HEMODYNAMIC-CHANGES ACROSS THE HUMAN DUCTUS VENOSUS - A COMPARISON BETWEEN CLINICAL FINDINGS AND MATHEMATICAL CALCULATIONS

We investigated the hemodynamics of the ductus venosus in the human fe tus by means of a combined approach based on Doppler and computational techniques. The aim of our study was to assess the blood velocity cha nges across the ductus venosus. Color Doppler equipment was used to in vestigate 29 normal fetuses between 20 and 39 weeks of gestation. Velo cities at the systolic peak (S), diastolic peak (D) and atrial contrac tion (A) were measured at the isthmus and at the outlet of the ductus venosus, and the corresponding angle-independent indices (S/A, (S - A) /S, (S - A)/D) were calculated. A parametric computational model was d eveloped in order to investigate the influence of anatomical features of the ductus venosus on the hemodynamics of the vessel. In all the fe tuses the S, D and A velocities at the outlet portion were significant ly lower than those at the isthmic part of the ductus venosus (p < 0.0 001). The mean percentages of velocity reduction were 23.1%, 26.5% and 33.6%, respectively. Computational simulations also showed a relevant decrease of the velocity along the ductus venosus during the whole ca rdiac cycle. Velocity reduction along the ductus was mainly due to its conicity and this reduction generally caused velocity values at the o utlet to be below the normal range. Conversely, angle-independent indi ces measured both at the isthmus and at the outlet lay within the same range of the reported reference values and therefore were not influen ced by sampling site.