

HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



occlusion, or as venous channels for the whole myo- 

 cardium in the presence of extensive superficial vein 

 constriction or occlusion. Regarding the first situation, 

 although essentially complete occlusion of the coro- 

 nary arteries in human beings has been found at 

 autopsy (227), the presence or extent of development 

 of extracardiac arterial collaterals is not known. In 

 addition, with temporary functional separation of one 

 or both coronary arteries from the aorta, no blood 

 flow from the ventricles into the superficial coronary 

 venous system can be demonstrated and the hearts do 

 not survive (153). When dye is injected into the right 

 ventricle in acute experiments, extensive capillary 

 injection on the surface of both ventricles occurs if 

 right ventricular pressure is artificially made to exceed 

 left ventricular pressure (153). Although this could 

 have occurred through the Thebesian channels of the 

 interventricular septum (265), the anterior cardiac 

 veins were not excluded as a portal of entry for the 

 dye. Regarding the second situation, with acute 

 closure of all grossly visible anterior cardiac veins or 

 of the coronary sinus, or both, a considerable reduction 

 in right and left coronary inflow occurs (153). Al- 

 though the heart, following acute closure of both the 

 coronary sinus and anterior cardiac veins, becomes 

 exceedingly hemorrhagic and progressively weaker, 

 such hearts may survive up to 2 hours. Dogs in which 

 both superficial venous systems have been chronically 

 occluded in a two-stage operation have survived for 

 periods of months. However, that significant drainage 

 occurs through such a route could not be verified, 

 since, at postmortem examination, these hearts 

 exhibited numerous superficial cardiac veins of con- 

 siderable size which were not previously apparent, and 

 several large extracardiac venous anastomoses, the 

 aggregate cross section of which was estimated to be 

 adequate for venous drainage of the entire heart ( 1 53). 

 Until the intracardiac and extracardiac arterial and 

 venous collaterals which appear with coronary arterial 

 or venous ligation have been excluded as flow chan- 

 nels, any conclusion regarding the utilization of deep 

 coronary venous drainage channels in diseased hearts 

 is difficult to reach. 



Possible Use of Left Coronary Artery Flow Together 

 with the Chemical Composition of Coronary Sinus 

 Blood as an Index of Left Ventricular Metabolism 



It is not possible to quantitate accurately the 

 metabolism of the right ventricle in dog (or man) 

 because its superficial anterior cardiac veins have 

 many exits into the right atrium and their contained 



blood is grossly contaminated by blood from the left 

 coronary artery. However, a large drainage of the 

 left myocardium occurs into the coronary sinus and 

 the latter is accessible. Hence, the question of whether 

 the chemical composition of coronary sinus blood 

 together with left coronary inflow can be used as an 

 index of quantitative changes in metabolism of the 

 left ventricle is a very practical and important con- 

 sideration because of the widespread use by the basic 

 experimenter and the clinical investigator of these 

 measurements for this purpose. To justify such usage, 

 experimental evidence must show, first, that most of 

 left coronary inflow drains into the coronary sinus 

 and that the latter is not significantly contaminated 

 by drainage from the right coronary artery and, 

 second, that its chemical composition approximates 

 that portion of the blood coming from the left coronary 

 artery which does not flow through the coronary 

 sinus. 



In the open-chest dog in which no great effort is 

 made to avoid obstruction at the ostium, the per- 

 centage recovery in the coronary sinus of left coronary 

 inflow varies from 64 to 83 per cent in any one dog, 

 and shows little variation from dog to dog (153)- By 

 use of a special cannula which collects all the blood 

 draining into the coronary sinus without obstruction 

 to any of its veins, the percentage of left coronary 

 artery inflow recovered in the coronary sinus is quite 

 high (80-90 %) and reasonably constant during the 

 induction of a variety of physiological variables and 

 drug injections (300). In the open-chest dog, the 

 right coronary artery contributes not more than 2 to 3 

 per cent, or 1 to 2 ml per min, to the coronary sinus 

 flow, and this only occasionally. This has been deter- 

 mined by observing minimal changes in coronary 

 sinus flow when the right coronary artery is clamped 

 in the presence of an elevated right ventricular pres- 

 sure from pulmonary artery stenosis, when right 

 coronary artery clamping is superimposed on a pre- 

 existing occlusion of the left coronary artery (153), 

 and by observing only minimal changes in the optical 

 density of coronary sinus blood following massive 

 injection of Evans blue dye into the right coronary 

 artery (300). 



The investigation of whether the coronary sinus 

 fraction of blood is representative in chemical compo- 

 sition of total left coronary venous return started with 

 the experiments of Evans & Starling in 1913 (106) and 

 has continued to the present time. Actually, investiga- 

 tions during this period did not directly attack the prob- 

 lem (158). In these experiments, the effect of increased 

 right ventricular pressure was determined on flow 



