The Arteries of the Free Ventricular Walls in Man THOMAS N. JAMES Section on Cardiovascular Research, Henry Ford Hospital, Detroit 2, Michigan The gross anatomy of the arteries of the atria and of the interventricular septum have been described in previous reports (James and Burch, '58a, '58b). This report is a description of the coronary arteries of the right and left ventricles exclusive of the septum, that is, the so-called "free" walls of the two ventricles. A knowledge of anatomy of the coronary arteries of the free ventricular walls is important in understanding coronary disease and its relationship to acute myocardial infarction. The method has been published previously (James and Burch, '58a, '58b; Stern, Ranzenhofer, and Liebow, '54). Briefly, it consists of injection of colored vinyliteacetone solution into the coronary arteries, which have been separately cannulated. The chambers of one side of the heart were then filled with a thicker solution, the right side usually being employed for two reasons: (A) When unfilled it collapsed out of shape whereas the left ventricle did not. (B) The veins could be filled in the same injection directly from the chambers. Casting both sides of the heart made examination of the septa1 arteries difficult. After the plastic hardened, the myocardium was corroded away with concentrated hydrochloric acid. Eighty-two fresh (unfixed) h u m a n hearts were studied and they form the basis of this report. There were 62 males and 20 females. other). There was a second right coronary ostium in about half the hearts (Schlesinger, Zoll and Wessler, '49). Because of its size (usually about 1 mm in diameter) no attempt was made routinely to cannulate and inject it. In most hearts the two coronaries followed the familiar course in the atrioventricular and interventricular sulci. Their principal variations were not in these initial courses but in the eventual length of the vessels, their manner of termination, and the areas supplied on the free ventricular walls. The point of termination of the left circumflex coronary artery was at the margo obtusus or between the margo obtusus and the crux of the heart in 67 (82% ) of the hearts (table 1 and fig. 1). In only 13 hearts ( 1 6 % ) did the left circumflex coronary artery reach or pass the crux of the heart. The right coronary artery reached or passed the crux from the opposite direction in 76 hearts (94% ) (table 2). The left anterior descending coronary artery, which always reached the apex of TABLE 1 Point o f termination o f the l ef t circumflex coronary artery i n 82 human hearts Before margo obtusus At margo obtusus Between margo obtusus and crux At crux Between crux and margo acutus Not present l(l%) 14 (17% ) 53 (65% ) 7(9%) 6(7%) l(l%) RESULTS The aortic origins of the two main coronary arteries only rarely varied from the classical descriptions (Alexander and Griffith, '56). In this series there was only one variation, a heart in which the left circumflex and left anterior descending coronary arteries arose separately from the aorta (their ostia were within 2 mm of each TABLE 2 Point o f termination o f the right coronary artery i n 82 human hearts At margo acutus Between margo acutus and crux At crux Between crux and margo obtusus At margo obtusus l(l%) 5(6%) 7(9%) 53 (65% ) 16 (19% ) 371 372 THOMAS N. JAMES TABLE 3 Point o f termination o f the l e f t anterior descending coronary artery i n 82 human hearts Anterior apex Posterior apex More than two but less than 5 cm up posterior interventricular sulcus More than 5 cm up posterior interventricular sulcus 13 ( 1 6 % ) 20 (24%) 31 (38%) 18 (22% ) TABLE 4 Point of termination o f the posterior descending coronary artery i n 82 human hearts Provided by the left circumflex coronary artery: Half way down posterior interventricular sulcus Three-quarters way down posterior interventricular sulcus At the apex Provided by the right coronary artery: One quarter way down posterior interventricular sulcus Half way down posterior interventricular sulcus Three-quarters way down posterior interventricular sulcus Apex 4(5%) 1 ( 1% ) l(l%) the heart, continued for a variable distance (table 3). It terminated on the anterior or posterior aspect of the apex in 33 hearts (40%), and ascended 2 cm or more up the posterior interventricular sulcus in the remaining 49 (GO% ). The posterior descending coronary artery (table 4) usually arose from the right coronary artery (93% ) but in G hearts (7% ) was provided by the left circumflex artery. Most of the free wall of the left ventricle was supplied by branches of the left coronary artery (table 5). The anterior half of the left ventricular wall (table 6) was almost completely supplied by the left coronary artery in all the hearts. The posterior half of the left ventricle (table 7) was supplied by both right and left coronary arteries, but predominantly by the left (including branches of both the left circumflex and terminal left anterior descending). 