Fetal Speckle-Tracking: Impact of Angle of Insonation and Frame Rate on Global Longitudinal Strain

doi:10.1016/j.echo.2020.03.013

Journal of the American Society of Echocardiography

Volume 33, Issue 9, September 2020, Pages 1141-1146.e2

https://doi.org/10.1016/j.echo.2020.03.013 Get rights and content

Highlights

•
Angle of insonation and frame rate influence strain measurements in the fetus.
•
Defining normal/pathologic fetal strain must consider insonation angle and frame rate.
•
2D strain is not an angle-independent measure of myocardial deformation in the fetus.

Background

There is a growing body of research on fetal speckle-tracking echocardiography because it is considered to be an angle-independent modality. The primary aim of this study was to investigate whether angle of insonation and acquisition frame rate (FR) influence left ventricular endocardial global longitudinal peak strain (GLS) in the fetus.

Methods

Four-chamber views of 122 healthy fetuses were studied at three different angles of insonation (apex up/down, apex oblique, and apex perpendicular) at high and low acoustic FRs. GLS was calculated, and a linear mixed-model analysis was used for analysis. Six hundred fifty-six fetal echocardiographic clips were analyzed (288 in the second trimester, at a median gestation of 21 weeks [interquartile range (IQR), 1 week], and 368 in the third trimester, at a median gestation of 36 weeks [IQR, 2 weeks]).

Results

Angle of insonation and FRs were significant determinants of GLS. Ventricular septum perpendicular to the ultrasound beam was associated with higher (more negative) GLS compared with apex up/down (at high FR: −21.8% vs −19.7%, P < .001; at low FR: −24.1% vs −21.4%, P < .001). Higher frames per second (FPS; median 149 FPS [IQR, 33 FPS] = 61 frames per cycle [FPC] [IQR, 17 FPC]) compared with lower FPS (median 51 FPS [IQR, 15 FPS] = 22 FPC [IQR, 7 FPC]) at the same insonation angle resulted in lower GLS (apex up/down: −19.7% vs −21.4%, P < .001; apex oblique: −21.2% vs −22.7%, P < .001; apex perpendicular: −21.8% vs −24.1%, P < .001).

Conclusions

The present findings show that insonation angle and FR influence GLS significantly. These factors need to be considered when comparing studies with different acquisition protocols, when establishing normative values, and when interpreting pathology. Speckle-tracking echocardiography cannot be considered an angle-independent modality during fetal life.

Section snippets

Methods

The study was conducted at a tertiary fetal cardiology service from September 2018 to September 2019. During this time, two-dimensional B-mode clips of the four-chamber view of fetuses without structural abnormalities in the second (19–27 weeks' gestation) or third (>28 weeks’ gestation) trimester were recorded as part of an advanced cardiovascular study (IRAS ID 237936, REC REF 18/NI/0013). All pregnant women provided written informed consent.

Results

For speckle-tracking analysis, a total of 656 clips of 122 healthy fetuses were recorded. Six clips per fetus (an example is illustrated in Figure 1) were available in 76 fetuses, five clips in 16 fetuses, and four clips in 30 fetuses.

The median gestational age for all clips was 30 weeks (IQR, 14 weeks). Fetuses in the second trimester accounted for 43.9% of clips (median gestational age, 21 weeks; IQR, 1 week), and 56.1% were obtained from fetuses in the third trimester (median gestational

Discussion

This study demonstrates that fetal speckle-tracking is not angle independent. Analysis of left ventricular GLS yielded increased deformation values when the apex of the heart was perpendicular to the ultrasound beam compared with the other positions (i.e., apex up/down or oblique). In addition, consistent with previous studies,¹⁰ we demonstrated that FR has a significant impact on GLS values. Using a FR of ≥40 FPC, as recommended,⁸ resulted in significantly lower GLS compared with lower FRs. As

Conclusion

This study has demonstrated that both the angle of insonation and FR have a significant impact on fetal speckle-tracking values. Contrary to the previous assumptions, speckle-tracking in fetal life cannot be considered an angle-independent method. In the future, it is therefore crucial to report both the angle of insonation and FR and take these into consideration when interpreting and comparing studies with different acquisition protocols. Moreover, a more standardized protocol of acquisition

Acknowledgments

We are grateful to our fetal cardiology team for their assistance and to Canon Medical Systems for loaning the ultrasound systems for this study.

