Are Flow Transport Capacities and Metabolic Requirements Matched Regionally in the Myocardium?

Abstract

Data were acquired on the uptake of metabolic substrates and on well-retained ions in small regions of the myocardium, 1 to 2 min after injection into the left atrium, and compared with estimates of local myocardial blood flows in each of the 250 to 500 regions, per heart. The data showed approximately linear relationships between the deposition of these solutes and the local flows. Models for blood-tissue exchange kinetics based on an assumption of the constancy of permeability-surface area products for capillary and cellular uptake in all regions being the same were not compatible with the data. Using axially distributed multiregional models appropriate to the solutes, the data could be fitted only when the permeability-surface area products were proportional to the local flow in each region. Within myocardial pieces of 0.1 to 0.2 G, the range of flows was about six-fold; if within the pieces having the lowest flows the regional metabolism was at the average rate for the whole heart, tissue viability could not be supported by flows available. These regions must therefore have less than average metabolic requirements. Likewise high flow regions would be extravagantly perfused if their metabolic rates were at the average rate. We conclude that although the link between transport capacities and flow is well established, that between local metabolism and flows is not proven, but it is highly likely that local flows transport capacities and metabolic requirements are well matched.KeywordsMyocardial Blood FlowImpedance MatchRegional Myocardial Blood FlowFatty Acid AnalogFlow ProportionalityThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.