Measuring left ventricular myocardial performance index in fetuses

Transitional Hemodynamics in Neonates Born Through Meconium-Stained Amniotic Fluid: A Prospective Observational Study

Neonates born through meconium-stained amniotic fluid (MSAF) are at increased risk of altered cardiopulmonary transition at birth. There is a paucity of literature evaluating the transitional hemodynamics in these neonates. We aimed to evaluate transitional hemodynamics via echocardiography in neonates born through MSAF, compared to healthy neonates. The primary objective was to assess pulmonary vascular resistance using left pulmonary artery-velocity time integral (LPA-VTI). The secondary objectives were to assess other pulmonary vascular parameters and myocardial function. We enrolled 35 MSAF-born and 35 healthy neonates. Echocardiography was performed at 24 and 48 h of life by a pediatric cardiologist. Echocardiographic parameters were compared between MSAF-born and healthy neonates, and between MSAF-born neonates who developed meconium aspiration syndrome (MAS) and who did not (non-MAS). Among 35 MSAF-born neonates, 14 (40%) were non-vigorous, 18 (51%) required admission to neonatal intensive care unit, 8 (23%) developed MAS, 3 (9%) pulmonary hypertension and 1 (3%) air leak. On echocardiography, LPA-VTI (cm; mean ± SD) was significantly decreased at 24 and 48 h in MSAF-born neonates (14.38 ± 2.48; 15.55 ± 2.48), compared to healthy neonates (16.60 ± 2.14; 17.66 ± 2.71), respectively. Further, LPA-VTI was significantly reduced at 24 and 48 h among MAS (11.81 ± 3.0; 12.43 ± 2.5), compared to non-MAS neonates (15.15 ± 1.72; 16.48 ± 1.55), respectively. Other pulmonary vascular and myocardial function parameters were comparable between the two groups. Pulmonary adaptation was significantly delayed in neonates with MSAF, which was more pronounced in MAS neonates. Further studies should explore the utility of these parameters for early prediction of cardiorespiratory morbidities in this population.

Assessment of fetal cardiac function in early fetal life: feasibility, reproducibility, and early fetal nomograms

BACKGROUND

Fetal cardiology has shown a rapid development in the past decades. Fetal echocardiography is not only used for the detection of structural anomalies but also to assess fetal cardiac function. Assessment of the fetal cardiac function is performed mostly in the second and third trimesters. The study of fetal cardiac function at the end of first trimester has not been investigated properly, and there is a lack of reference values at early gestational weeks.

OBJECTIVE

This study aimed to assess if the measurement of time-related parameters of cardiac function in the left ventricle of the fetal heart is feasible and reproducible at the end of the first trimester. If possible, we provide nomograms of these parameters from 11 to 13+6 gestational weeks.

STUDY DESIGN

We conducted a prospective observational study from March to September 2022. The study was carried out in 2 hospitals (Hospital Universitari Dexeus, Barcelona, and Hospital VITAHS 9 Octubre, Valencia, Spain). The scans were performed by 3 specialists in fetal medicine. The exclusion criteria were fetal cardiac rhythm abnormalities, abnormal nuchal translucency, abnormal ductus venosus, fetal malformations, stillbirth, estimated fetal weight <10 percentile, diabetes, and gestational hypertensive disorders. The cardiac function parameters studied in the left ventricle were isovolumetric contraction time, isovolumetric relaxation time, ejection time, filling time, cycle time, myocardial performance index, ejection time fraction, and filling time fraction. We study the feasibility and intra- and interobserver reproducibility of these parameters using the interclass correlation coefficient. Nomograms were created and the percentiles of the values of the different parameters were calculated.

RESULTS

A total of 409 cases were recruited but only 296 could be included in the statistical analysis once the exclusion criteria were applied. The intraobserver reproducibility study was excellent (interclass correlation coefficient >0.900), and the interobserver reproducibility study was good (interclass correlation coefficient >0.700). The data regression analysis showed that cycle time, filling time, isovolumetric contraction time, and filling time fraction increased with gestational age, whereas ejection time fraction decreased with gestational age and myocardial performance index (mean, 0.43±0.08), isovolumetric relaxation time (mean, 0.04±0.01), and ejection time (mean, 0.16±0.01) remained constant from 11 to 13 weeks.

CONCLUSION

The study of fetal cardiac function is feasible and reproducible at 11 to 13+6 gestational weeks. Nomograms of the studied parameters are provided.

How Automated Techniques Ease Functional Assessment of the Fetal Heart: Applicability of MPI+™ for Direct Quantification of the Modified Myocardial Performance Index

(1) Objectives: In utero functional cardiac assessments using echocardiography have become increasingly important. The myocardial performance index (MPI, Tei index) is currently used to evaluate fetal cardiac anatomy, hemodynamics and function. An ultrasound examination is highly examiner-dependent, and training is of enormous significance in terms of proper application and subsequent interpretation. Future experts will progressively be guided by applications of artificial intelligence, on whose algorithms prenatal diagnostics will rely on increasingly. The objective of this study was to demonstrate the feasibility of whether less experienced operators might benefit from an automated tool of MPI quantification in the clinical routine. (2) Methods: In this study, a total of 85 unselected, normal, singleton, second- and third-trimester fetuses with normofrequent heart rates were examined by a targeted ultrasound. The modified right ventricular MPI (RV-Mod-MPI) was measured, both by a beginner and an expert. A calculation was performed semiautomatically using a Samsung Hera W10 ultrasound system (MPI+™, Samsung Healthcare, Gangwon-do, South Korea) by taking separate recordings of the right ventricle's in- and outflow using a conventional pulsed-wave Doppler. The measured RV-Mod-MPI values were assigned to gestational age. The data were compared between the beginner and the expert using a Bland-Altman plot to test the agreement between both operators, and the intraclass correlation was calculated. (3) Results: The mean maternal age was 32 years (19 to 42 years), and the mean maternal pre-pregnancy body mass index was 24.85 kg/m² (ranging from 17.11 to 44.08 kg/m²). The mean gestational age was 24.44 weeks (ranging from 19.29 to 36.43 weeks). The averaged RV-Mod-MPI value of the beginner was 0.513 ± 0.09, and that of the expert was 0.501 ± 0.08. Between the beginner and the expert, the measured RV-Mod-MPI values indicated a similar distribution. The statistical analysis showed a Bland-Altman bias of 0.01136 (95% limits of agreement from -0.1674 to 0.1902). The intraclass correlation coefficient was 0.624 (95% confidence interval from 0.423 to 0.755). (4) Conclusions: For experts as well as for beginners, the RV-Mod-MPI is an excellent diagnostic tool for the assessment of fetal cardiac function. It is a time-saving procedure, offers an intuitive user interface and is easy to learn. There is no additional effort required to measure the RV-Mod-MPI. In times of reduced resources, such assisted systems of fast value acquisition represent clear added value. The establishment of the automated measurement of the RV-Mod-MPI in clinical routine should be the next level in cardiac function assessment.

