This study aimed to determine the normal reference values and distribution of global longitudinal strain (GLS) in the right and left ventricles of healthy Japanese fetuses during pregnancy. This multi-institutional cohort study included healthy Japanese fetuses during normal pregnancies without maternal or fetal complications between 18 and 40weeks of gestation. Two-dimensional fetal echocardiographic images of the four-chamber view with a high frame rate were acquired and stored as DICOM clips. Data were collected and analyzed in a central laboratory to measure the left ventricular (LV) and right ventricular (RV) GLS using two-dimensional speckle tracking. In total, 513 fetuses were enrolled. The mean LV-GLS and RV-GLS were - 24.3% ± 3.5% and - 23.5% ± 3.7%, respectively. The magnitude of the GLS, with normal limits in both ventricles, decreased with advancing gestation. LV values were r = 0.34 (95% confidence interval, 0.27-0.42) and p < 0.0001; RV values were r = 0.33 (95% confidence interval, 0.25-0.41) and p < 0.0001. The normal values of healthy Japanese fetuses in healthy pregnancies is the first to be established by the large-scale, multi-institutional cohort study as LV-GLS of 24.3% ± 3.5% and RV-GLS of - 23.5% ± 3.7%, respectively. This can serve as a basic reference for assessing the cardiac functions in Japanese fetuses with various heart diseases.
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