Temporospatial heterogeneity of myocardial perfusion and blood volume in the porcine heart wall

Spatial heterogeneity of myocardial perfusion has been recognized for many years. Whether this is primarily the result of heterogeneity of parameters such as myocardial metabolism, of intramyocardial mechanical forces, or of vasomotor function within the myocardial microcirculation, is not clear. A practical problem is that it has been almost impossible to measure any two of these parameters simultaneously in the same piece of myocardium so that an unambiguous correlation, much less a cause-and-effect relationship, has been difficult to establish. In this study of six anesthetized pigs, we propose that whole-body computed tomography is a method for providing the simultaneous measurement of heterogeneity of myocardial perfusion (F) and myocardial blood volume (p). The first finding was that the empirical relationship p=AF+BF^{0 5} between myocardial blood flow (F) and intramyocardial blood volume (p) is maintained over a range of sizes of regions of interest {approximately 1 to 0.125 cm³) within the myocardium of each individual animal despite the spatial heterogeneity of the F and the ñvalues. The value of A ranges from 0.014 to 0.021 min and of £ranges from 0.061 to 0.076 ml^{0 5} g^-0.5 min^0.5. A second finding was that the pattern of spatial heterogeneity of F and of p remained reasonably stable over at least a 1 h period.