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.

The effect of nuchal umbilical cord on fetal cardiac and cerebral circulation-cross-sectional study

OBJECTIVES

The subject of our analysis is the influence of umbilical cord collision around the fetal neck on the fetal heart function and cerebral circulation.

METHODS

Our study was carried out on a group of 115 fetuses from single pregnancies with physiological course, during the 15th to 40th week of pregnancy. In our analysis, we examined the following parameters: Tei index for right ventricle, Tei index for left ventricle with Tei index components: isovolumetric contraction time, isovolumetric relaxation time, ejection time and cardiothoracic area ratio, middle cerebral artery peak systolic velocity (PS MCA), middle cerebral artery pulsatility index (PI MCA). Gestational age in our study was: 28+2±34. The study group of patients with fetal umbilical cord around neck group (fUCAN) included 38 fetuses (20 males, 18 females). The control group of patients with no fetal umbilical cord around neck group (NfUCAN) included 77 fetuses (43 males, 34 females).

RESULTS

In our study, we found no significant differences in the values obtained: Tei LV in fUCAN: 0.5±0.1 vs. in NfUCAN: 0.5±0.1; p=0.42), Tei RV in fUCAN: 0.5±0.2 vs. in NfUCAN: 0.4±0.1; (p=0.2). Tricuspid valve regurgitation-TR was observed with the following frequency: fUCAN: 7/38, 18% vs. NfUCAN: 13/77, 17%; p=0.8. MCA PS in study fUCAN group was significantly higher than in NfUCAN (40.2±11.5 vs. 32.5±9.5; p=0.003), although other hemodynamic and clinical variables did not differ between the study and control groups.

CONCLUSIONS

The fetal nuchal umbilical cord collision did not affect the fetal heart function expressed as Tei index, at the time of fetal heart examination (at mean gestational age 29+4 weeks). The fUCAN group presented elevated PS MCA, which was not related to other hemodynamic and clinical variables between the study and control groups.

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.

Inter-twin differences in fetal echocardiographic findings are associated with decreased dual twin survival in twin-twin transfusion syndrome

OBJECTIVE

To determine if inter-twin differences in fetal echocardiographic findings are associated with fetal survival in monochorionic pregnancies complicated by twin-to-twin transfusion syndrome (TTTS).

METHODS

This study included women who underwent laser surgery for TTTS between 2012 and 2018 at a single institution. Echocardiographic cardiac parameters in the donor and recipient twins were compared using Z-scores and regression analyses (adjusted for confounding variables) to determine whether any measurable inter-twin differences were associated with neonatal survival at birth. Results are expressed as (Odds ratio [95% confidence interval], p-value).

RESULTS

Fetal echocardiography and delivery information was available in 124 TTTS cases. Dual live-birth occurred in 72% and at least one live-birth was seen in 89% of cases. Sixty-four percent (51/79) of recipient twins had evidence of cardiac dysfunction compared to 10% (8/79) of the donor twins (p < .01). In the logistic regression, inter-twin differences in left ventricle short axis dimension (0.62[0.44-0.87], p < .01), aortic valve diameter (0.67[0.45-0.99], p = .047), peak systolic velocity across the pulmonary artery (PA-PSV) (0.09[0.01-0.53], p < .01) and mitral valve diameter (0.56[0.38-0.84], p < .01) were associated with lower dual twin survival at birth.

CONCLUSION

Inter-twin differences in left cardiac geometry and function are associated with decreased survival at delivery in TTTS.

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.

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.

Factors associated to early intrauterine fetal demise after laser for TTTS by preoperative fetal heart and Doppler ultrasound

OBJECTIVE

To determine the prognostic value of fetal Doppler and echocardiographic parameters for intrauterine fetal demise (IUFD) within 24 hours and within 1 week after laser coagulation in monochorionic pregnancies complicated by twin-twin transfusion syndrome.

METHOD

This retrospective study correlated the preoperative hemodynamic and echocardiography parameters to the outcome in fetuses with twin-twin transfusion syndrome undergoing laser therapy.

RESULTS

One hundred and twelve laser coagulations were performed between February 2006 and June 2015. The total (single and double) IUFD rate was 27.7%. Further, 59% of IUFD occurred within 24 hours and 74.4% occurred within 1 week after laser. The following were associated to IUFD within 24 hours: the middle cerebral arterial pulsatility index in the donor, abnormal umbilical artery (UA) end diastolic flow, increased middle cerebral artery peak systolic velocity, and right ventricular myocardial performance index (RV-MPI) z-score in the recipient. For IUFD within 1 week were the pulsatility index in the donor UA and the recipient abnormalities in UA, ductus venosus, middle cerebral artery-peak systolic velocity, and RV-MPI z-score.

CONCLUSION

Following laser was early IUFD that was associated with Doppler findings suggesting donor cerebroplacental redistribution, and recipient overload cardiomyopathy, such as abnormal ductus venosus and UA Dopplers as well as an increase of RV-MPI.

Assessment of fetal myocardial performance in severe early onset pre-eclampsia (EO-PET) with and without intrauterine growth restriction across deteriorating stages of placental vascular resistance and links to adverse outcomes

OBJECTIVE

To determine whether fetuses in severe early onset pre-eclampsia (EO-PET) with or without intrauterine growth restriction has cardiac dysfunction across deteriorating stages of placental vascular resistance and whether this dysfunction influences perinatal outcome.

STUDY DESIGN

This was a prospective cross-sectional study performed in a tertiary care university medical centre. Sixty pregnant patients with severe early-onset pre-eclampsia between 27 and 32 weeks were recruited and matched with 60 patients having normal pregnancies. An analysis of cardiac function using the myocardial performance index (MPI) and early ventricular filling (E) and late active atrial contraction (A) ratios (E/A ratios) in the study group was performed compared to controls and further analysis was performed based on worsening placental vascular resistance and presence of growth restriction.

RESULTS

MPI values were increased in the pre-eclamptic group, irrespective if growth restriction co-exists, compared to controls (0.61 vs 0.38, p<0.001). Its median value progressively increased with worsening placental vascular resistance. For adverse perinatal outcome cut-off MPI values have been suggested. The E/A ratios were significantly decreased in the pre-eclamptic group compared to controls (0.66 vs 0.79, p<0.0001). No adverse outcomes were noted in the control group.

