Complexity analysis of placental blood flow in normal and high-risk pregnancies.

Various strategems of complexity analysis of microvascular blood flow were carried out in several fields of medicine in the past, as such as angiology, ophthalmology and neurology. The introduction of colour-angio-mode, a special form of colour coded Doppler sonography, now makes possible to perform complexity analysis of the placental blood displacement even in the absence of information about hydrodynamic details such as directionality, velocity profile and number of displaced blood cells. Algorithms were developed which allows to extract information concerning the time averaged power of phonon-erythrocytes collision events (from the square of the frequencies of back scattered ultrasound recorded during 166 ms) in 20,000 to 40,000 regions of interest. The obtained values are being displayed as false coloured pixels on a video-screen, we succeeded to obtain quantitative data about displacement rates.In cross-sectional and longitudinal studies we generated typical diagrams displaying the "occurrence rate" of various powers of displacement over time. By this mode of display contour plots can be generated, showing a large amount of low intensity pixels and a small amount of high intensity pixels representing the parenchymatous blood flow inside the placenta. As was to be expected, interdependencies between the placental blood flow and the maternal and fetal heart rates as well as the maternal breathing can be found. While there was only limited influence of maternal and fetal heart rate on the placental blood flow, maternal breathing showed striking influence. Surprisingly, during expiration the power of placental blood movement was decreased, and there was a marked increase during inspiration. In cases of severe intrauterine growth retardation, colour pixel intensities were seen to transiently vanish during end-expiration. The power of placental blood displacement was marked increased subsequent to reducing maternal hematocrit during hemodilution therapy by infusion of artificial colloids. These interdependencies could be confirmed by ex vivo examinations perfusing and percolating the placenta after birth in a hemodynamic model. Additionally, we found interdependencies between fetal and maternal blood displacement inside the placenta. By modelling the decrease of fetal inotropic power in the ex vivo examinations, increase in the power of maternal blood displacement in the intervillous space. The two types of placental blood flow are known to be determined by many factors. While it is currently impossible to measure all these parameters determining an parenchymatous blood flow, it is possible to obtain useful informations about the physiologic and pathophysiologic changes of placental blood flow using colour-angio-mode as a tool of complexity analysis based on the distribution of local blood displacement. This new knowledge can help to understand clinically relevant changes in the individual patient as well their underlying causes.

Analysis of the inter- and intravillous placental blood circulation in high-risk pregnancies before and after the hemodilution therapy using the colour-angio-mode.

OBJECTIVE: The aim of the study was to examine the efficiency of a hemodilution (HD) therapy on the inter- and intravillous placental blood circulation in high-risk pregnancies by applying the colour-angio-mode (CAM). PATIENTS AND METHODS: 24 patients were examined who had fetal growth retardation and/or pathological Doppler results. In all cases the hematocrit was >36%. The patients were given 500 ml Ringer solution and 500 ml HAES 10% intravenously per day; maternal heart rate and blood pressure were measured continuously. Prior to and after the therapy the same area of the placenta was examined using CAM; histograms demonstrating the distribution of the intensity values and summation values of the color pixels were calculated. RESULTS: In 14 patients the fetal outcome was good. The histograms showed in 11/14 cases an increase of low intensity values indicating an improvement of the placental circulation. The summation value of the color pixels as measured by CAM was significantly increased after the therapy in these cases (p = 0.022). In 10 patients the fetal outcome was unfavorable. The histograms showed a decrease of the intensity values in 6/10 cases. There was no significant change in the summation values of the color pixels after the therapy (p = 0.139). CONCLUSIONS: CAM sonography demonstrated for the first time a local effect of the HD therapy within the placenta. In the positive case the placental blood circulation will improve and the pregnancy develops favourably (responder). In the negative case there is no change of the placental blood circulation and pregnancy must be terminated due to a pathological fetal heart rate tracing, fetal growth failure or hypertensive disorders (nonresponder).

Antenatal visualization of vascular anastomoses in monochorionic twins using color Doppler sonography: the protective function of these anastomoses and the phenomenon of interference beating.

This report concerns the antenatal visualization and velocimetry of an arterioarterial and a venovenous anastomosis in a monochorionic twin pregnancy using color Doppler sonography. The phenomenon of 'interference beating' occurs when two flow velocity waveforms are superimposed in one blood vessel. This characteristic image can be generated antenatally to confirm the existence of a vascular communication. We were able to reveal these anastomoses postnatally using the dye injection technique.

Fluid drop-like transition of erythrocytes under shear.

Red cells dispersed in a continuous medium of high viscosity possess the flow properties of fluid drops. The cells at rest are biconcave, while under shear they become progressively deformed into prolate ellipsoids, their long axis aligned parallel to the flow direction. The red cell membrane rotates around the hemoglobin like a tread of a tank. At high rates of shear this mechanism greatly reduces viscosity at all hematocrit values.