Flow‐volume relations in coronary circulation and distribution of coronary flow into nutritional and non‐nutritional compartments

Abstract

Simultaneous assessment of coronary flow and flow-volume relation makes it possible to evaluate the dilatatory responses of coronary vasculature. A new set up of methods for investigation of the coronary circulation was employed to study the nature of the coronary flow and volume responses to dipyridamole in dogs. The turnover rate of coronary blood, the reciprocal value of the mean transit time, can be accurately determined by computer simulation analysis of coronary dye dilution curves. After intravenous dipyridamole (0.5 mg/kg) both coronary turnover rate and electromagnetically assessed blood flow were observed to increase in parallel and to the same degree (+55%). This indicates that no increase in the coronary vascular volume and, accordingly, no significant overall coronary dilatation takes place. The effective coronary blood flow in relation to the myocardial oxygen consumption, i.e. the nutritional flow, and the myocardial oxygen consumption decreased by 25% concomitant to a corresponding fall in myocardial oxygen requirements. Thus, the increase in total coronary flow after dipyridamole is useless for myocardial metabolism, and may properly be denoted as luxury perfusion or throughput flow.

MRI quantitative myocardial perfusion with compartmental analysis: A rest and stress study

“…Moreover, because vessels are included in the myocardium compartment, one can argue that dipyridamole increases both myocardial blood flow and vascular volume by vasodilatation, and that the increased K, is related more to a volume increase than a flow effect. By comparing the mean transit-time of coronary blood with the coronary blood flow, Virtanen et al (23) deduced that no significant increase in the myocardium blood volume is induced by dipyridamole. With adenosine (a final effector of dipyridaniole), Cristal et al (24) found no change of the blood volume of small vessels with a diameter <loo pm, but did find a 35% increase of the total coronary blood volume (including the main coronary arteries).…”