CONCLUSION

Fetal cardiac function is significantly impaired in pregnancies complicated by severe early onset pre-eclampsia, irrespective if growth restriction co-exists and worsens with deteriorating grades of placental vascular resistance. The MPI can potentially be integrated into routine fetal surveillance techniques.

Intermediate Diastolic Velocity as a Parameter of Cardiac Dysfunction in Growth-Restricted Fetuses

OBJECTIVE

To evaluate the intermediate intracardiac diastolic velocities in fetuses with growth restriction.

METHODS

Doppler waveforms of the two atrioventricular valves were obtained. Peak velocities of the E (early) and A (atrial) components, and the lowest intermediate velocity (IDV) between them, were measured in 400 normally grown and in 100 growth-restricted fetuses. The prevalence of abnormal IDV, E/IDV, and A/IDV ratios in fetuses presenting with perinatal death or acidemia at birth (pH ≤7.1) was estimated.

RESULTS

IDV was significantly lower and E/IDV ratios significantly higher in the two ventricles of growth-restricted fetuses with reduced diastolic velocities in the umbilical artery (p < 0.05). In 13 fetuses presenting with perinatal death or acidemia at birth, 11 (85%) had either an E/IDV or A/IDV ratio >95th percentile, whereas 5 (38%) showed absent or reversed atrial velocities in the ductus venosus (DV-ARAV; p < 0.04). Fetuses without DV-ARAV but with elevated E/IDV ratios in either ventricle were nearly 7-fold more likely to have perinatal demise or acidemia at birth (OR 6.9, 95% CI 1.4-34) than those with E/IDV ratios <95th percentile.

CONCLUSION

The E/IDV and A/IDV ratios in the two cardiac ventricles might provide information about the risk of perinatal demise or acidemia in growth-restricted fetuses.

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.

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.

Determination of the myocardial performance index in deteriorating grades of intrauterine growth restriction and its link to adverse outcomes

AIM

The aim of this study is to determine the fetal modified myocardial performance index (Mod-MPI) and E-wave/A-wave peak velocities (E/A ratio) in deteriorating grades of intrauterine growth restriction (IUGR) and its link to adverse outcomes defined as perinatal death, hypoxic ischemic encephalopathy, neonatal resuscitation, neonatal cord pH <7.15, intraventricular hemorrhage and bronchopulmonary dysplasia.

METHOD

Forty three pregnant women with IUGR defined as the abdominal circumference <10th percentile for gestational age and umbilical resistance index >2 standard deviations in the third trimester of pregnancy were matched for gestational age and maternal age with 43 women with appropriate-for-gestational-age fetuses. The IUGR group was subdivided on the basis of multivessel Doppler anomalies into different grades of growth restriction. Mod-MPI and E/A ratio were determined and linked to perinatal outcome.

RESULTS

The median Mod-MPI was significantly higher in growth-restricted fetuses compared with controls (0.59 vs 0.37, p < 0.001) and increased with severity of IUGR, the classification of which was based on degree of abnormality of the umbilical resistance index, presence of arterial redistribution and degree of abnormality of the ductus venosus (DV) Doppler indices. A cut-off Mod-MPI value of 0.54 conferred a sensitivity of 87% [confidence interval (CI): 66-97%], specificity of 75% (CI: 55-91%) and a likelihood ratio (LR) of 3.47 for an adverse outcome. A cut-off Mod-MPI value of 0.67 conferred a sensitivity of 100% (CI: 54-100%), specificity of 81% (CI: 65-92%) and LR of 5.28 for perinatal death. No abnormal outcomes occurred in controls. In logistic regression analysis, the MPI remained a significant predictor of adverse outcome after adjusting for gestational age of delivery, fetal weight, E/A ratio, maternal age, DV Doppler indices, amniotic fluid index and umbilical artery resistance index [adjusted odds ratio, 95% CI: 2.60 (1.15-5.83), p-value 0.02]. MPI fared significantly better than the E/A ratio as a predictor of adverse outcome (area under the receiver operating characteristic curve of 0.94 and 0.76, p < 0.001).

CONCLUSION

Fetal myocardial performance deteriorates with severity of growth restriction. There is an association between severity of the MPI elevation and rates of adverse perinatal outcome. The Mod-MPI and E/A ratio have the potential to be integrated into routine surveillance techniques of the growth-restricted fetus. © 2014 John Wiley & Sons, Ltd.

Predictive value of cardiovascular parameters in twin-to-twin transfusion syndrome

OBJECTIVE

To evaluate the prognostic value of the Children's Hospital Of Philadelphia (CHOP) cardiovascular score and the modified myocardial performance index (MPI), in determining the risk of recipient fetal loss in twin-to-twin transfusion syndrome (TTTS).

METHODS

This cohort study was based on data collected prospectively from 105 pregnancies complicated by TTTS (Quintero stages I-IV) and treated with laser photocoagulation between May 2008 and February 2013. Fetuses underwent detailed anatomical and Doppler ultrasonography with cardiac assessment as part of routine care. CHOP score and right MPI were calculated and cut-offs selected using receiver-operating characteristics curve analysis. These were compared according to loss of recipient fetus, using univariate and multivariate logistic regression. The correlation between CHOP score, MPI and Quintero stage was determined and we investigated differences in MPI before and after laser coagulation in a cohort of 90 recipient fetuses.

RESULTS

Rates of recipient fetal loss were significantly higher when the CHOP score was ≥ 3 (39.5% vs 12.9%, P = 0.002) and when MPI z-score was > 1.645 (34.5% vs 10.6%, P = 0.004). After adjustment for Quintero stage, the risk of recipient fetal loss remained significantly higher when the CHOP score was ≥ 3 (odds ratio, 3.09; 95% CI, 1.035-9.21). There was a positive correlation between CHOP score, MPI and Quintero stage. MPI was significantly lower after compared with before laser coagulation.

CONCLUSION

CHOP score and MPI are predictors of recipient fetal loss in TTTS and may be used to supplement Quintero's classification.

