.8 ms, P = 0.02), and both IRT (r = 0.538, P = 0.001) and LMPI (r = 0.367, P = 0.036) were significantly correlated with SBA concentration. The proportion of high SBA cases with LMPI, RMPI or DMPI > 2 SD above the GA-adjusted reference mean was not significantly greater than for the lower SBA group. On analysis of all data from those cases with more than one examination, no significant correlation was found between SBA concentration and any of the MPI variables.

CONCLUSIONS

LMPI values increase above the population GA-adjusted mean in cases of ICP, particularly amongst women with higher SBA. A significant correlation between IRT and LMPI at initial examination and increasing SBA concentration was found. A future multicenter prospective study may clarify the prognostic utility of MPI in ICP.

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.

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.

Automated fetal cardiac valve movement detection for modified myocardial performance index calculation

The Modified Myocardial Performance Index (Mod-MPI) is becoming an important index in fetal cardiac function evaluation. However, the current method for Mod-MPI calculation can be time-consuming and demonstrates poor inter-operator repeatability. This paper presents an automated method for detecting the opening and closing events of fetal cardiac valves with the aim of automating the Mod-MPI calculation. Fifty-four Doppler ultrasound images, showing blood inflow and outflow for the left ventricle, are analyzed to attempt to automatically detect the timings of a total of 905 opening and closing events for both aortic and mitral valves. Timings are found according to the morphological characteristics of waveforms as well as intensity information of images. The proposed method can detect the four valve movement events with high sensitivity (95.60-98.64%) and precision (96.85-100.00%). Results are verified by comparison with manual annotation of same images from an expert.

Influence of equipment and settings on myocardial performance index repeatability and definition of settings to achieve optimal reproducibility

OBJECTIVE

To compare left myocardial performance index (MPI) values and reproducibility using different settings and ultrasound equipment in order to standardize optimal machine settings.

METHODS

Left MPI was prospectively evaluated by one observer performing conventional Doppler in 62 fetuses (28-36 weeks of gestational age) using different settings (changing sweep speed, gain and wall motion filter (WMF)) and two different ultrasound devices (Siemens Antares, Siemens; Voluson 730 Expert, GE Medical Systems). Intraclass coefficients of agreement (ICCs) were calculated using Bland-Altman analysis.

RESULTS

Using baseline settings on the Siemens, mean (SD) MPI was 0.44 (0.05) with an ICC of 0.81. Decreasing the sweep speed resulted in decreasing average MPI values (0.43) and decreasing ICC (0.61). Lowering gain also influenced average MPI values (0.46) and ICC (0.76). Raising gain resulted in similar MPI values (0.45) with better ICC (0.90) compared with baseline settings. Raising wall motion filter (WMF) provided the best ICC (0.94) compared with the other settings. Changing the ultrasound equipment resulted in an ICC of 0.64. The optimal settings to achieve the highest reproducibility in measurement of MPI were sweep speed 8, gain 60 dB and WMF 281 Hz for Siemens Antares and sweep speed 5, gain -10 dB and WMF 210 Hz for Voluson 730 Expert.

CONCLUSION

Changing ultrasound settings or equipment may affect the calculation and repeatability of measurement of MPI values. Strict standardization of methods decreases the variability of this parameter for fetal cardiac function assessment.

Feasibility of using auto Mod-MPI system, a novel technique for automated measurement of fetal modified myocardial performance index

OBJECTIVES

To evaluate the reproducibility of measurement of the fetal left modified myocardial performance index (Mod-MPI) determined using a novel automated system.

METHODS

This was a prospective study of 116 ultrasound examinations from 110 normal singleton pregnancies at 12 + 1 to 37 + 1 weeks' gestation. Two experienced operators each measured the left Mod-MPI twice manually and twice automatically using the Auto Mod-MPI system. Intra- and interoperator reproducibility were assessed using intraclass correlation coefficients (ICCs) and the manual and automated measurements obtained by the more experienced operator were compared using Bland-Altman plots and ICCs.

RESULTS

Both operators successfully measured the left Mod-MPI in all cases using the Auto Mod-MPI system. For both operators, intraoperator reproducibility was higher when performing automated measurements (ICC = 0.967 and 0.962 for Operators 1 and 2, respectively) than when performing manual measurements (ICC = 0.857 and 0.856 for Operators 1 and 2, respectively). Interoperator agreement was also better for automated than for manual measurements (ICC = 0.930 vs 0.723, respectively). There was good agreement between the automated and manual values measured by the more experienced operator.

CONCLUSIONS

The Auto Mod-MPI system is a reliable technique for measuring fetal left Mod-MPI and demonstrates excellent reproducibility.

Ultrasound assessment of fetal cardiac function

Introduction: Fetal heart evaluation with US is feasible and reproducible, although challenging due to the smallness of the heart, the high heart rate and limited access to the fetus. However, some cardiac parameters have already shown a strong correlation with outcomes and may soon be incorporated into clinical practice. Materials and Methods: Cardiac function assessment has proven utility in the differential diagnosis of cardiomyopathies or prediction of perinatal mortality in congenital heart disease. In addition, some cardiac parameters with high sensitivity such as MPI or annular peak velocities have shown promising results in monitoring and predicting outcome in intrauterine growth restriction or congenital diaphragmatic hernia. Conclusion: Cardiac function can be adequately evaluated in most fetuses when appropriate expertise, equipment and time are available. Fetal cardiac function assessment is a promising tool that may soon be incorporated into clinical practice to diagnose, monitor or predict outcome in some fetal conditions. Thus, more research is warranted to further define specific protocols for each fetal condition that may affect cardiac function.

The short term fetal cardiovascular effects of corticosteroids used in obstetrics

Background: Corticosteroids are widely used in obstetrics due to their striking effect on perinatal morbidity and mortality of premature neonates. Despite this, relatively few studies have explored short term fetal effects of corticosteroids as measured by ultrasound. Objectives: 1) To present a literature review of short term fetal cardiovascular effects of corticosteroids 2) To describe the protocol of a current observational study (SUPER-A*STEROID) of cardiovascular effects of dexamethasone and betamethasone in the first week after their administration. This trial is nested within the A*STEROID blinded multicentre randomised controlled trial of the two steroid preparations. Findings: Existing data suggest corticosteroids have little effect on the major measured fetal blood vessels when the baseline ultrasound is normal. In the compromised fetus, where the umbilical artery end-diastolic flow is abnormal prior to maternal corticosteroids, flow is temporarily restored in approximately 50% of cases. Whether such changes are beneficial is uncertain. Very little data exist that directly compare the short-term effects of betamethasone and dexamethasone. The SUPER- A*STEROID study described will help provide this information.