2(2%) 23 (28%) 30 (37% ) 21 (26% ) TABLE 7 Blood supply o f the posterior left ventricle ( f r o m middle o f margo obtusus to posterior interventricular sulcus) i n 82 human hearts By coronary artery Left Right TABLE 5 % % Blood supply of the free wall o f the left ventricle ( f r o m anterior interventricular sulcus to posterior interventricular sulcus) i n 82 human hearts 100 0 10 20 30 40 50 60 70 80 90 100 By coronary artery Left Right lo % 0 100 90 80 70 60 50 No. hearts 12 (15%) 19 (23% ) 25 (30% ) 14 (17% ) 7 (9% ) 5(6%) 10 20 30 40 50 TABLE 6 Blood supply o f the anterior left ventricle ( f r o m anterior interventricular sulcus to middle of margo obtusus) i n 82 human hearts By coronary artery Left Right % % 0 100 90 80 10 20 No. hearts 78 (95% ) 3 (4%) l(l%) 90 80 70 60 50 40 30 20 10 0 No. hearts ~ _ _ _ _ _ 11 (13%) 9 (11%) 10iizslo i 11 ii30,'o j 16 (20%) 3 (4%) 9 (11%) 4 (5%) 2(2%) 3 (4%) 4 (5%) ~ _ TABLE 8 Blood supply of the free wall of the right ventricle ( f r o m anterior interventricular sitlcus to posterior interventricular sulcus) i n 82 human hearts By coronary artery Right Left % % 0 100 90 80 70 60 50 40 10 20 30 40 50 60 No. hearts _______ 4 (5%) 30 (37%; 28 (349; j 14 (17%;) 3 (4%1 2 (2% ) 1(l%) _ _ _ ~ FREE WALL ARTERIES TABLE 9 373 their length with a terminal curve downward (fig. 3). Those of the left circumflex artery also arose at an acute angle with the parent trunk and were directed From coronary artery toward the margo obtusus, almost parallel No. hearts Right Left to the primary branches of the left anterior descending coronary artery; near % % 100 0 7 (9%) their termination they usually also coursed 15 (18% ) 90 10 toward the apex of the heart. 80 20 31 (38% ) The primary branches of the right cor70 30 14 (17% ) 60 40 12 (14%) onary artery originated almost at right 50 50 3 (4% ) angles from the parent trunk, thence coursed roughly parallel to each other and TABLE 10 to the margo acutus in the direction of Blood supply of the posterior right ventricle (from the anterior interventricular sulcus, near posterior interventricular sulcus to margo which they anastomosed with s m a 11 acutus) in 82 human hearts branches of the left anterior descending artery. Posteriorly the primary branches From coronary artery No. hearts of the right coronary artery usually arose Right Left perpendicularly from both the atrioven% % tricular sulcus and the interventricular sul100 0 22 (27% ) cus. The primary branches of the anterior 90 10 32 (39% ) 80 20 16 (19% ) right coronary artery, unlike those of the 70 30 3 (4%) left, followed an anteriorly looping course 60 40 3 (4% ) in their origin, due to the relatively deeper 50 50 3 (4%) placement of the parent trunk in the fat 40 60 l(l%) 30 70 1(1%) of the atrioventricular sulcus (fig. 4). 20 80 1(1%) Major variations of the main coronary artery trunks are not common (Alexander The free wall of the right ventricle and Griffth, '56). In this study the proxi(table 8) was supplied principally by the mal right coronary immediately divided right coronary artery. Although the an- into two equal gradually diverging trunks terior half of the right ventricle often re- in 7 hearts. In two other hearts the right ceived blood supply from the left anterior coronary artery distributed in an unusual descending coronary artery (table 9), the manner, one in which a large branch posterior half was almost exclusively s u p curved behind the aorta and emerged in plied by the right coronary artery (table the anterior left atrioventricular sulcus to 10). A small portion of the posterior aspect of the right ventricle near the apex TABLE 11 was frequently supplied by a branch from Blood supply of the posterior wall (from margo obtusus to margo acutus and from atriothe anterior descending artery after it ventricular sulcus to apex) in 82 curved around the apex (figs. 2 and 5). human hearts The blood supply of the entire posterior By coronary artery wall (diaphragmatic surface) of the heart No. hearts was obtained slightly more from the right Right Left coronary artery (table 11). This area was % % the most variable of the heart in relation 100 0 4 (5%) to its blood supply (fig. 2). 