Fetal left and right ventricle myocardial performance index: defining normal values for the second and third trimesters--single tertiary center experience

Myocardial performance index (MPI), or Tei index, has become a commonly used parameter for the noninvasive, Doppler-derived assessment of global systolic and diastolic performance of the heart in both adults and children. Normal values have been established in adults and children; however, limited data exist in fetal hearts. The aim of this study was to further elucidate normal values of fetal left (LV) and right ventricle (RV) MPI values in second- and third-trimester fetuses and compare these values with other previously published data. This was a retrospective study to measure MPI in healthy fetuses. After Institutional Review Board approval, 2000 fetal echocardiography studies (FES) were acquired during a period of 4 years. Demographic parameters examined included gestational age (GA), maternal age (MA), and indication for fetal echocardiography. Fetuses with congenital heart disease, arrhythmias, or significant noncardiac fetal anomalies were excluded. The following echocardiography parameters were collected: LV ejection time (LVET), mitral valve close-to-open time (MVCO), RVET, tricuspid valve CO (TVCO), and fetal heart rate. For simplicity, LV and RV MPI values were calculated as follows: LV MPI = MVCO - LVET/LVET and RV MPI = TVCO - RVET/RVET. Four hundred twenty FES met the study criteria. LV MPI was evaluated in 230 and 190 FES in the second and third trimester, respectively. Of the 420 FES, 250 (150 in the second trimester and 100 in the third trimester) had all of the measurements required for RV MPI calculation. MA ranged between 16 and 49 years. Indications for FES included diabetes mellitus (N = 140; 33 %), suspected fetal anomalies on routine obstetrical ultrasound (N = 80; 20 %), autoimmune disorder (N = 60; 14 %), family history of CHD (N = 76; 18 %), medication exposure (N = 22; 5 %), increase nuchal thickness (N = 13; 3 %), and other indications (N = 29; 6 %). Averaged LV and RV MPI values were 0.464 ± 0.08 and 0.466 ± 0.09, respectively. Further analysis based on gestational period showed slightly greater LV and RV MPI values during the third compared with the second trimester, i.e., 0.48 and 0.49, respectively, with no statistically significant difference. There was no significant association of LV and RV MPI with heart rate. To our knowledge, this is the first study to establish normal values of fetal MPI based on a large fetal population from a single tertiary center. LV and RV MPI values were independent of GA and fetal heart rate. MPI is a useful parameter for the assessment of global cardiac function in the fetus and demonstrates good reproducibility with narrow interobserver and intraobserver variability. Its usefulness should be studied in fetal hearts with complex congenital anomalies.

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.

Evaluation of tissue Doppler-derived myocardial performance index in fetuses with intracardiac echogenic focus

OBJECTIVE

To compare cardiac function between fetuses with and without intracardiac echogenic foci (IEFs) by conventional echocardiography and tissue Doppler (TD) imaging.

METHODS

Fetuses having IEF and no additional cardiac or extracardiac anomaly between 20 and 28 weeks (median 22 weeks) of gestation (n = 61) were compared with healthy fetuses between 18 and 29 weeks (median 23 weeks) of gestation (n = 55). Pulmonary artery and aortic peak velocities, atrioventricular (AV) early diastole (E) and atrial contraction (A) velocities and E/A ratios were measured. TD-derived myocardial performance index (MPI) was also measured.

RESULTS

Tricuspid valve E/A ratios, which were 0.634 ± 0.07 versus 0.639 ± 0.06 (p = 0.697), mitral valve E/A ratios, which were 0.604 ± 0.08 versus 0.612 ± 0.07 (p = 0.600), aorta peak velocities, which were 0.709 ± 0.11 versus 0.697 ± 0.11 (p = 0.592) and pulmonary artery peak velocities, which were 0.699 ± 0.12 versus 0.694 ± 0.11 (p = 0.800) in the study and the control groups, respectively. TD-derived measurements in the study and control groups included tricuspid valve MPI, which were 0.452 ± 0.08 versus 0.473 ± 0.09 (p = 0.221) and mitral valve MPI values, which were 0.444 ± 0.1 versus 0.445 ± 0.09 (p = 0.965), respectively, and this difference was not statistically significant.

CONCLUSION

An isolated IEF is not associated with abnormal cardiac function. We suggest that the presence of an isolated IEF should not be an indication for fetal cardiac function examination either with conventional Doppler or TD imaging techniques, unless there is a coexisting cardiac or extracardiac anomaly.

Evaluation of conventional Doppler fetal cardiac function parameters: E/A ratios, outflow tracts, and myocardial performance index

Structural evaluation of the fetal heart is well established. Functional evaluation using pulsed-wave Doppler may also be performed. E/A ratios express the relationship between the maximal velocities of the E and A waveforms of ventricular filling. In normal fetuses, E/A ratios are usually <1 but show a constant increment during gestation, mainly related to the increment of the E wave. In intrauterine growth restriction (IUGR) fetuses, E/A ratios are lower compared to values in normally grown fetuses at the same gestational age. Cardiac outflows provide information on the time-velocity integral that, combined with the vessel area, allows calculation of the left and right cardiac outputs. In normal fetuses there is a predominance of the right ventricle (55-60%) in contributing to the combined cardiac output. In IUGR fetuses this predominance shifts to the left ventricle in order to increase the flow to the upper part of the fetal body and brain. The myocardial performance index (MPI) also provides information on systolic and diastolic cardiac function. The MPI is an early and consistent marker of cardiac dysfunction which becomes altered in early stages of chronic hypoxia or in cases with cardiac overload such as in twin-to-twin transfusion syndrome.

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.

Is fetal cardiac function gender dependent?

INTRODUCTION

An increased nuchal translucency (NT) is more common in males. A delayed diastolic cardiac function maturation has been proposed to explain this and the reported gender-related differences in ductus venosus (DV) flow.

OBJECTIVE

To investigate gender-related differences in fetal cardiac function.

METHODS

One hundred and ninety karyotypically/phenotypically normal fetuses with structurally normal hearts and known NT measurement, (104 > 95th percentile), were prospectively included between 1 October 2003 and 1 April 2009. They had been referred for fetal echocardiography. Three hundred and nine echocardiograms were performed between 11 and 35 weeks' gestation. The atrioventricular valve E- and A-wave peak velocity, E/A-velocity ratio and E/TVI ratio, myocardial performance index, semilunar valves acceleration time (AT) and peak velocity, stroke volume and cardiac output as well as DV pulsatility index for veins at 11-14 weeks' gestation, were measured. A multilevel analysis was performed using the NT (multiples of the median) as a continuous variable.

RESULTS

The male : female ratio was 1.56:1. The tricuspid valve E/TVI was significantly higher and pulmonary valve AT significantly lower in females compared to males. No other significant differences in cardiac function were found.

CONCLUSIONS

Our findings suggest better right ventricular (RV) relaxation and increased RV afterload in female fetuses, independent of NT thickness, between 11 and 35 weeks' gestation.

