Balance between myogenic, flow-dependent, and metabolic flow control in coronary arterial tree: a model study.

Myogenic response, flow-dependent dilation, and direct metabolic control are important mechanisms controlling coronary flow. A model was developed to study how these control mechanisms interact at different locations in the arteriolar tree and to evaluate their contribution to autoregulatory and metabolic flow control. The model consists of 10 resistance compartments in series, each representing parallel vessel units, with their diameters determined by tone depending on either flow and pressure [flow-dependent tone reduction factor (TRF(flow)) x Tone(myo)] or directly on metabolic factors (Tone(meta)). The pressure-Tone(myo) and flow-TRF(flow) relations depend on the vessel size obtained from interpolation of data on isolated vessels. Flow-dependent dilation diminishes autoregulatory properties compared with pressure-flow lines obtained from vessels solely influenced by Tone(myo). By applying Tone(meta) to the four distal compartments, the autoregulatory properties are restored and tone is equally distributed over the compartments. Also, metabolic control and blockage of nitric oxide are simulated. We conclude that a balance is required between the flow-dependent properties upstream and the constrictive metabolic properties downstream. Myogenic response contributes significantly to flow regulation.