Heart India

ORIGINAL ARTICLE
Year
: 2013  |  Volume : 1  |  Issue : 2  |  Page : 46--51

Variant anatomy of coronary arteries


Jyoti P Kulkarni 
 Department of Anatomy, Dr. D.Y. Patil Medical College, Pimpri, Pune, Maharashtra, India

Correspondence Address:
Jyoti P Kulkarni
Flat No. 6, Oriental Heritage, Manik Colony, Tanaji Nagar, Chinchwad, Pune - 411 033, Maharashtra
India

Abstract

Introduction: Wide variations exist in the size, position, and shape of various body organs, finger prints, and proteins in different individuals. Some variations are of considerable clinical importance, such as the coronary arteries. Variations of coronary arteries can cause important clinical manifestation, including sudden death of the individual. Materials and Methods: Coronary arteries were dissected in 10% formalin-fixed cadaveric hearts. The normal and variant anatomy of coronary arteries was studied. Result: In 100% of cases, the right coronary artery (RCA) and main left coronary artery (LCA) were found to arise from anterior aortic sinus and left posterior aortic sinus, respectively. In 8% of cases, the conus was found to have independent origin from the anterior aortic sinus. The RCA was found to be dominant in 90% of cases. In 66.7% of cases, the length of RCA ranged from 4.5 cm to 7 cm. The average length of LCA was found to be 7 mm. In 10% of cases, the circumflex coronary artery was found to be dominant, where the length of the artery ranged 9-11 cm. In 10% of cases, LCA trifurcated, where the obtuse marginal branch was replaced by the ramus intermedius branch. Also, 43.3% of LAD showed myocardial bridging predominantly in the middle 1/3 rd segment, and 6.7% of cases of RCA showed myocardial looping. Discussion: Coronary arteries show immense variation in their origin, termination, branching pattern, myocardial bridging, looping, and dominance pattern. This knowledge is clinically and surgically important to manage coronary artery diseases.



How to cite this article:
Kulkarni JP. Variant anatomy of coronary arteries.Heart India 2013;1:46-51


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Kulkarni JP. Variant anatomy of coronary arteries. Heart India [serial online] 2013 [cited 2021 Mar 5 ];1:46-51
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Full Text

 Introduction



Coronary arteries are the greatly enlarged vasa vasora, which supply blood to the heart in the form of ring and sling. The right and the left coronary arteries arise from the aortic sinus of valsalva at the root of the aorta and encircle the base of ventricles like a crown. Variations of coronary arteries can be fatal. It can lead to sudden death during strenuous activity. A cadaveric study in unsuspected population can help understand the variations that will be useful to determine the prevalence of certain variations.

 Materials And Methods



A detailed dissection of coronary arteries in 60 cadaver hearts fixed in 10% formalin was carried out in the Department of Anatomy. The coronary arteries and their branches were dissected in the atrioventricular and interventricular grooves on the surface of heart. Origin, branching pattern, dominance, length, myocardial bridging, and looping of the arteries was studied. The length of the arteries was measured with the help of thread and millimeter scale.

 Results



In all 60 cases, the dissected right coronary artery (RCA) was found to arise from the anterior aortic sinus [Table 1]a. In 65% of cases, where the range of length of RCA was around 8-14 cm, the artery was dominant, i.e., the posterior descending (PD) branch and branch to AV node was found to be a branch of RCA [Figure 1] [Table 3]. The branch to SA node in all the cases was found to be a branch from RCA [Figure 2] [Table 1]b. The conus was found to arise from RCA in 92% of cases [Figure 2] and [Figure 3]. However, in 8% of cases, the conus had an independent origin from the anterior aortic sinus [Figure 4] [Table 1]a. The acute marginal branch arose from the RCA at the right border of heart. The range of length of this branch was found to be 3-4.5 cm in 23%, 4.5-7 cm in 66.7%, and 7-10 cm in 10% of cases [Table 3]. PD artery and artery to AVN was found to be a branch of RCA in 90% and branch of circumflex in 10% of cases. In 60% of cases, the length of PD artery was found to be in the range of 5-7.5 cm [Table 4]. In all 60 cases, the dissected left coronary artery (LCA) was found to originate from the left posterior aortic sinus of the ascending aorta. The average length of LCA was found to be 7 mm, after which, it bifurcated or trifurcated [Tables 1] a, 1b, [Table 2] In 16.6% of cases, the LCA trifurcated into left anterior descending (LAD), circumflex (CX), and ramus intermedius (RI) branch [Figure 5], while, in 83.3% of cases, it bifurcated into LAD and CX branch. In all 60 cases, the LAD and CX were found to be the branches of LCA. The length of CX was found to be 3-5 cm in 20%, 5-9 cm in 70%, and 9-11 cm in 10% of all cases. In these, 10% of cases with the maximum length of the circumflex coronary artery was found to be dominant, i.e., the PD and branch to AVN were found to be the branches of CX coronary artery. The length of LAD was seen to be 4-7 cm in 3%, 7-10 cm in 16.6%, 11-14 cm in 66.6%, and 14-17 cm in 13.33% of all cases. In the range of length from 10 cm to 17 cm, the LAD was found to turn around the apex of the heart and anastomose with PD branch. Along its length, the LAD gave rise to 2-3 diagonal branches on its left side. The obtuse marginal artery was found to be a branch of circumflex coronary artery in all 60 cases. However, in 10 cases where the LCA trifurcated, the OM was replaced by the RI branch of LCA [Figure 5] [Table 2].{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Figure 5}{Table 1}{Table 2}{Table 3}{Table 4}

