Functional assessment of fetal heart: Normative data for tissue doppler indices and other echocardiographic parameters for Indian population

Anupama Nair; Sitaraman Radhakrishnan

doi:10.4103/jiae.jiae_55_17

ORIGINAL INVESTIGATION

Year : 2017 | Volume : 1 | Issue : 2 | Page : 103-108

Functional assessment of fetal heart: Normative data for tissue doppler indices and other echocardiographic parameters for Indian population

Anupama Nair¹, Sitaraman Radhakrishnan²
¹ Department of Fetal, Fortis Escorts Heart Institute, New Delhi, India
² Department of Pediatric Cardiology, Fortis Escorts Heart Institute, New Delhi, India

Date of Web Publication

28-Aug-2017

Correspondence Address:
Anupama Nair
5th Floor, Fortis Escorts Heart Institute, Okhla Road, New Delhi - 110 025
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jiae.jiae_55_17

Abstract

Objective: To establish normative data for tissue Doppler indices and other parameters for ventricular function assessment in fetal imaging for the Indian population and to assess the variation of these parameters with gestational age. Materials and Methods: A prospective study involving 172 fetuses diagnosed as having normal cardiac structure and function. Mothers were advised for fetal echocardiography for several indications; however, mothers with diabetes (both gestational and pregestational), placental dysfunction, fetuses with intrauterine growth retardation, and multiple gestation were excluded as these could affect the fetal cardiac function despite a normal cardiac structure. Peak myocardial velocity was measured during systole (S'), early diastole (E'), and late diastole (A') using spectral tissue Doppler. Pulsed Doppler was used to measure the inflow early (E) and late (A) diastolic velocities and the diastolic filling period (DFP). M-mode was used to measure the tricuspid and mitral annular peak systolic excursion (TAPSE and MAPSE). Results: Normative data for tissue Doppler velocities and various other parameters for functional assessment of fetal heart were derived from the 172 normal fetuses. On tissue Doppler imaging (TDI), the mean values for the peak systolic and diastolic velocities at the lateral and medial mitral annulus and at the lateral tricuspid annulus and ratio of early and late diastolic velocity (E'/A') increased while the (E/E') ratio decreased with gestational age. Other parameters that increased with age are TAPSE, MAPSE, and the DFP at the tricuspid and mitral valves. The left and right ventricular myocardial performance index did not show any variation with gestation. Conclusion: TDI has already been documented as a useful technique in fetal cardiac imaging. The normative data so derived for various parameters can be used as a future reference. These parameters can prove very useful in fetal cardiac functional evaluation and detection of systolic or diastolic dysfunction at an early stage which may have long-term and prognostic implications.

Keywords: Diastolic filling time, fetal cardiac function, fetal echocardiography, tissue Doppler imaging

How to cite this article:
Nair A, Radhakrishnan S. Functional assessment of fetal heart: Normative data for tissue doppler indices and other echocardiographic parameters for Indian population. J Indian Acad Echocardiogr Cardiovasc Imaging 2017;1:103-8

How to cite this URL:
Nair A, Radhakrishnan S. Functional assessment of fetal heart: Normative data for tissue doppler indices and other echocardiographic parameters for Indian population. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2017 [cited 2023 Jun 10];1:103-8. Available from: https://jiaecho.org/text.asp?2017/1/2/103/213678

Introduction

Assessment of fetal cardiac function on prenatal ultrasonography is challenging since detection of signs of fetal cardiac failure such as hydrops is very late features. Early detection of cardiac dysfunction is useful in monitoring pregnancy and planning delivery. Tissue Doppler imaging (TDI) though less commonly used in fetal cardiac evaluation can become an important modality for quantitative assessment of systolic and diastolic ventricular function. Being less load dependent,^[1] it is more suitable for fetal cardiac assessment since, in fetus, the loading conditions get easily affected by extracardiac factors such as changes in placental resistance. Although reference data for the Western population are available,^[1],[2],[3] the same for Indian population is not reported.

