Oxygen Sources and Sinks in Myocardial Hypertrophy

Abstract

The capillary supply of the heart is traditionally characterized by the mean capillary density, i.e. the number of capillaries per unit area of tissue cross-section. It is possible to estimate the average inter-capillary distance using the data on capillary density and accepting a certain uniform geometrical arrangement of the capillary network. The average intercapillary distance then yields the radius of the tissue cylinder supplied by a single capillary which can be used in calculation of myocardial PO₂ according to the Krogh-Erlang equation (1). A basic deficiency inherent in such a calculation is that a uniform distribution of capillaries is assumed. However, it has been shown both by measurements in vitro (histology, e.g. (2)) and in vivo (cinemicrophotography, e.g. (3)) that this is not the case. The heterogeneity of capillary spacing, in turn, has a pronounced effect on myocardial oxygenation as demonstrated in a series of our theoretical studies (4, 5). Until recently, there was no method available to evaluate the pattern of distribution of capillaries in histological sections. Recently, several methods for direct or indirect estimates of the heterogeneity of capillary spacing have been proposed (method of concentric circles (6); triangular method (7); closest individual method (8); capillary domains (9)).