2.1. Subjects
In this prospective study, a total of 136 unselected, normal singleton second and third trimester fetuses with normofrequent heart rate were examined during targeted ultrasound survey. All women were routinely investigated by application of Fetal Heart Quantification (fetalHQ®) between August 2021 and January 2024. The used cine-loop sequences were acquired and subsequently analyzed offline by a beginner (J.L.S.) and an expert operator (J.W.) based on consecutively, but independently recorded ultrasound images, and had to fulfill predefined in- and exclusion criteria. Fetuses with structural abnormal hearts and heart rate or clips with insufficient image clarity were excluded. The expert (J.W.) selected both the cine-loop clips recorded by the beginner (J.L.S.), as well as his own and confirmed their applicability for further analysis. It was ensured that the interventricular septum (IVS) had the same orientation between both operators. However, both performed the analysis blinded to each other. Informed consent was obtained from all participants. The measured endoGLS values were matched with those reported in the literature.