Aim

The aim of this study is to establish the normative data for tissue Doppler indices and other parameters for ventricular function assessment in fetal imaging for the Indian population and to assess the variation of these parameters with gestational age.

Materials and Methods

Study groups

This is a prospective observational study conducted at a tertiary referral center for pediatric cardiology in Northern India and involved 172 healthy pregnant women with singleton pregnancy whose fetuses were shown to have a normal echocardiogram. The study was performed over a duration of 1 year and included a population of mixed ethnicity and both rural and urban patients. These women were referred for fetal echocardiography due to various indications such as family history of congenital heart defect, abnormal cardiac images on ultrasound, maternal diabetes, multiple fetuses, advanced maternal age, or abnormal Doppler patterns on obstetric ultrasound. We excluded mothers with diabetes (both gestational and pregestational), placental dysfunction, fetuses with intrauterine growth retardation (IUGR), and multiple gestation as these could affect the fetal cardiac function despite a normal cardiac structure. We also excluded studies with insufficient data due to poor images.

Echocardiographic evaluation

All the studies were done on the Philips IE-33 system, and a detailed fetal echocardiographic evaluation was done. Simultaneously using a 5MHz transducer, various spectral Doppler measurements were done along with TDI measurements during the complete absence of fetal movements. All the measurements were made in the apical or basal four-chamber view using conventional pulsed wave Doppler and spectral (pulsed Doppler) TDI with a sample volume of 2 mm.

Tissue Doppler imaging

Low filters and higher sweep speed (100 cm/s) were used, and the frame rate was at least above 150 frames/s. TDI was performed only when an angle of insonation of <20° was achieved and no angle correction was used. Using the spectral TDI, peak myocardial velocities were measured during systole (S'), early diastole (E'), and late diastole (A'). Myocardial velocities were measured at the lateral tricuspid and mitral valve annuli and the medial mitral valve annulus (interventricular septum). The right and left ventricular myocardial performance index (MPI) and isovolumic relaxation times (IVRTs) were also measured from TDI [Figure 1].

Figure 1: Tissue Doppler trace demonstrating the various measurements

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Conventional pulsed wave Doppler

Pulsed wave Doppler was used for measuring the early (E) and late (A) diastolic inflow velocities at both tricuspid and mitral valves as well as for calculation of the ratio of early diastolic flow velocities to that of early diastolic myocardial velocity (E/E'). The diastolic filling period (DFP) for both left and right ventricles was calculated as the ratio of total diastolic filling time to the total duration of cardiac cycle. The total diastolic filling time was measured from the beginning of E-wave to the end of A-wave whereas the total duration of cardiac cycle was measured as the time between the beginning of one E-wave to the beginning of next E-wave including the E- and A-waves used to measure the total diastolic filling time.

We also measured the tricuspid annular peak systolic excursion (TAPSE) and the mitral annular peak systolic excursion (MAPSE) using the M-mode in the same apical view. Three successive measurements of all the parameters were obtained and averaged to get the final value.

Statistical analysis

Continuous variables are presented as mean ± standard deviation and unpaired Student's t-test was applied for normally distributed continuous variables. Pearson's correlation coefficients were calculated for assessing the relationship between gestational age and other echocardiographic parameters. Statistical significance was assumed at a value of P < 0.05. Statistical Package for the Social Sciences (SPSS– version 13) software (SPSS-Inc., Chicago, IL, USA) was used for the statistical analysis.

Results

The study included a total of 172 pregnant women referred to our center for fetal echocardiography between 16 and 37 weeks of gestation. Mean maternal age was 28.5 ± 4.7 years. Patients were divided into two groups according to the gestational age as the second and third trimester. Distribution of patients into each group is shown in [Table 1].

Table 1: Distribution of patients according to the gestational age

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Normative data were derived from the echocardiographic evaluation of these 172 normal fetuses. Mean fetal heart rate was 148 ± 7 in the second trimester and it decreased to 139 ± 5.7 in the third trimester. The PR interval was 116 ± 8 and did not show significant change with gestational age. TDI spectral velocities were obtained in all the 172 normal fetuses, and the mean values for the peak systolic and diastolic velocities at the lateral and medial mitral annulus and at the lateral tricuspid annulus are presented in [Table 2].

