MATHEMATICAL-MODEL OF BLOOD-FLOW IN A CORONARY CAPILLARY

The coronary capillary flow is analyzed theoretically based on continu um mechanics. The capillary is a long, elastic, and permeable vessel l oaded externally by tissue pressure, and it is subject to possible per iodic length changes, together with adjacent myocytes. Capillary flow is driven by arteriolar-venular pressure difference. Ultrafiltration d ue to transmural hydrostatic and osmotic gradients is included, and co nsideration of mass conservation leads to a nonlinear flow equation. T he results show that under physiological conditions ultrafiltration is of minor importance, and the analysis predicts regional differences i n capillary flow. In regions with high tissue pressure (subendocardium ), capillaries undergo significant periodic volume changes, giving ris e to intramyocardial pumping. In those regions, capillary wall elastic ity is of major importance. In regions with low tissue pressure (subep icardium), the possible periodic capillary length changes are predomin ant. The predicted flow patterns are in good qualitative agreement wit h measured epicardial phasic flow. In conclusion, the methodological a dvantage of a distributive analysis is demonstrated by its ability to elucidate and evaluate the role of flow determinants and their complex interactions.