90 10 5 (6%) 80 20 9 (11% ) Despite variations in number and size, 70 30 10 (12%) the primary (large) branches of the three 60 40 25 (30% ) main coronary trunks originated in certain 50 50 17 (21% ) general patterns. Those of the left anteri40 60 5 (6% ) 30 70 3 (4%) or descending coronary artery arose at an 20 80 3 (4%) acute angle with the parent trunk and 10 90 l(l%) descended toward the apex for most of Blood supply of the anterim right ventricle (from margo acutus to anterior interventricular sulcus) in 82 human hearts 3 74 THOMAS N. JAMES form the left circumflex artery (there was no such branch from the left main artery), and the other heart in which a similar large branch passed behind the aorta but then descended into the interventricular septum and emerged in the middle of the anterior interventricular sulcus. In one heart the major branches of the posterior descending artery crossed over each other in different planes (fig. 5). Variations in the left coronary arterial trunk were also minor and even less common. The left anterior descending coronary artery was replaced by two parallel and equal trunks in 4 hearts (fig. 6). Although the major trunks were visible in the epicardium in almost all hearts, in one the left anterior descending artery dipped perpendicularly into the myocardium and emerged equally perpendicularly further down (fig. 7). Differential branching of the terminal coronary arteries of the left and right ventricle has long been recognized (Whitten, '30). Over the left ventricle the epicardial branches (of either left or right coronary artery origin) terminate by penetrating the myocardium perpendicular to their epicardial course (fig. 5). Over the thinner right ventricle the epicardial branches (of left or right origin) terminate in a plane parallel to their epicardial course. Anastomoses between the left and right coronary arteries were demonstrated in most of the 82 hearts despite the viscid injection fluid used (fig. 8). Had less viscid fluid been used more anastomoses might have been noted. Because of the relatively small number of females in this study sexual differences in topography of the free wall arteries have to be interpreted without the finality which statistical significance affords. From table 12 certain general observations may be made. When only the extremes of posterior wall preponderance by one coronary artery or the other are considered (group A ) , right coronary artery predominance seems more common in the females; conversely, the left coronary artery was not predominant to this extreme on the posterior wall in any of the females. In males, although right coronary artery predominance was usual, left coronary artery predominance was present in 11% . When analysis was TABLE 12 Distribution of right and left coronary arteries on the posterior wall o f the )heart, according to sex, in 82 human hearts Per cent distribution by nght coronary art. Per cent of 62 males Group A 0- 20 21- 79 80-100 11, 68 21 Group B 0- 30 31- 69 70-100 16 50 34 Group C 0- 40 41- 59 60-100 21 29 50 Per cent distribution by right coronary art. Per cent of 20 females Group A 0 55 45 0- 20 21- 79 80-100 Group B 0- 30 31- 69 70-100 5 45 50 Group C - 0- 40 41- 59 60-100 20 20 60 ~~ based on lesser degrees of preponderance (as in group C) there was virtually no sexual difference. DISCUSSION Previous studies (Gross, '21; Ehrich, De la Chapelle, and Cohn, '31-'32; Schlesinger, '40a, '4Qb; Bianchi, '04; Spalteholz, '24), as well as this one, have agreed in the essential aspects of human coronary artery anatomy. There have been some minor differences, especially in respect to the posterior (diaphragmatic) surface of the heart, which are most likely due to the difference in technics employed for the studies. When the principal or only goal is examination of gross anatomy of the coronary arteries, the most accurate technic is probably the injection and corrosion method. By additionally casting the cardiac chambers an exact spatially oriented replica of the vascular tree of the heart is obtained. 3 75 FREE WALL ARTERIES The variability of the manner in which the posterior surface of the heart is supplied is perhaps not generally appreciated. Significant areas are supplied by the right coronary artery, the left circumflex and left anterior descending, in that order. As has been pointed out (Schlesinger, '40a, '40b; Bianchi, '04) there is in general a reciprocal relationship between the left circumflex and right coronary lengths, and between the left anterior descending and posterior descending arteries at their junction in the posterior interventricular sulcus. Near the central point of this variable area lies the crux of the heart, and the artery crossing this point supplies the blood for the atrioventricular node (James and Burch, '58a, '58b). Classification of blood supply topographically as well by lengths or terminations of major arteries increases descriptive accuracy, for the two classifications provide data which is often considerably different. For example, although a given heart may have a long left circumflex artery lying in the atrioventricular sulcus, its branches may be short and virtually all the posterior free walls be supplied by the right coronary artery and terminal left anterior