Flow-volume relations in coronary circulation and distribution of coronary flow into nutritional and non-nutritional...

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.