BLOOD SUPPLY TO THE HEART 



I5 ! 9 



fig. I. Vinylite cast of a human heart. Anterolateral aspect 

 of left ventricle following digestion of muscle. M.P.A. = main 

 pulmonary artery; R.A. = right atrium; L.A.D. = left anterior 

 descending coronary artery; L.C. = left circumflex coronary 

 artery; G.C.V. — great cardiac vein, P.I.I'. = posterior inter- 

 ventricular vein. [From James (191).] 



In humans it terminates 40 per cent of the time at the 

 apex, and in 60 per cent, ascends 2 cm or more in the 

 posterior longitudinal sulcus, while in rabbits it 

 rarely reaches the apex (64, 84, 153, 191, 258). It is 

 covered by bridges of ventricular myocardium for 

 most of its course (292). There are from two to seven 

 ventricular branches, the large left ventricular 

 branches coursing over the anterior surface toward the 

 apex, the small right ventricular branches crossing the 

 interventricular groove to supply a narrow band of 

 muscle and to anastomose with right coronary 

 branches. Anastomoses exist with anterior ventricular 

 branches of the left circumflex coronary artery and 

 at the apex, with the latter's marginal branch and 

 the posterior descending artery whether of circumflex 

 or right coronary origin (18, 189, 191, 258, 337). 

 Septal branches penetrate deeply from the underside 

 of the vessel all along its course in the anterior sulcus. 



In humans, primates, and pigs, these branches are not 

 supported as in dogs and rabbits by an individual 

 septal artery arising from the main left coronary or 

 origin of the descendens. A fairly constant branch to 

 the pulmonary conus region exists in most species. 



The left circumflex follows the auriculoventricular 

 groove to the left, coursing under the left auricular 

 appendage and terminating at a variable distance 

 from the posterior longitudinal sulcus. It is largely an 

 epicardial vessel, surrounded by areolar and adipose 

 tissue, and rarely covered by muscular loops (292). In 

 dogs it almost always reaches or crosses the crux of the 

 posterior sulcus, terminating as the posterior descend- 

 ing artery, whereas in pigs (64, 289) it rarely does so. 

 In man, higher primates, and rabbits, the vessel 

 usually ends at the obtuse margin (63, 78, 191, 258). 

 An average of three anterior ventricular branches and 

 three atrial branches occurs in man and dogs (36, 

 64), the former coursing to the apex to anastomose 

 with the anterior descendens branches. Posteriorly, 

 communications exist with the right coronary either 

 from the posterior descendens or the marginal 

 branches. In the dog a branch of the left circumflex at 

 the posterior crux passes deep to supply the A-V node 

 and His bundle (172, 173). 



right coronary artery. The main right coronary 

 artery arises from a single ostium in its aortic cusp, 

 but not infrequently, especially in dogs and primates, 

 smaller ostia of accessory branches are also present 

 (63, 258, 290). The right coronary passes anteriorly 

 behind the pulmonary artery and follows the respec- 

 tive auriculoventricular groove to the right (acute) 

 margin of the heart. In dogs and rabbits it usually 

 terminates here as the marginal branch, whereas in 

 pigs and man it invariably (93 %) reaches the posterior 

 crux to become the posterior descending artery (64, 

 191, 289). In its course it gives off an average of three 

 atrial branches, one of which, the dorsal (posterior) 

 right atrial artery, is the major supply to the S-A 

 node in man and dog (172, 190), and three to five 

 right ventricular branches. Posteriorly, in man and 

 pigs, a branch to the A-V node is given off at the 

 crux, corresponding to the branch from the circum- 

 flex in dogs (172, 189, 190, 246, 258, 399). A constant 

 branch to the pulmonary conus frequently arises from 

 an accessory ostium. 



Although it is evident that the course and distribu- 

 tion of the coronary arteries is basically similar in the 

 various species mentioned, the ramifications are such 

 as to permit a breakdown into patterns of dominance. 

 Thus, in all species, the entire anterior and lateral 

 left ventricle is supplied by the left coronary branches, 



