BLOOD SUPPLY TO THE HEART 



1527 



tor. Since staining techniques have been notably poor 

 in differentiating vagal and sympathetic terminals, 

 most of the available functional neural anatomy stems 

 from physiologic and pharmacologic observations 



(12, 76). 



Lymphatic Drainage of the Heart 



The myocardial lymphatics arise at the periphery of 

 the capillaries and drain into deep and superficial lym- 

 phatic plexuses. They lie, respectively, immediately 

 subjacent to the endocardium and epicardium, the 

 former draining toward the surface to join in the 

 formation of lymphatic trunks. The vessels course in 

 the anterior and posterior longitudinal sulci and con- 

 dense to form left and right common trunks. The left 

 trunk passes between the pulmonary artery and left 

 atrium, and the right behind the pulmonary artery, 

 both terminating in the "cardiac Kmph node." This 

 node is well delineated in the dog and is regularly 

 found between the innominate artery and superior 

 vena cava (86, 287 I. 



Recent studies have indicated a pathologic simi- 

 larity between experimentally induced myocardial 

 fibrosis secondary to chronic obstruction of the com- 

 mon lymph trunks and idiopathic endocardial 

 fibroelastosis or endomyocardial fibrosis (261). 



PREPARATIONS AND METHODOLOGIES OF SPECIAL 

 INTEREST IN THE STUDY OF THE HEART 

 AND ITS CORONARY CIRCULATION 



Many of the various preparations, procedures, and 

 instruments have been considered in previous reviews 

 (7, 10, 136, 146, 149, 152, 153, 299, 384, 400). 



Preparations 



The coronary circulation has been studied with the 

 heart in various degrees of deviation from the normal 

 state. These preparations include the heart-lung, the 

 isolated heart, and the open or closed-chest animal or 

 human with anesthesia. The use of the nonworking 

 isolated perfused heart by Langendorff in 1895 (221) 

 and by Porter (293), in which arterial inflow and 

 venous outflow could be measured, laid the ground- 

 work for our understanding of the coronary circula- 

 tion. An early bottleneck to the study of the coronary 

 circulation in the isolated heart was the lack of an 

 efficient means of oxygenating the blood. The isolation 

 of the heart connected to its lungs (215), and subse- 



quent use of this preparation by many others (10) 

 contributed extensively to our knowledge of the heart 

 and coronary circulation. There are many variations 

 of this procedure but, in general, the heart and lungs 

 are removed in such a way that the cerebral circula- 

 tion and the vagal and sympathetic nerves remain 

 connected to the heart while the venous return, car- 

 diac output, ventricular volume, heart rate, aortic 

 and pulmonary resistances, atrial, ventricular and 

 arterial pressures, and the chemical composition of the 

 blood can be separately altered and controlled and 

 even cardiac biopsies made. Early in its use, Morawitz 

 & Zahn (272) developed a cannula for insertion into 

 the coronary sinus via the right atrium. The flow 

 through it was presumed to quantitate total venous 

 return from the vessels of the heart. Although this 

 idea was later shown not to be true, the investigation 

 was important for it enabled the experimenter to 

 study the coronary sinus fraction of coronary venous 

 outflow not only in the isolated heart but also in the 

 heart beating in situ. An artificial lung was substituted 

 by Evans et al. in 1934 (107), and since then the de- 

 velopment of such devices and preparations has been 

 rapid, permitting total coronary venous flow measure- 

 ment and fractionation of coronary sinus drainage and 

 noncoronary sinus drainage in the working and non- 

 working isolated heart. Some of the better arrange- 

 ments are as follows: a) Coronary venous drainage is 

 pumped through an oxygenator into the coronary 

 arteries, b) The heart is isolated in a manner similar 

 to the classical heart-lung preparation except that 

 instead of returning the blood to the right atrium and 

 through the lungs to the left atrium, the left ventricle 

 usually discharges its blood through a resistance into a 

 reservoir from which it returns to the left atrium. This 

 is a closed system except for the escape of blood 

 through the coronary vessels into the right heart which 

 receives no other blood (335). This coronary venous 

 blood may be ejected through the pulmonary artery 

 and collected, or it can be separated into coronary 

 sinus and non-coronary sinus fractions by coronary 

 sinus cannulation. In either case the blood goes into 

 the venous system of a donor dog whose arterial system 

 is connected to the reservoir, c) The isolated beating 

 heart doing no external work but with its nerves and 

 cerebral circulation intact may be studied within the 

 chest of dog (or man) by directing systemic venous 

 return through a pump oxygenator into the aorta, thus 

 bypassing the heart. Total coronary venous drainage 

 can be measured in the pulmonary artery or it can be 

 fractionated by also collecting separately coronary 

 sinus flow. The effect of systolic and diastolic ventricu- 



