This preclinical study demonstrates that coronary blood flow correlates with perfused myocardial tissue volume independently of vasomotor tone, and that vasodilation increases capillary surface area at a constant perfusion pressure.
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Preclinical finding warrants no change in coronary disease management; leaves open whether capillary recruitment operates similarly in humans.
The amount of tissue perfused, as determined from the difference in volume of distribution between a diffusible indicator (125I-antipyrine) and an intravascular indicator (131 I-albumin) was measured at different values of coronary flow, perfusion pressure, and vasomotor tone in the working left ventricle of an open-chest dog. Coronary pressure and flow were regulated independently from the systemic circulation and coronary vasomotor tone was reduced by dipyridamole. At each flow vasomotor tone was assessed by using as a reference the maximal vasodilation induced by arrest of flow. Measured tissue space was considered to be related to the capillary surface area available for tracer diffusion and therefore to the number of perfused capillaries per volume of muscle. A relationship between coronary blood flow and tissue volume was observed. It was found to be independent of vasomotor tone. Vasodilation was found to increase available exchanging capillary surface at a constant perfusion pressure.
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L’Abbate et al. (1976) studied this question.
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