THE MAGNITUDE, ADEQUACY AND SOURCE OF THE COLLATERAL BLOOD FLOW AND PRESSURE IN CHRONICALLY OCCLUDED CORONARY ARTERIES

Abstract

The results presented elucidate in part what happens dynamically in the vascular bed of a chronically occluded coronary artery in dogs under favorable conditions, and have led to the belief that a large new collateral circulation develops. The recorded exptl. facts show that in 22 of 23 dogs the peripheral coronary pressure is greatly increased (as compared to normal controls) and at times to values even approaching aortic pressures; the retrograde blood coming from the peripheral end of the occluded coronary ranges up to 105 cc. per min. with most of the values around 30 to 40 cc. per min.; the retrograde blood is so similar to arterial blood that it cannot be differentiated on the basis of its CO2 and O2 content; and such vol. flows of arterial blood are sufficient for the metabolic needs of the potentially infarcted myocardium, for the myocardial region exhibits normal contractions except in areas of scarring. No single pulse pattern or set of ordinate values exists in the peripheral ends of the chronically ligated major coronary rami. The most usual peripheral coronary pressure is similar in timing and contour (although greater in magnitude) to the normal curve obtained immediately after coronary ligation; others more nearly resemble an intraventricular pressure curve while less frequently the peripheral coronary pressure curve can scarcely be distinguished from the simultaneously recorded aortic curve. Most of the collateral flow occurs during diastole and only in those coronary pressure curves which resemble the aortic in ordinate values and contour can the source of the retrograde blood be predicted. By clamping the other coronary arteries either separately or together while measuring the retrograde flow in the 3d chronically occluded coronary, the functional extent of the newly established coronary anastomoses has been detd. The descendens receives on an avg. 62 to 66% of its collateral flow from the other coronaries (right 7% and circumflex 55%). The circumflex receives 66 to 64% from the other coronaries of which the right and descendens contribute 19 and 47%. The right receives 97 to 79% of its flow from the left coronary artery, the descendens contributing 22% and the circumflex 75%. This leaves a large residual flow in the left coronary and a small residual flow in the right still to be accounted for. The origin of this potential extracoronary retrograde flow has not been detd.