Cardiac function in trisomy 21 fetuses

OBJECTIVES

Trisomy 21 is associated with an increased nuchal translucency thickness (NT), abnormal ductus venosus (DV) flow at 11-14 weeks' gestation and congenital heart defects (CHD), and cardiac dysfunction has been hypothesized as the link between them. We therefore aimed to investigate whether cardiac function is altered in trisomy 21 fetuses.

METHODS

Between December 2003 and June 2009, we performed echocardiography on 46 trisomy 21 fetuses (28 with structurally normal heart and 18 with CHD) and on 191 chromosomally/phenotypically normal fetuses with a confirmed normal heart (87 with normal NT and 104 with NT ≥ 95(th) percentile), between 11 and 35 weeks' gestation. Measurements included: E- and A-wave peak velocity, E/A velocity ratio and E/time velocity integral (TVI) ratio over atrioventricular valves; myocardial performance index (MPI); semilunar valve peak velocity and acceleration time; stroke volume (SV); cardiac output; and DV pulsatility index for veins (PIV) at 11-14 weeks' gestation. Data were categorized into three different age groups for analysis (11 to 13 + 6, 14 to 21 + 6 and 22 to 35 weeks' gestation).

RESULTS

The tricuspid valve (TV) A-wave velocity and aortic valve peak velocity were significantly reduced in trisomy 21 compared with normal fetuses. Other highly significant differences found in trisomy 21 fetuses at 11-14 weeks' were increased TV-E/A ratio and DV-PIV, and decreased pulmonary valve peak velocity. We also observed evidence of left ventricular (LV) systolic dysfunction, reduced SV and increased MPI. After 14 weeks' gestation, the mitral valve A-wave peak velocity and E/TVI ratio were significantly reduced in the trisomy 21 fetuses with normal hearts compared with the controls with increased NT.

CONCLUSIONS

In comparison with controls with normal or increased NT, cardiac function in trisomy 21 fetuses is abnormal irrespective of the presence of CHD. Evidence for cardiac loading (increased preload and afterload) and LV systolic (in the first trimester) and later diastolic dysfunction was observed.

Fetal cardiac function between 11 and 35 weeks' gestation and nuchal translucency thickness

OBJECTIVES

The pathophysiological background of an increased nuchal translucency (NT) is still poorly understood. Cardiac dysfunction has been proposed as a cause. The aim of this study was to determine if, in fetuses with normal hearts, the NT thickness is related to cardiac function throughout gestation.

METHODS

The NT was measured in 191 karyotypically/phenotypically normal fetuses with structurally normal hearts and was increased (≥ 95(th) centile) in 104. All fetuses had been referred for fetal echocardiography and were prospectively included between October 1 2003 and April 1 2009. Three-hundred and ten echocardiograms were performed between 11 and 35 weeks' gestation. The E- and A-wave velocity, E/A velocity ratio, E/time velocity integral (TVI) ratio over the atrioventricular (AV) valves, myocardial performance index, acceleration time (AT) and peak velocity over the semilunar valves, stroke volume (SV) and cardiac output (CO) as well as the ductus venosus pulsatility index for veins at 11-14 weeks' gestation (DV-PIV), were measured. A multilevel analysis was performed using the NT multiples of the median (MoM) as a continuous variable.

RESULTS

AV-E- and A-wave velocities, E/A velocity ratios, semilunar valve peak velocity, SV, CO and aortic valve (AoV) AT increased significantly with advancing gestation. At 11-14 weeks' gestation, the AoV-AT, tricuspid valve (TV)-E/A, TV-E/TVI ratios and DV-PIV increased, and the pulmonary valve (PV) AT decreased, with increasing NT-MoMs. After midgestation, the PV-AT increased and the AoV-AT, TV-E/A and TV-E/TVI ratios decreased with increasing NT-MoMs.

CONCLUSIONS

NT thickness is related to right ventricular diastolic function and semilunar valve AT. Our findings suggest improved first-trimester, but later reduced, right ventricular relaxation and discordant ventricular afterload in fetuses with an increased NT.

Reference values for variables of fetal cardiocirculatory dynamics at 11-14 weeks of gestation

OBJECTIVE

Despite the increasing popularity of first-trimester fetal echocardiography, the evaluation of fetal heart function during this period remains challenging. The parameters of normal cardiac function at 11-14 weeks' gestation are not well defined and appropriate reference values have not yet been established. The purpose of this study was to evaluate the fetal cardiocirculatory dynamics during routine first-trimester screening and establish cross-sectional reference ranges for 11-14 weeks' gestation.

METHODS

Fetal echocardiography was performed on 202 women with singleton pregnancies at 11 + 0 to 13 + 6 weeks' gestation. Global cardiac function was evaluated using the heart : chest area ratio and Tei index of the left (LV) and right (RV) ventricles. The proportion of isovolumic contraction (ICT%) and ejection (ET%) times of the cardiac cycle, and the outflow velocities described the systolic function. Diastolic function was evaluated by the proportion of relaxation (IRT%) and filling (FT%) times, the ratio of the blood velocity through the atrioventricular valves during early filling (E) and atrial contraction (A) phases of the cardiac cycle, and ductus venosus pulsatility index for veins (DV-PIV). All participants had additional fetal echocardiography in the second trimester and neonatal clinical examination after birth to confirm normality.

RESULTS

The mean heart : chest area ratio (0.203 +/- 0.04) and the Tei indices of both ventricles did not vary significantly during weeks 11-14, but the mean Tei index of the LV (0.375 +/- 0.092) was significantly higher than that of the RV (0.332 +/- 0.079) (P = 0.001). The fetal heart rate (FHR) decreased with increasing crown-rump length (CRL) (P < 0.00001). The LV-ICT% did not vary significantly (P = 0.27), LV-IRT% (P = 0.03) and LV-ET% decreased (P = 0.01), whereas the LV-FT% increased (P = 0.02) with CRL. The RV-ET% (P = 0.84) and RV-FT% (P = 0.60) remained relatively stable. The LV-ET% was lower than the RV-ET% (P = 0.0001). The LV (P = 0.004) and RV (P < 0.00001) outflow velocities and E : A ratios of both ventricles (P < 0.0001) increased with advancing gestation. The E-velocity of the LV (P = 0.003) and RV (P = 0.002) increased significantly but the increase in A-velocity was not significant. The outflow velocity (P = 0.008) and E-velocity (P = 0.005) of the RV were higher than that of the LV but the A-velocities were similar (P = 0.066). The mean DV-PIV was 0.97 +/- 0.23 and did not change significantly (P = 0.95) during weeks 11-14. The FHR and DV-PIV did not correlate with the Tei index of either ventricle.