In 6.7% of cases, the RCA showed myocardial looping [Figures 1] and [Figure 2] and, in another 6.7% of cases, the PD showed myocardial bridging [Table 5]. The myocardial bridging was seen in LAD in 43.3% of cases [Figure 6], while circumflex showed myocardial looping in 16.7% of cases [Figure 7]. The myocardial bridging was seen predominantly in the middle 1/3 rd segment of the LAD in 26.7% of cases [Figure 6] [Table 6].{Figure 1}{Figure 2}{Figure 6}{Figure 7}{Table 5}{Table 6}

 Discussion



The RCA, after arising from the anterior aortic sinus, usually gives the following branches: Branch to SA node, conus, acute marginal, PD, and branch to AV node. PD branch gives septal branches to the posterior 1/3 rd of interventricular septum. The LCA usually bifurcates into LAD and circumflex coronary artery. The LAD gives septal branches to the anterior 2/3 rd of interventricular septum. It also gives 2-3 diagonal branches on the sternocostal surface. The circumflex coronary artery gives obtuse marginal branch and ends at the crux of the heart by giving PD branch and branch to AV node. The PD and branch to AV node decides the dominance of coronary arteries. If it is a branch of the right coronary, it is called as right-dominant circulation. If it is a branch of CX, then it is said to be left-dominant circulation. Codominance may also exist. Usually, the coronaries lie on the myocardial surface. Occasionally, the myocardium may cover a segment of branches of coronary arteries; these are called as myocardial bridges. When the coronary arteries run in an atriventricular groove, the atrial musculature may loop around the arteries; these are called as myocardial loops. However, the coronary arteries showed a considerable variation in the branching pattern, length, and myocardial bridging. According to Loukas et al., (2009), [1] it is desirable to determine the incidence of variations that are potentially capable of producing sudden cardiac death. In the present study, the prevalence of independent origin of the right conus from the anterior aortic sinus was 8%, wherein it showed the presence of an accessory ostium in the anterior aortic sinus. This ostium was relatively smaller in size and was situated higher to that for the RCA. In 1967, Baroldi and Scomazzoni [2] described the prevalence of independent origin of right conus to be about 36%. Similar findings were noted by Bhimalli et al.,. [3] Since the accessory ostium is very small, it may fail to get opacified during angiographic procedures. In all 60 cases, the RCA arose from the anterior aortic sinus. However, RCA may have ectopic origin from the LPAS. The prevalence of this ectopic origin was observed to be 0.0008% on angiographic studies, as mentioned by Yarnanaka and Hobbs [4] and 0.043-0.46%, as studied by Solanki et al. [5] Simkoff (1982) [6] reported a case of anomalous origin of RCA from the LAD. Multiple attempts to cannulate this artery were unsuccessful and an aortic flush injection confirmed its absence.

In the present study, the branch to SA node was seen to arise from the RCA in all 60 cases. However, in 1978, Hutchison [2] described a variable origin of the branch to SA node from circumflex coronary artery in 35% of cases, which is a significant fact. In 1961, James [2] described the course of main LCA, wherein he stated that the branch to SA node may arise from the LCA. Kini et al., [7] found that the branch to SA node arose as the branch of RCA in 55% of cases on computed tomography (CT) angiograms.