descending. These descriptions of coronary artery distribution refer to surface area only and can be misleading when one considers the volume of muscle supplied by the respective arteries. For example, in a heart in which the right coronary artery supplies the entire posterior wall as far as the margo obtusus and apex cordis (as "preponderant" as the right coronary artery normally ever becomes), the left coronary artery still supplies all the anterior wall of the left ventricle, a variable part of the anterior wall of the right ventricle, and usually at least two-thirds o € the septum (James and Burch, '58b). In this sense the left coronary artery is almost always preponderant in relation to volume or mass of muscle supplied, and sometimes overwhelmingly so. By considering the variability of the normal coronary arteries one gains a better understanding of the possible electrocardiographic and clinical syndromes expressed by the occlusion of a given coronary artery. For example, occlusion of the left anterior descending coronary artery a few centimeters below the bifurcation of the left coronary artery may damage a widely variable area, depending on the length of the artery (and of course on the availability of collateral circulation). If the left anterior descending artery terminated at the anterior aspect of the apex cordis, the jeopardized area would only be anterior and septa1 and relatively small; while if the artery curved around the apex and ascended over half way up the posterior interventricular sulcus, its occlusion could produce an infarction of both the anterior and posterior free walls and a large part of the septum (Roesler and Dressler, '47). Similarly occlusion of the left circumflex artery near its origin may infarct only a small area of lateral left ventricular wall, or may infarct all the lateral wall plus the posterior wall, depending on whether the area supplied by the artery terminated at the margo obtusus or passed beyond the crux of the heart. The same considerations can be made regarding the right coronary artery, depending on its length. With both these arteries (the left circumflex and right) an occlusion may be associated with atrioventricular block depending on whether they cross the crux and supply the artery to the atrioventricular node. Sexual variation in coronary artery distribution has been noted before by Schlesinger ('40a, '40b), who suggested that the commoner left coronary artery preponderance in males may at least partially account for the sexual difference observed in the clinical frequency of coronary artery disease in the two sexes. The present study supports Schlesinger's observation, and further demonstrates that unless the extremes of preponderance are examined (group A, table 12) the sexual difference in coronary distribution is not so apparent (groups B and C ) . SUMMARY 1. The blood supply to the free walls of the right and left ventricles has been analyzed in a series of 82 human hearts prepared by the injection and corrosion method. 2. The anterior half of the left ventricle was supplied almost exclusively by 376 THOMAS N. JAMES the left coronary artery, but all other areas demonstrated considerable variation both in origin and pattern of supply. This was particularly true of the posterior half of the left ventricle. ACKNOWLEDGMENT Most of this study was done in the Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana. The constant encouragement of Dr. George E. Burch, chairman of the department, i s gratefully acknowledged. LITERATURE CITED Alexander, R. W., and G. C. GrifFith 1956 Anomalies of the coronary arteries and their clinical significance. Circulation, 14: 800-805. Bianchi, A. 1904 Morfologia delle arteriae coronariae cordis. Arch. Ital. Anat. Embriol., 3: 87-164. Ehrich, W., C. De la Chapelle and A. E. Cohn 1931-32 Anatomical ontogeny. B. Man. I. A study of the coronary arteries. Am. J. Anat., 49-50: 241-282. Gross, L. 1921 The Blood Supply to the Heart. New York, Paul B. Hoeber. James, T. N., and G. E. Burch 1958a The atrial coronary arteries in man. Circulation, 17: 90-98. 1958b Blood supply of the human interventricular septum. Ibid., 17: 391.396. Roesler, H., and W. Dressler 1947 An electrocardiographic pattern of infarction of the interventricular septum, extending from the anterior to the posterior aspect of the heart. Am. Heart J., 34: 817-826. Schlesinger, M. J. 1940a Significant variations in the anatomic pattern of the coronary vessels. Blood, Heart and Circulation. A.A.A.S. Publication No. 13: p. 61-72. Ed. F. R. Moulton. Science Press, Washington, D. C. 1940b Relation of anatomic pattern to pathologic conditions of the coronary arteries. Arch. Path., 30: 403415. Schlesinger, M. J., P. M. Zoll and S. Wessler 1949 The conus artery; a third coronary artery. Am. Heart J., 38: 