Key result
An electrical analog model demonstrated that the nonlinear pressure-flow relationships of coronary collaterals depend heavily on the experimental setup and collateral distensibility.
This electrical analog model demonstrates that experimental setup significantly influences the observed nonlinear pressure-flow relationships of coronary collaterals, with back-pressure setups underestimating total collateral flow.
Model findings urge caution in collateral flow estimates; leaves open validation in human physiology.
The pressure-flow relationship of the coronary collaterals is investigated by using an electrical analog model that combines the coronary epicardial arteries with the nonlinear characteristics of the intramyocardial circulation. The study aims to examine some controversial issues concerning the collateral circulation, including the transmural distribution of the collaterals, the distensibility of the collateral vessels (whether rigid or complaint), the effects of microcirculatory embolization, the collateral zero-flow pressure, and the nonlinearity of the collateral pressure-flow relationship. The study is carried out by simulating and comparing two basic experimental set-ups in which a coronary artery is ligated and the retrograde flow serves as an index of collateral flow. In the first "free-flow" setup, flow is allowed to bleed retrogradely against atmospheric pressure while perfusion pressure to the rest of the coronary arteries is varied over a wide range. In the second "back-pressure" setup, the coronary perfusion pressure is maintained at the control levels while the back pressure to the retrograde flow in the excised artery is varied. According to the analysis, the nonlinear pressure-flow relationships depend heavily on the experimental setup and are a function of the distensibility of the collaterals, which are distributed mainly on the epicardial surface, and the nonlinear contraction characteristics of the myocardium. The measured retrograde flow tends to underestimate the total collateral flow for the back-pressure setup because of antegrade flow escape.
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Manor et al. (1994) studied Coronary collateral circulation. Electrical analog model of coronary collaterals was evaluated on Pressure-flow relationship of coronary collaterals. An electrical analog model demonstrated that the nonlinear pressure-flow relationships of coronary collaterals depend heavily on the experimental setup and collateral distensibility.
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