The effect of cell size and capillary spacing on myocardial oxygen supply.

Recently, we collected basic morphometric data from normal and hypertrophic rat hearts: median and mean values of the cell diameter and of the intercapillary distance as well as their variabilities. In the present communication we used these data, first for analysis of the effect of the heterogeneity of capillary spacing on the myocardial tissue PO2. Comparison of tissue PO2 histograms calculated for a situation in which the capillaries are evenly distributed as in the Krogh model, with a situation based on the same capillary but variable intercapillary distances clearly demonstrates the importance of heterogeneity of the capillary spacing as a separate oxygen determinant. This is even more important in the hypertrophic hearts which are characterized by longer and more variable intercapillary distances. In the second part, we compared the classical Krogh model with a model of concentric diffusion in which the oxygen consumption was either uniform or divided into two zones of distinctive rates. Oxygen profiles calculated for the Krogh model with excentric diffusion were similar to those derived for the two models of concentric diffusion.