823-836. Spalteholz, W. 1924 Die Arterien der Herzwand. Hirzel, Leipzig. Stern, H.,E. R. Ranzenhofer and A. A. Liebow 1954 Preparation of vinylite casts of the coronary vessels and cardiac chambers. Lab. Invest., 3: 337-347. Whitten, M. B. 1930 The relation of the distribution and structure of the coronary arteries to myocardial infarction. Arch. Int. Med., 45: 383400. FREE WALL ARTERIES Thomas N. James; 1 PLATE 1 Cast of a normal human heart viewed directly at the marqo obtusus (white arrows), showing the left circumflex coronary artery (L. C.) termination there. L. A. D., left anterior descending coronary artery; M. P. A., main pulmonary artery; R. A,, right atrium; G . C. V., great cardiac vein; P. I. V., posterior interventriculsr vein. The left atrium and ventricle are intentionally not cast, as usual. 377 PLATE 2 EXPLANATION O F FIGURES 2 378 Four casts of normal human hearts viewed from the posterior (diaphragmatic) surface, showing the variation in distribution of the right and left coronary arteries i~nthis area. In each photograph the smaller arrows indicate the boundaries between the areas supplied by the left and right coronary arteries. A, B and C show the usual preponderance in this area by the right coronary artery; D shows the exception, i n which t.he left coronary artery is preponderant. The large black arrow in each photograph indicates the crux of the heart. R. A., right atrium; C. S . , coronary sinus; R. C. A., right coronary artery; S . I. V., sub-intimal vein of the right atrium; R. V., right ventricle; L. M. A,, left marginal coronary artery; R. M. V., right marginal vein; and P. I. V., posterior interventricular vein. FREE WALL ARTERIES Thomas N. James PLATE 2 379 PLATE 3 EXPLANATION OF FIGURES 380 3 Cast of a normal human heart viewed from a point between the anterior interventricular sulcus and the margo obtusus, showing the manner of branching of the left circumflex (L. C.) and left anterior descending (L. A. D.) coronary arteries (see text). M. P. A., main pulmonary artery; R. A., right atrium; G . C. V., great cardiac vein; L. M. A,, left marginal coronary artery. 4 Cast of a normal human heart viewed directly a t the anterior right atrium ( R . A.) and right ventricle ( R . V . ) , showing the manner of branching of the normal right coronary artery (R. C. A . ) . S. I. V., sub-intimal vein of the right atrium; M. P. A , , main pulmonary artery. 5 Posterior (diaphragmatic surface) view of a normal human heart cast showing two posterior descending branches of the right coronary artery (R. C. A.) cicossing over each other. Note the apex of the right ventricle (R. V.) supplied by a terminal branch of the left anterior descending coronary artery. The arrows indicate the boundary between regions supplied by the left and right coronary arteries. Differential branching of the arteries over the right ventricle, where they remain straight and parallel to the surface, and the left ventricle, where they turn in perpendicularly, is well shown. C S., coronary sinus; R. A . , right atrium; S. I. V., sub-intimal vein of the right atrium. FREE WALL ARTERIES Thomas N. James PLATE 3 381 PLATE 4 Cast of a normal human heart viewed directly at the anterior interventricular sulcus, where there is a variation of the left anterior descending coronary artery (white arrows) with the upper two-thirds being two parallel trunks, diverging i n the terminal third near the apex. The two black arrows indicate a vein and very small artery forming Vieussens’ ring (see text). R. A , , right atrium; S. V. C., superior vena cava; M. P. A.. main pulmonary zrtery; R. V., right ventricle; G. C. V., great cardiac vein. Cast of a normal human heart with the anterior interventricular sulcus viewed at a n angle from the anterior surface of the lower right ventricle ( R . V. j , showing a dip in the left anterior descending coronary artery betmeen the white arrows; it leaves its normal epicardial course to penetrate deeply but emerges again further down. 6 7 EXPLANATION OF FIGURES FREE WALL ARTERIES Thomas N. James PLATE 4 FREE WALL ARTERIES PLATE 5 Thomas N. James 8 384 Cast of a normal human heart viewed posteriorly, showing normal arterial anastomoses i n the region of the crux. The three smaller arrows in the left lower portion of the photograph indicate an artery approximately 300 micra in diameter connecting a terminal branch of the left marginal coronary artery ( L . A t . A , ) with terminal branches of the right coronary artery ( R . C. A , ) . Variation i n color of the 4 terminal branches of the right coronary artery shown between the two larger upper arrows shows that flow between plastic i n the left coronary artery, which was red, and the right coronary artery, which was blue, has mingled. R. A., right atrium; C. S . , coronary sinus; R. V., right ventricle.