CONCLUSION

We have established reference ranges for the noninvasive evaluation of fetal cardiocirculatory dynamics at 11-14 weeks' gestation.

Profiling fetal cardiac function in twin-twin transfusion syndrome

OBJECTIVES

Cardiomyopathy in the recipient twin is a marker of severity in twin-twin transfusion syndrome (TTTS), making it a potentially valuable tool for staging the disease. This study aimed to provide a quantitative description of cardiac function in the recipient twin.

METHODS

Consecutive monochorionic pregnancies complicated with TTTS and treated by percutaneous laser coagulation underwent fetal echocardiography before surgery. An unsupervised classification analysis was conducted to identify groups of twins with similar cardiac profiles. The predictive value of the recipient twin's preoperative cardiac function based on these profiles was assessed, using perinatal death of at least one twin as the main outcome. The cardiac function profiles that we identified were compared with the current Quintero staging.

RESULTS

A total of 107 pregnancies were included, with six of these lost to follow-up; 63/107 complete cases were available for multivariate description of the recipient's cardiac function. Three different preoperative cardiac profiles were identified with increasing right and left myocardial performance index, decreasing right and left shortening fraction, and increasing ductus venosus pulsatility index. Although the three groups represented progressive stages of the syndrome-related cardiomyopathy, no correlation was found with pregnancy outcome. Of Quintero Stage 1 cases, 55% showed significant alterations of cardiac function in the recipient twin.

CONCLUSIONS

Progressive cardiomyopathy can be assessed quantitatively in the recipient twin and does not influence pregnancy outcome when fetoscopic laser coagulation is the first-line treatment. Compared with the current staging, cardiac profiling allows discrimination of cases with significant myocardial dysfunction.

Validation of the fetal myocardial performance index in the second and third trimesters of gestation

OBJECTIVES

To test the validity of the myocardial performance index (MPI) and its components against the more conventional methods of fetal cardiac function assessment: the ejection fraction (EF) for systolic function and the E/A index (ratio of transmitral flow during early (E) ventricular filling to flow during atrial (A) contraction) for diastolic function, both in a normal population and in a population at risk for cardiac failure because of volume overload (recipient fetuses in cases of twin-twin transfusion syndrome (TTTS)).

METHODS

The MPI was measured prospectively in addition to more commonly used indices of systolic (EF) and diastolic (E/A index) cardiac function in 117 healthy fetuses (gestational age range, 20-36 weeks) and in 14 fetuses suspected of cardiac failure because of the presence of TTTS. Nomograms were constructed for all variables, and correlations between the MPI, EF and E/A index were assessed. The time taken to obtain the measurements as well as the interobserver and intraobserver variability were determined for the MPI and EF.

RESULTS

In healthy fetuses, the MPI and EF were independent of gestational age, whereas the E/A index and isovolumetric relaxation time (IRT) increased with gestational age. The MPI correlated inversely with the EF (P<0.001). The IRT showed a trend towards an inverse correlation with the E/A index (P=0.10). The mean+/-SD time needed to measure the MPI and EF was 140+/-65 s and 185+/-187 s, respectively (P=0.43). Interobserver and intraobserver intraclass correlation coefficients for the MPI were 0.98 (95% CI, 0.85-0.99) and 0.82 (95% CI, 0.14-0.95), respectively; those for the EF were 0.58 (95% CI, -0.16 to 0.85) and 0.51 (95% CI, -0.46 to 0.83), respectively; and those for the E/A index were 0.97 (95% CI, 0.88-0.99) and 0.91 (95% CI, 0.66-0.98), respectively. All variables, except ejection time, were significantly different between normal fetuses and those with TTTS.

CONCLUSIONS

The MPI is an indicator of the systolic component of fetal left ventricular function that can be easily acquired and reproduced. The MPI is strongly correlated with the EF but shows less interobserver and intraobserver variability.

Modified myocardial performance index for evaluation of fetal cardiac function in pre-eclampsia

OBJECTIVE

To assess cardiac function by means of the modified myocardial performance index (Mod-MPI) in fetuses of pre-eclamptic mothers without intrauterine growth restriction and to compare this with values from normal controls.

METHODS

A cross-sectional study was conducted including a total of 72 fetuses at between 26 and 40 weeks' gestation. Forty fetuses of healthy mothers were assigned as the control group (Group I) while 15 fetuses of mildly pre-eclamptic mothers constituted Group II and 17 fetuses of severely pre-eclamptic mothers constituted Group III. Two-dimensional gray-scale and Doppler fetal echocardiography was used to exclude cardiac anomalies and calculate the Mod-MPI.

RESULTS

The mean+/-SD Mod-MPI values of Groups I, II and III were 0.43+/-0.045, 0.44+/-0.064 and 0.44+/-0.064, respectively (P=0.680). The mean aortic peak systolic velocity (PSV), the mean mitral valve early ventricular filling (E-wave) and active atrial filling (A-wave) peak velocities were significantly lower in fetuses of severely pre-eclamptic mothers than in fetuses of mildly pre-eclamptic mothers and control fetuses.

CONCLUSION

The fetal global myocardial function assessed by Mod-MPI does not seem to change in mild or severe pre-eclampsia. The lower mitral E-wave and A-wave peak velocities and the lower aortic PSV seem to reflect the increased cardiac afterload against which the fetal heart has to work, rather than systolic or diastolic cardiac dysfunction, in the fetuses of severely pre-eclamptic mothers.

Comparison between pulsed-wave Doppler- and tissue Doppler-derived Tei indices in fetuses with and without congenital heart disease

OBJECTIVES

The aim of this study was to compare the right (RV) and left (LV) ventricular Tei indices obtained by pulsed-wave Doppler (PD) and tissue Doppler (TD) methods in fetuses with structurally normal and abnormal hearts.

METHODS

This was a retrospective cross-sectional study of 147 fetuses that had a fetal echocardiogram and Tei index measured during a 2-year period. The RV and LV Tei indices were measured using both PD and TD methods. The difference between the two methods of Tei index measurement was tested using paired sample t-test, Pearson correlation coefficient was used to examine their relationship, and the agreement between the methods was tested using Bland-Altman analysis.

RESULTS

A total of 87 fetuses had normal hearts and 60 had a congenital heart defect. Both PD and TD Tei indices were measured successfully from at least one ventricle in 123 cases and from both ventricles in 110 cases. The mean TD Tei index was significantly higher than the mean PD Tei index for both ventricles (P < 0.0001). There was a weak but statistically significant correlation between the PD and TD Tei indices of the right ventricle (r = 0.20, P = 0.029), whereas the PD and TD Tei indices of the left ventricle did not correlate significantly (r = 0.04, P = 0.684). When pairs of Tei indices measured by two different methods (123 pairs for the right ventricle and 111 for the left ventricle) were tested with Bland-Altman analysis, the bias and precision were 0.147 and 0.254, respectively, for the right ventricle, and 0.299 and 0.276, respectively, for the left ventricle.

