THE PHASIC AND MINUTE CORONARY FLOW DURING ACUTE EXPERIMENTAL HYPERTENSION

Abstract

Using anesthetized dogs with open chest and intact vagi, blood pressures were detd. in the aorta, a large ramus of the left coronary artery and a side branch of the left coronary. Records were made of variations in these pressures as well as the maximum systolic coronary resistance. Graphs were made of individual cardiac cycles, the differences between the aortic pressure curves and the peripheral coronary pressure curves being plotted also against a base line and so giving an area graph from which could be measured the amount of coronary flow during different portions of the cardiac cycle. Comparing normal cycles with those made during aortic compression and during administration of epinephrine made it possible to compare coronary flow changes due to increased aortic pressure, increased or decreased heart rate and differing pulse pressures. Because of a greater pressure differential, and longer diastole, the coronary flow per cycle and per minute was greatly increased during hypertension due to compression of the aorta. The coronary flow was also increased during hypertension due to epinephrine, although the flow during systole was decreased due to a marked increase in peripheral coronary pressure. The author concludes that the biggest factors concerned in increasing the blood supply to the myocardium during these experimental hypertensions are the greater head of aortic pressure and a longer relative period of diastole.