Table 2: Peak tissue Doppler spectral velocities (cm/s) during the second and third trimester presented as mean with standard deviation. Spectral tissue Doppler velocities at all sites increased with advancing gestation

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Other functional parameters measured included the right and left ventricular MPI or Tei index calculated from the tissue Doppler trace, MAPSE and TAPSE measured from M-mode, and the right and left ventricular DFP measured from pulsed Doppler trace of mitral and tricuspid inflows. [Table 3] represents the normative data for these indices.

Table 3: Normative data for other systolic and diastolic functional parameters

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When correlated with the gestational age, various parameters showed variable response with increasing gestation. On TDI, the mean values for the peak systolic (S') and early (E') and late (A') diastolic velocities at the lateral mitral annulus [Figure 2], the tricuspid annulus [Figure 3], and at the medial mitral annulus [Figure 4] increased with gestational age. The ratio of early and late diastolic myocardial velocities (E'/A') increased while the ratio of early inflow to early myocardial diastolic velocity (E/E') decreased with gestational age both at the tricuspid and mitral annulus [Figure 2] and [Figure 3]. The MPI and IVRT of both left and right ventricles did not show any significant variation with gestational age [Figure 5].

Figure 2: Relationship between gestational age and tissue Doppler velocities and M-mode at lateral mitral annulus. The tissue Doppler imaging early (E') and late (A') diastolic and systolic (S') velocities (panels a-c), E'/A' ratio (panel d) as well as mitral annular peak systolic excursion (panel e) increased progressively with gestational age. The E/E' ratio (panel f) showed a negative correlation and decreased with increasing gestation

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Figure 3: Relationship between gestational age and tissue Doppler velocities and M-mode at lateral tricuspid annulus. The tissue Doppler imaging early (E') and late (A') diastolic and systolic (S') velocities (panels a-c), E'/A' ratio (panel d) as well as tricuspid annular peak systolic excursion (panel e) increased progressively with gestational age. The E/E' ratio (panel f) showed a negative correlation and decreased with increasing gestation

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Figure 4: Relationship between gestational age and tissue Doppler velocities at interventricular septum. The tissue Doppler imaging early (E') and late (A') diastolic and systolic (S') velocities (shown in panels a, b, and c, respectively) increased progressively with gestational age

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Figure 5: Parameters that did not show any variation with gestational age. The myocardial performance index and isovolumic relaxation time of both left (panel a and b, respectively) and right (panel c and d, respectively) ventricles did not show any significant variation with gestational age

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Evaluation of the other parameters revealed that MAPSE [Figure 2] and TAPSE [Figure 3] increased with increase in gestation. On pulsed Doppler evaluation, the DFP of both right and left ventricles increased with increasing gestation and so did the mitral and tricuspid inflow early (E) and late (A) diastolic velocity ratio (E/A) [Figure 6].

Figure 6: Relationship between gestational age and pulsed Doppler parameters at the inflows. The mitral and tricuspid inflow early (E) and late (A) diastolic velocity ratio (E/A) in panels (a and b) showed a positive correlation with gestational age. The diastolic filling period of both right (c) and left (d) ventricles increased with increasing gestation

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Discussion

Our study demonstrates the normal values and the gestational age-related changes in the tissue Doppler-derived myocardial velocities and other parameters of ventricular function assessment in the fetus. All the tissue Doppler myocardial velocities (systolic S', early E', and late A' diastolic velocities) increased with gestational age at all the three sites, namely, lateral mitral and tricuspid annulus and the medial mitral annulus (interventricular septum). However, the absolute value of the velocities at interventricular septum was much lower than that of the lateral walls which is probably because the septum is coupled with right ventricular while the lateral wall is free. Although both the early (E') and late (A') diastolic velocities increased, simultaneous increase in the E'/A' ratio indicates a greater rise of early diastolic velocity (E') with age and supports the fact that it is an important index of myocardial maturation and ventricular diastolic function.^[2],[3],[4] The E/E' ratio showed a decrease with increasing gestational age due to improved myocardial relaxation and elastic recoil with myocardial maturation. This observation was similar to that of other studies.^[1],[5] The inflow velocities are markedly dependent on loading conditions which can get altered by changes in placental vascular resistance and therefore not necessarily reflect fetal myocardial dysfunction. Tissue Doppler has a major advantage over the inflow velocities as it measures the myocardial velocities which are more accurate and less load dependent.^[1] In addition, TDI also evaluates the systolic function. Larsen et al.^[6] has demonstrated that a decrease in the peak systolic myocardial velocity (S') is a predictor of perinatal mortality in fetuses with growth restriction and reversed umbilical artery flow.