CONCLUSIONS

Correlation between Tei indices measured by PD and TD methods is weak and the agreement between individual measurements is poor. Therefore, they should not be used interchangeably in the assessment of fetal cardiac function.

Myocardial performance index during rapidly changing loading conditions: impact of different tidal ventilation

BACKGROUND AND OBJECTIVES

The myocardial performance index is a non-geometric, heart rate-independent echocardiography-derived index of left ventricular performance combining systolic and diastolic function. There is an ongoing debate whether the myocardial performance index is affected by preload or not. Moreover, a systematic evaluation of the effect of changing tidal volume ventilation on the myocardial performance index is still lacking. The aim of our study was to assess whether acute changes in preload and/or different depth of tidal volume ventilation affect the myocardial performance index.

METHODS

In all, 14 anesthetized pigs (35 +/- 2 kg) were studied during changing tidal volumes (VT 5, 10 and 15 mL kg(-1)) at baseline, after removal of 500 cm(3) of blood (haemorrhage) and after retransfusion of shed blood plus additional 500 cm(3) 6% hydroxyethyl starch (fluid loading). Echocardiographic measurements at each experimental stage included myocardial performance index, left ventricular end-diastolic area and fractional area change. Central venous pressure, pulmonary capillary wedge pressure, cardiac output and stroke volume index were obtained by a pulmonary artery catheter. Global end-diastolic volume was obtained by transpulmonary thermodilution.

RESULTS

Comparing different loading conditions, we found significant changes in cardiac output, stroke volume index, central venous pressure, pulmonary capillary wedge pressure, global end diastolic volume and left ventricular end-diastolic area, indicating clinically relevant changes in preload. In the haemorrhage group, there was a significant reduction in the myocardial performance index (P < 0.05) independent of tidal volume applied and this was reversed after fluid loading. However, myocardial performance index was significantly impaired (P < 0.05) by high tidal volume ventilation (15 mL kg(-1)), while tidal volumes of 5 and 10 mL kg(-1) had no effect.

CONCLUSIONS

The myocardial performance index is largely dependent on changes in preload. Moreover, high tidal volume ventilation significantly impaired the myocardial performance index.

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

OBJECTIVES

In the fetus with a structurally normal heart, two conditions--giant chest mass, such as congenital cystic adenomatoid malformation (CCAM), and twin-twin transfusion syndrome (TTTS)--alter ventricular loading conditions and may result in cardiovascular compromise. The aim of this study was to elucidate the mechanism of cardiovascular dysfunction by comparing geometry-independent, Doppler flow-derived measures of ventricular performance in fetuses with altered loading conditions vs. those in normal fetuses.

METHODS

Doppler flow-derived measures of myocardial performance index (MPI) as described by Tei, ventricular ejection force as described by Isaaz, and combined cardiac output (CCO) were obtained by echocardiography in fetuses with a normal cardiovascular system (n = 76) or CCAM (n = 36) and fetal partners with TTTS (n = 22).

RESULTS

In the CCAM group, systolic performance as evidenced by the ejection forces was preserved, right ventricular (RV) MPI was increased and CCO diminished, suggesting diastolic dysfunction and poor filling secondary to cardiac compression and a tamponade effect. In TTTS, recipient twins exhibited greater left ventricular (LV) ejection forces and higher CCO than donor twins, and had abnormal RV and LV MPI, reflecting increased preload, preserved left systolic performance, but diastolic dysfunction. Donor twins had diminished ejection forces and CCO in comparison with normal controls and recipient partners, reflecting hypovolemia.

CONCLUSIONS

In both CCAM and recipient twins of the TTTS, diastolic dysfunction plays a significant role in the pathophysiology of each disorder and precedes changes in systolic performance. Measures of ventricular performance can help elucidate poorly understood mechanisms of cardiovascular compromise in the developing fetus.

Fetal myocardial performance in pregnancies complicated by gestational impaired glucose tolerance

OBJECTIVE

To determine fetal myocardial performance in pregnancies complicated by mild gestational impaired glucose tolerance (GIGT).

METHODS

Ultrasound examinations were performed in 37 pregnant women with mild GIGT (36 did not require insulin) and in 44 controls at 18-24, 26-30 and 34-37 weeks of gestation. The thickness of the fetal ventricular walls and interventricular septum were measured by M-mode echocardiography. Using conventional Doppler echocardiography, the mitral and tricuspid early (E) and late (A) diastolic velocities and the ventricular myocardial performance index (MPI) were determined.

RESULTS

The fetuses of women with GIGT had a greater abdominal circumference (P = 0.02), a larger amniotic fluid index (P = 0.03), and a tendency to be heavier (P = 0.058) at the third scan. There were no significant differences in myocardial thickness, mitral and tricuspid E and A velocities, and E/A ratios between study and control groups. The left and right ventricular MPIs, while similar between the two groups in the first and second scans, had decreased significantly by late gestation in the GIGT fetuses (P for trend = 0.018 and 0.014, respectively) and were significantly lower than those of the control group (P = 0.002 and 0.0008, respectively).

CONCLUSIONS

Fetuses of women with mild GIGT lack the ventricular hypertrophy and diastolic dysfunction that is common in fetuses of diabetic mothers, and they have a decreased MPI late in gestation. Published by John Wiley & Sons, Ltd.

Gestational-age-adjusted reference values for the modified myocardial performance index for evaluation of fetal left cardiac function

OBJECTIVE

It has been shown that the modified myocardial performance index (Mod-MPI) is associated with higher reproducibility than conventional MPI because it uses mitral and aortic valve 'clicks' to calculate each time period. We aimed to construct normal reference values for the Mod-MPI after 19 weeks' gestation.

METHODS

The Mod-MPI was calculated in the left ventricle of 557 normal fetuses at 19-39 weeks' gestation. The isovolumetric contraction time (ICT), isovolumetric relaxation time (IRT) and ejection time (ET) were measured using the Doppler signals (clicks) of the opening and closing of the mitral and aortic valves as landmarks. Mod-MPI was calculated as (ICT + IRT)/ET.