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Citation Excerpt :
The image acquisition FR crucially determines the reliability of STE-derived strain parameters. There are conflicting results regarding the impact of FR on the 2D-STE-determined LV global longitudinal strain.37,38 A recent study by Yodwut et al39 revealed that an FR of 3D-STE as low as 18 frames/sec reflects the myocardial strain as precisely as 2D-STE with a high FR.
Three-dimensional speckle-tracking echocardiography (3D-STE) has been increasingly used to quantify right ventricular (RV) function. However, direct comparisons of 3D-STE with cardiac magnetic resonance (CMR) imaging for evaluation of RV function are limited. This study aimed to test the feasibility and accuracy of 3D-STE for the quantification of RV volumes, ejection fraction (EF), and longitudinal strain in comparison with CMR imaging and to determine whether 3D-STE for RV strain is superior to two-dimensional (2D) STE in comparison with CMR imaging.
A total of 195 consecutive patients referred for both CMR imaging and echocardiography were studied. Right ventricular end-diastolic volume (RVEDV), RV end-systolic volume (RVESV), RVEF, and 3D RV longitudinal strain (3D-RVLS) of the free wall by 3D-STE and 2D-RVLS of the free wall by 2D-STE, were compared with CMR measurements. Pearson correlation and Bland-Altman analyses were used to assess the intertechnique agreement.
Right ventricular 3D-STE was feasible in 174 patients (89%). Right ventricular volumes and EF determined by 3D-STE strongly correlated with CMR values (RVEDV, r = 0.94; RVESV, r = 0.96; RVEF, r = 0.91; all P < .001). Three-dimensional STE slightly underestimated the RV volumes and longitudinal strain and overestimated the RVEF. The 3D-RVLS values correlated better than 2D-RVLS values with CMR values (0.85 vs 0.64, P < .001) with smaller bias and narrower limits of agreement (bias: 2.0 and 2.6; limits of agreement: 8.5 and 12.5, respectively). The bias and limits of agreement for 3D-STE-obtained RVLS were increased in patients with RV dilation, RVEF < 45%, or lower frame rate compared with those with normal RV size, RVEF ≥ 45%, or higher frame rate, respectively. Right ventricular 3D-STE measurements were highly reproducible.
The 3D-STE measurements of RV volumes, EF, and longitudinal strain are highly feasible and reproducible, and data measured by 3D-STE correlate strongly with those determined using CMR imaging. Thus, 3D-STE may be a valid alternative to CMR imaging for the quantification of RV function in everyday clinical practice.
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: This study was first presented in part in poster form during the Third Annual Meeting of the Association for European Paediatric and Congenital Cardiology, May 15–18, 2019, Seville, Spain.

: Conflicts of interest: None.

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2020 Published by Elsevier Inc. on behalf of the American Society of Echocardiography.

Fetal EchocardiographyFetal Speckle-Tracking: Impact of Angle of Insonation and Frame Rate on Global Longitudinal Strain

Highlights

Background

Methods

Results

Conclusions

Section snippets

Methods

Results

Discussion

Conclusion

Acknowledgments

Am J Obstet Gynecol

J Am Soc Echocardiogr

J Am Soc Echocardiogr

J Am Soc Echocardiogr

J Am Soc Echocardiogr

J Am Soc Echocardiogr

J Am Soc Echocardiogr

J Am Soc Echocardiogr

Using speckle-tracking echocardiography to assess fetal myocardial deformation: are we there yet?

Ultrasound Obstet Gynecol

Fetal myocardial deformation in maternal diabetes mellitus and obesity

Ultrasound Obstet Gynecol

Perinatal changes in cardiac geometry and function in growth-restricted fetuses at term

Ultrasound Obstet Gynecol

Experimental validation of a new ultrasound method for the simultaneous assessment of radial and longitudinal myocardial deformation independent of insonation angle

Circulation

Assessment of left ventricular global and regional longitudinal peak systolic strain, strain rate and velocity with feature tracking in healthy fetuses

Ultraschall Med

Two-dimensional speckle tracking of the fetal heart: a practical step-by-step approach for the fetal sonologist

J Ultrasound Med

Temporal and spatial performance of vector velocity imaging in the human fetal heart

Ultrasound Obstet Gynecol

Fetal Echocardiography
Fetal Speckle-Tracking: Impact of Angle of Insonation and Frame Rate on Global Longitudinal Strain