Speckle tracking analysis of the fetal heart in uncomplicated pregnancies and complicated pregnancies: a pilot study using FetalHQ

Abstract

Background: Strain imaging by speckle tracking echocardiography (STE) is a novel and promising ultrasound technique for a detailed evaluation of fetal cardiac function. It may contribute to the selection of high-risk patients with pregnancy complications affecting fetal hemodynamics and inducing fetal cardiac remodeling, such as maternal diabetes mellitus (DM) and placental pathologies with ensuing fetal growth restriction (FGR). STE is already used in adults and pediatrics, but is still under evaluation in fetal medicine. The aim of this pilot study is to substantiate the feasibility of FetalHQ, a newly developed speckle tracking software, and to determine normal values of fetal strain throughout pregnancy. Also, potential effects of maternal DM and FGR on fetal strain will be studied. Methods: Fetal STE was performed in uncomplicated pregnancies and pregnancies complicated by maternal DM or FGR. Dynamic cine loop clips of the fetal heart were collected during regular planned ultrasound examinations between 18-40 weeks of gestation. Global longitudinal strain values of the left ventricle (LV) and right ventricle (RV) were measured at each examination using offline software FetalHQ. Intra- and interobserver variability were estimated using intraclass correlation coefficient and Bland-Altman analysis. Linear mixed effect models were used to determine the development of fetal strain throughout gestation and potential effects of maternal DM and FGR on fetal strain. Mean strain values within 18-24 weeks, 25-31 weeks and 32-40 weeks of gestation were compared between study groups using independent-samples T-test and Mann-Whitney U test. Results: A total of 69 participants (101 clips) with uncomplicated pregnancies, 20 participants (46 clips) with pregnancies complicated by maternal DM and 18 participants (52 clips) with pregnancies complicated by FGR were included. Comparing examinations between observers showed moderate agreement for the LV and poor agreement for the RV, with significant differences in measurements between observers for both ventricles. Comparing repeated measurements of one observer showed good agreement for the LV and moderate agreement for the RV, with significant differences between repeated measurements of the RV only. Analysis of good quality clips only improved agreement between and within observers. Fetal strain in uncomplicated pregnancies showed a significant decrease with advancing pregnancy in both ventricles. No significant differences were observed between fetal strain in uncomplicated pregnancies and fetal strain in pregnancies complicated by maternal DM or FGR. Conclusion: This pilot study showed that the feasibility of speckle tracking analysis using FetalHQ is currently limited. Reliability and reproducibility of strain analysis should be improved by gaining experience with the analysis and standardizing the operative protocol, such as image acquisitions and angle of insonation, before implementation as a tool to evaluate fetal cardiac function.