HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



and the free right ventricular wall by the right 

 coronary artery. The most variable area is posterior, 

 and it is by virtue of the communication of the poste- 

 rior descending artery with either the left or right 

 coronary artery, or both, that the designation "domi- 

 nant" pattern has arisen (18, 37, 84, 153, 258, 348). 

 Hence, dogs are universally left coronary dominant, 

 the left circumflex branches supplying the posterior 

 left and right ventricles, the posterior septum and 

 A-V node. This pattern is the least common in man 

 and pigs, approximating 20 per cent of cases in the 

 former. Pigs are generally right coronary dominant, 

 while man, both living and autopsied, and the higher 

 primates manifest this pattern half of the time and a 

 balanced circuit in approximately a third (37, 63, 

 84, 153, 348). In the perfused human heart, however, 

 this pattern of dominance is not found (370). 



The secondary divisions of the major coronary 

 branches in man are consistently different over the 

 two ventricles, the branches of the anterior descendens 

 and left circumflex arising at acute angles and cours- 

 ing to the apex, while those of the right coronary 

 arise at right angles and course toward the anterior 

 interventricular sulcus (191). The terminal branches 

 are likewise different; those over the left ventricle are 

 perpendicular to the epicardial course, while those 

 over the right ventricle are parallel. Once the arteries 

 penetrate the myocardium, they lose their tortuosity 

 and linearly follow the muscular grain in a plane 

 between the superficial and deep muscle layers (153, 

 191, 258). 



The functional supply to the conducting tissue 

 bears further comment since it has been shown in 

 man and dogs that mortality and morbidity are in- 

 creased when ligation of vessels includes septal and 

 nodal arteries (5, 61, 246). Of the three atrial branches 

 from each coronary artery, the cristal branch of the 

 dorsal right atrial artery is the major supply to the 

 S-A node in man (60-70%) and dogs; rich anastomo- 

 ses exist with the ventral left atrial artery in 75 per 

 cent of dogs whereas, in man, this latter vessel is the 

 major supply to the S-A node in 40 per cent (1 53, 1 72, 

 173, 189, 190, 399). In rats and dogs (172, 174), and 

 possibly in man, anastomoses with extracardiac ves- 

 sels are readily shown at the junction of the superior 

 vena cava and right atrium. Rats have a dual blood 

 supply to the heart, the atrial and S-A nodal vessels 

 stemming from cardiaco-mediastinal branches of the 

 internal mammary and subclavian arteries, while the 

 ventricles, A-V node, and parts of the atria are sup- 

 plied by the coronary arteries. 



Recent vinylite cast techniques have shown a 

 consistent artery to the region of the A-V node arising, 



BRANCH TO 

 AV NODE 



R. CORONARY A 



LEFT ANT DESC. 

 CORONARY A. 



POST 

 DESC. 

 CORONARY 

 A. 



fig. 2. Drawing of the blood supply of the normal human 

 interventricular septum. Note the preponderance of supply by 

 the left anterior descending coronary artery and the U-turn of 

 the posterior right coronary artery which gives off the branch 

 to the atrioventricular node. [From James (189).] 



in man, from that coronary artery which crosses the 

 posterior crux (189-191, 246). Thus, in 80 percent, 

 this was the right coronary, the left in 10 per cent, and 

 from both in another 10 per cent. In 100 per cent of a 

 large series in dogs (246), a similar vessel arose at the 

 crux from the left circumflex coronary. This vessel, 

 variously named the posterior septal artery and ramus 

 septi fibrosi, courses along the base of the interatrial 

 septum and penetrates the annulus fibrosus to supply 

 the His bundle and upper interventricular septum 

 (246, 399) (fig. 2). In its course it freely anastomoses 

 with atrial vessels, predominantly the dorsal left 

 atrial artery and, from below, the anterior septal 

 arteries. 



The interventricular septum receives its blood sup- 

 ply from the anterior septal artery and penetrating 

 branches of the anterior and posterior descending 

 arteries (36, 172, 173, 189, 190, 246, 258). The former 

 is well developed in dogs but in man and higher 

 primates it is somewhat vestigial, although easily 

 identified as the first and largest branch of the anterior 

 descendens. 



The anterior branches in man are 40 to 80 mm in 

 length, supply the anterior two-thirds to three-fourths 

 of the septum, and penetrate near the right ventricular 

 side remaining under the right ventricular endo- 

 cardium before terminating deeper in the septum. 