MPI is a combined index of global myocardial function, and it is independent of ventricular size, geometry, and heart rate.^[7] The MPI of both right and left ventricle did not show any change with gestational age. Furthermore, the left ventricular MPI value obtained by tissue Doppler (0.42 ± 0.04) was similar to that obtained by pulsed Doppler (0.42 ± 0.03) in our previous study.^[7] This is in contrast to the findings of Acharya et al.^[8] who showed that MPI values by tissue Doppler were higher than the pulsed Doppler. Amoozgar et al.^[9] attributed this discrepancy between pulsed Doppler and TDI-derived MPI to the loading conditions which affected the pulsed Doppler values significantly. MPI is useful in detecting subtle ventricular dysfunction in fetuses with various diseased states such as IUGR, twin-twin transfusion syndrome, fetus of diabetic mother, and fetal inflammatory response syndrome in fetuses with preterm premature rupture of membranes.^[7]

The DFP calculated as the ratio of total diastolic inflow time to the total cardiac cycle time is a surrogate marker of ventricular compliance^[10] and end-diastolic pressure. This was nearly similar for the left and right ventricle. It showed a progressive increase with gestational age and indicated myocardial maturation and improvement of diastolic function with increasing gestation. A decreasing DFP indicates an increasing filling pressure and can impair the ventricular filling and consequently affect its development. Assessment of DFP can be useful in early identification of evolving right or left heart hypoplastic lesions. Nawaytou et al.^[11] measured the systolic to diastolic time index and reported that fetuses with evolving and overt hypoplastic left heart syndrome exhibited significantly increased values compared to normal fetuses. Similarly, Roman et al.^[10] in their study involving fetuses with pulmonary stenosis or atresia with intact interventricular septum showed that a tricuspid inflow duration of <31.5% of total cardiac cycle was one of the factors precluding biventricular outcome.

TAPSE and MAPSE are indicators of systolic function. Normally, TAPSE is greater than MAPSE and both increased with gestation. Pérez-Cruz et al.^[12] studied the fetal cardiac function in IUGR fetuses and showed that such fetuses showed signs of both systolic and diastolic dysfunction, with decreased longitudinal motion (measured by M-mode and tissue Doppler) even when the gross cardiac function appeared normal.

These parameters can prove very useful in fetal cardiac functional evaluation and detection of systolic or diastolic dysfunction at an early stage. TDI has been used for evaluation of the ventricular function in fetuses undergoing aortic valvuloplasty before and after the procedure by Wolhmuth et al.^[13] Parameters such as DFP already form a part of various scoring systems.^[10]

Limitations

This study has certain limitations. First, as tissue Doppler measurements are vendor specific,^[14] these values remain specific to Philips software. Second, the possibility of interobserver errors cannot be excluded from the study since all the observations were made by a single operator. Finally, the number of patients in the third trimester is small since ideal age for fetal cardiac evaluation is before 20 weeks. Although many patients are referred late,^[15] still greater part of them were referred within the second trimester.

Conclusion

TDI in fetal cardiac evaluation has already been shown to be a useful technique. We have attempted to create normative data for fetuses with structurally normal heart in our population group so that it can be used as a future reference. Although the exact clinical utility of TDI still remains uncertain, it can prove to be a useful quantitative tool to add to our cardiovascular profile score and may also prove to be of prognostic significance; however, it needs further studies for validation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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