RESULTS

Throughout gestation, there was a small increase in the Mod-MPI (at 19 weeks it was 0.35 +/- 0.027 (mean +/- SD); at 39 weeks, 0.37 +/- 0.029; Mod-MPI = 0.33 + 0.001x gestational age (GA) (weeks), r(2) = 0.017). Of the three components, ICT remained constant, IRT increased (IRT = 0.028 + 2.52 x GA (weeks)), and ET slightly decreased (ET = 0.184 - 3.65 x GA (weeks)). Fetal heart rate (FHR) had no effect on the Mod-MPI, but the duration of IRT, ICT and ET decreased by 13-15% when FHR increased from 130 to 160 beats per minute.

CONCLUSION

The GA-adjusted reference values for the Mod-MPI and the three time periods used for its calculation can be applied to fetal cardiac evaluation in the presence of pregnancy-associated complications.

Effects of modulation of left ventricular contractile state and loading conditions on tissue Doppler myocardial performance index

The Tei index is clinically useful to quantify left ventricular (LV) function, but it requires sequential Doppler recordings from two different views. A related myocardial performance index (MPI) using tissue Doppler (TD) can be rapidly calculated from a single beat; however, its ability to quantify contractility and the effects of acute changes in loading have not been determined. Our aim was to test the hypothesis that TD MPI can quantify contractile state but is affected by acute alterations in loading, using LV pressure-volume relations in an animal model. Eight dogs were studied by using mitral annular TD, high-fidelity pressure, and conductance catheters. TD MPI was calculated as (a' - b')/b', where a' was the duration of mitral annular velocity during diastole and b' was the duration of the systolic wave. End-systolic elastance (Ees), the time constant of isovolumic relaxation (tau), and peak positive and negative first derivative of pressure (dP/dtmax and dP/dtmin, respectively) were used as measures of LV function. Data were obtained at baseline, at dobutamine and esmolol infusion to alter contractile state, and at inferior vena cava and aortic occlusion to alter preload and afterload. TD MPI decreased from 0.83 (SD 0.19) to 0.62 (SD 0.20) with dobutamine and increased to 1.19 (SD 0.26) with esmolol. TD MPI significantly correlated with dP/dtmax (r = -0.76), Ees (r = -0.68), dP/dtmin (r = 0.82), and tau (r = 0.78); however, it was affected by acute decreases in preload [from 0.83 (SD 0.19) to 1.09 (SD 0.36)] and acute increases in afterload [to 1.23 (SD 0.17)]. All the above increases and decreases and r values were significant (P < 0.05 vs. baseline). In conclusion, TD MPI can rapidly quantify alterations in LV contractile state but is affected by acute alterations in preload and afterload.

A modified myocardial performance (Tei) index based on the use of valve clicks improves reproducibility of fetal left cardiac function assessment

OBJECTIVE

To determine whether a modified myocardial performance index (Mod-MPI) involving assessment of the movements (clicks) of the mitral valve (MV) and aortic valve (AV), improves intra- and interobserver agreement as compared to the previously reported method for MPI estimation.

METHODS

The Mod-MPI was recorded by two experienced operators in the left cardiac chambers of 25 normally grown fetuses using pulsed Doppler ultrasonography. The isovolumetric contraction time (ICT) was measured from the closure of the MV to the opening of the AV, the ejection time (ET) from the opening to the closure of the AV, and the isovolumetric relaxation time (IRT) from the closure of the AV to the opening of the MV. The Mod-MPI was calculated as (ICT + IRT)/ET. In addition, the MPI was estimated without using the valve clicks (F-MPI) as previously described. Intra- and interobserver agreement were then analyzed for both modalities.

RESULTS

There was a significantly lower intra- and inter-observer variability in the estimation of all time periods with the Mod-MPI than with the F-MPI (ICT: intra-observer, 9.9% vs. 13.9%; interobserver 9.9% vs. 15.6%; IRT: intraobserver, 9.9% vs. 14.8%; interobserver 10.4% vs. 18.3%; and ET: intraobserver, 4.5% vs. 6.1%; interobserver 2.8% vs. 5.2%, respectively). Intraclass correlation coefficient (IntraCC) for the Mod-MPI was 0.8 (95% confidence interval (95% CI), 0.56-0.9) and for the F-MPI, the IntraCC was 0.62 (95% CI, 0.26-0.84); P = 0.01. Agreement between observers using the Mod-MPI showed a mean difference of 0.0 with 95% limits of agreement (LA) -0.09 (95% CI, -0.1 to -0.075) to 0.09 (95% CI, 0.075-0.1) and for the F-MPI the mean difference was -0.01 with 95% LA -0.26 (95% CI, -0.3 to -0.22) to 0.25 (95% CI, 0.21-0.29).

CONCLUSION

Calculation of the Mod-MPI based on Doppler echoes of the MV and AV clicks is associated with a lower variation and better inter- and intraobserver agreement than the previously used method for fetal cardiac evaluation.

Early Intertwin Differences in Myocardial Performance During the Twin-to-Twin Transfusion Syndrome

Background— In the twin-to-twin transfusion syndrome (TTTS), pressure rather than volume overload is increasingly considered as a key factor in the pathogenesis of the cardiomyopathy of the recipient twin. If this is the case, cardiac dysfunction should be among the first signs observed with TTTS. The objective of this study was to determine whether intertwin differences in myocardial function are modified early in the course of TTTS and whether they can help to differentiate this condition from intrauterine growth restriction (IUGR).

Methods and Results— Eight variables were analyzed on the first fetal echocardiography on 21 pairs of twins with TTTS and 11 with IUGR. No difference was found between the 2 groups for the cardiothoracic ratio, pulsatility indices in the umbilical and middle cerebral arteries, and peak velocity of the middle cerebral artery. Significant difference was found for ventricular septal thickness, but with no association with the conditions under study. With TTTS, left ventricular shortening fraction was consistently greater in the donor twins, and myocardial performance indices (MPIs) were elevated in the recipient twins. This increase in MPI was caused by a lengthening of the isovolumic periods compared with those of the donor twin: left ventricular and right ventricular isovolumic periods 0.105±0.047 and 0.097±0.026 seconds, respectively, for the recipient twins versus 0.0561±0.46 and 0.065±0.03 seconds, respectively, for the donor twins ( P <0.001). These changes in the isovolumic periods were mainly due to significant prolongation of isovolumic relaxation times. A change in left ventricular MPI ≥0.09 combined with a change in right ventricular MPI ≥0.05 would identify a TTTS with a sensitivity of 75% and a false-positive rate of 9%.

Conclusions— The observed diastolic function impairment goes along with the pressure-overload pathogenic concept proposed in TTTS. Assessment of intertwin difference in MPI is a valuable tool for early differential diagnosis between TTTS and isolated IUGR.