Measurement of Cardiac Contractility Using Fetal Isovolumetric Contraction Time in Fetal Tachyarrhythmia

The isovolumetric contraction time (ICT) is known to be an index of cardiac contractility. In this study, we examined the relationship between the fetal ICT and fetal heart rate (FHR) and evaluated the usefulness of ICT in the assessment of fetal cardiac contractility in cases with fetal tachyarrhythmia. Seven cases with fetal tachyarrhythmia between 32 and 40 weeks' gestation were included in this study. The fetal ICT was measured using a continuous Doppler device and digital filters. The relationship between the fetal ICT and FHR was analyzed using the Spearman's rank correlation test in each fetus. Based on the FHR and ultrasound findings of hydrops at the measurement of ICT, the obtained data were divided into three groups: normal, tachyarrhythmia only and hydrops. The clinical usefulness of ICT was assessed using the random effect model. In 7 fetuses, a total of 60 data points were obtained. A significant correlation between fetal ICT and FHR was not noted in each fetus. The ICT of the hydrops group was significantly prolonged compared with those of the normal and tachyarrhythmia-only groups (p < 0.01). An association between the fetal ICT and FHR is not noted and the fetal ICT might have some utility to detect impaired fetal cardiac contractility even in fetuses with tachyarrhythmia.