Microheterogeneity of myocardial blood flow

Abstract

Myocardial blood flow exhibits the most marked heterogeneity at the microvascular level. Its within-layer spatial distribution can be described from subepi- to subendocardium with resolutions of 0.1 × 0.1 to 1 × 1 mm² by quantitative digital radiography based on the technique of desmethylimipramine deposition. In the subendocardium, flow heterogeneity is the highest, whereas local flow randomness is the lowest, showing the clustered pattern of high- or low-flow regions. The resolution-dependence of flow heterogeneity is characterized by its fractality, which holds consistently down to the microvascular level through the vascular structural transition from the treelike arteriolar to the non-treelike capillary network. Flow heterogeneity is adjustable in a transmurally different manner to local metabolic changes. The redistribution of flow is considered as a result of adaptive coordination of microperfusion between adjacent microcirculatory units, which are perfused by a single precapillary arteriole.