Left Ventricular Rotational and Twist Mechanics in the Human Fetal Heart

The authors investigated left ventricular (LV) rotational indices, twist, and torsion in a large cohort of fetuses using two-dimensional speckle-tracking echocardiography.

Pregnant women (N = 102) were prospectively recruited for fetal two-dimensional speckle-tracking echocardiography. Because of variable fetal position, ventricular orientation was established using the location of the liver and LV position in relation to the right ventricle. Twist measurements required correction to account for fetal position, reconciling directionality across all fetal orientations. Peak apical and basal rotations, global longitudinal strain, global circumferential strain (GCS), longitudinal strain rate, circumferential strain rate (CSR), twist, and torsion were reported and tested for associations with gestational age (GA) and estimated fetal weight (EFW).

Measurement of rotational indices was feasible in 175 examinations (73%). The mean maternal age was 31 ± 6 years, the mean GA 24 ± 6 weeks, and the EFW 1.0 ± 1.0 kg. Mean peak apical rotation, basal rotation, twist, and torsion were 9.5 ± 2.0°, -4.4 ± 1.1°, 13.1 ± 2.3°, and 7.9 ± 3.4°/cm, respectively. Mean global longitudinal strain, GCS, longitudinal strain rate, and CSR were -22.3 ± 4.3%, -25.0 ± 6.1%, -1.4 ± 0.5 sec^-1, and -1.6 ± 0.5 sec^-1, respectively. Absolute GCS, CSR, apical rotation, and twist declined moderately with GA and EFW (P < .05). There were strong negative nonlinear correlations of torsion with GA and EFW: torsion = 1,104 × GA^-1.591 (r² = 0.760, P < .001); torsion = 115.88 × EFW^-0.427 (r² = 0.772, P < .001).

Determination of fetal LV rotational mechanics is feasible and reproducible using two-dimensional speckle-tracking echocardiography. Basal rotation, longitudinal strain, and strain rate vary little with EFW and GA. Interpretation of LV apical rotation, twist, torsion, GCS, and CSR, however, must take GA or EFW into account. These data form the basis for comparison with findings in fetuses with abnormal cardiac anatomy and function.