Evaluation of myocardial mechanics in the fetus by velocity vector imaging

There are limited data on the properties of fetal myocardium with only a small number of Doppler tissue imaging-based studies published. We evaluated the feasibility of using velocity vector imaging, a novel technique for analyzing 2-dimensional images offline, to study myocardial mechanics in the normal fetal heart at different of gestational ages. A single 2-dimensional 4-chamber image of the heart was interrogated offline using velocity vector imaging software. Longitudinal velocity, strain, and strain rate were measured in the right ventricular free wall, ventricular septum, and left ventricular free wall. Images from 24 of 27 (89%) were successfully analyzed. The systolic and diastolic longitudinal velocities increased with gestational age in all myocardial segments analyzed (r = 0.56-0.78, P < .05). Systolic strain and strain rate were not found to have significant correlation with gestational age in any of the wall segments. This implies that increasing velocities during normal gestation are the result of somatic growth rather than changes in myocardial contractility.