Abstract

OBJECTIVE: Left ventricular (LV) torsion is an important aspect of cardiac mechanics and fundamental to normal ventricular function. The myocardial mechanics of the fetal heart and the transition to extrauterine life have not been explored previously. The aim of this study was to evaluate perinatal changes in LV torsion and its relationship to myocardial function. METHODS: A prospective study of 36 women with uncomplicated term pregnancies. Fetal and neonatal conventional, spectral tissue Doppler imaging, and 2D speckle tracking cardiac indices including LV rotation data derived in short axis views at the base and apex of the heart were obtained days before and within hours of birth. RESULTS: There are three patterns of LV twist in term fetuses, from the lowest values of torsion in reversed apex-type (0.1°/cm), through to higher values of infant-type (1.6°/cm) and to the highest values in adult-type LV twist (4.4°/cm). Patterns of fetal LV twist and torsion were also significantly associated with cardiac geometry and functional indices. Perinatal evaluation revealed a significant increase in LV torsion in fetuses exhibiting reversed apex-type LV twist (increased by 2.8°/cm, p=0.01) and a significant decrease in fetuses with adult-type LV twist (decreased by 3.2°/cm, p=0.008). CONCLUSIONS: This study demonstrates the feasibility of 2D speckle tracking imaging for accurate assessment of rotational cardiac parameters in term fetuses. There are unique perinatal patterns of LV twist that correlate to indices of ventricular geometry and myocardial function. Differences in patterns of LV twist may reflect different compensatory myocardial adaptation to the physiological environment/loading conditions of late gestation in fetuses and postnatal cardiac adjustment to the acute loading changes that occur at birth. This article is protected by copyright. All rights reserved.