RELATIONSHIP BETWEEN STRUCTURAL AND HEMODYNAMIC HETEROGENEITY IN MICROVASCULAR NETWORKS

The relationship between structural and hemodynamic heterogeneity of m icrovascular networks is examined by analyzing the effects of topologi cal and geometric irregularities on network. hemodynamics. Microscopic observations of a network in the rat mesentery provided data on lengt h, diameter, and interconnection of all 913 segments. Two idealized ne twork structures were derived from the observed network. In one, the t opological structure was made symmetric; in another a further idealiza tion was made by assigning equal lengths and diameters to all segments with topologically equivalent positions in the network. Blood flow th rough these three networks was simulated with a mathematical model bas ed on experimental information on blood theology. Overall network cond uctance and pressure distribution within the network were found to dep end strongly on topological heterogeneity and less on geometric hetero geneity. In contrast, mean capillary hematocrit was sensitive to geome tric heterogeneity but not to topological heterogeneity. Geometric and topological heterogeneity contributed equally to the dispersion of ar teriovenous transit time. Hemodynamic characteristics of heterogeneous microvascular networks can only be adequately described if both topol ogical and geometric variability in network structure are taken into a ccount.