Objectives: The velocity vector imaging (VVI) technique is useful to assess regional myocardial mechanics. The aim of this study was to evaluate the usefulness of this technology in assessing regional right ventricular longitudinal functions in the fetus and to establish a nomogram of the right ventricle (RV).
Methods: We studied 170 healthy fetuses that were divided into five groups based on gestational age. Dynamic digital images of four chambers were collected and analyzed off-line. The longitudinal VVI parameters were calculated in the right free wall and ventricular septum, respectively.
Results: A total of 151 out of 170 fetuses (89%) were successfully analyzed using VVI, with good inter- and intra-observer agreements. Normal values for velocity, strain, and strain rate were established. The tissue velocity gradually decreased from basal to apical segment (P < 0.05), whereas strain and strain rate remained stable. The tissue velocity increased with gestational age (P < 0.05), whereas strain and strain rate were stable (P > 0.05).
Conclusion: Fetal myocardial velocity, strain, and strain rate measurements are easy to obtain and are reproducible. From mid-to-late gestation, the longitudinal tissue velocity of the RV increases with gestational age, whereas strain and strain rate remain stable. These results indicate that myocardial contractility is established in mid-gestation and remains constant throughout gestation.