In the present study, in 90% of the cases, the RCA was dominant, i.e., the branch to AV node and PD branch is a branch of RCA in 90% of the cases. A dominant right coronary terminates beyond the crux by giving 2-3 posterior lateral ventricular branches. In 60% of the hearts, the RCA reaches the crux and terminates a little to the left of crux in a variable degree of anastomosis with the circumflex branch of the LCA. In 10% of the cases, it ends near the right cardiac margin or between this and the crux and, in 20% of the cases, it may even reach the left border of the heart, replacing the terminal part of circumflex. The range of length was 8-14 cm in 65% of cases, where the artery was dominant.

The LCA, which usually arises from LPAS, terminates by bifurcation into LAD and circumflex coronary artery. However, in the present study, it trifurcates in 16% of the cases, thus giving rise to RI branch that runs along the obtuse margin of the heart. However, the prevalence of occurrence of RI is 35-50%. [2] The incidence of ectopic origin of the circumflex from the right sinus of valsalva is reported to be 1.6-1.2%. [8] In a study by Demetrios, it was found to be 0.64%. [8] Calvalcanti (1995) observed that, in 1.82% of the cases, the CX and LAD arose directly from the ascending aorta. [9] In the present study, the length of LCA was found to be 5 mm in 76.7% of cases, while it was found to be 10 mm in 5% of cases. Waller et al., [10] found the length of LCA to be 6 mm in 76% of all cases and 10 mm in 3% of all cases. Davies et al., quoted the length of LCA to be <6 mm in 36% of all cases and >20 mm in 5% of all cases on cine angio films. In early bifurcation of LCA, the coronary cannula may selectively perfuse one main branch and occlude the others. [11] Short length of LCA may be a predisposing factor to coronary artery disease. [12]

In the present study, the circumflex coronary artery dominated in 10% of the cases. The origin of PD and the branch to AV node decided the dominance pattern. Mian et al., found circumflex to be dominant in 19.5% of the cases, while they found co-dominance in 20% of the cases. [13] Reddy found the circumflex to be dominant in 11.26% of all cases and codominance in 2.5% of all cases. [14]

In the present study, the branch to SA node arose as a branch from RCA in 100% of cases. However, it may arise from circumflex, usually from its anterior part traversing the interatrial septum to supply the SA node, thus establishing a direct or indirect anastomosis with the RCA, as mentioned by Kugel in 1927. [15] The appearance of the left conus was not a constant feature; it was seen in 3 out of 60 cases, originating either from LCA or LAD.

Variation in the origin of coronary arteries and their branching pattern can pose difficulties in imaging by conventional catheters, thereby creating problems in diagnostic and therapeutic interventions.

In the present study, the overall prevalence of myocardial bridging and looping was found to be 88% on cadaver dissection. It was found to be more common in the left coronary system (60%) than in the right coronary system (23.8%). In the left coronary system, the myocardial bridging was frequently seen in the LAD artery (43%). In the LAD artery, it was more commonly found in the middle 1/3 rd portion of the artery. A variation was encountered by the occurrence of myocardial bridging over the proximal and distal segments. This finding concurs with the findings reported by Sabnis. [16] Along its course in the right atrioventricular groove in 6.7% of the cases, RCA showed myocardial looping, which is an anatomic variation.

The frequency of myocardial bridging in left anterior interventricular was 23% according to Geringer [17] and 85.7% according to Polaeck, [18] based on cadaveric dissection. The myocardial bridges over the branches of RCA are rare as they are found in 2.8 to 11.4% of cases. Muscular loops occur more frequently in the course of circumflex as compared to that in RCA. There is a paucity of references regarding myocardial loops in the literature. The overall incidence of myocardial bridging in LCA was found to be 77.1%, while it was found to be 41.4% in RCA in a study by Poelack. [18] Kramer [19] in 1982 stated that myocardial bridges that are present right from the period of development are not the source of myocardial ischemia. The frequency of detection of bridging in angiographic films is 0.5-12%. [20] It is seen as a systolic narrowing of arteries in a coronary angiogram. The findings of myocardial bridging in the present study concurs with that of Bandopadyay [21] et al., and Vanildo, [22] who found it to be 90.40% and 86.6%, respectively. However, it was 65.7% in a study by Sabnis [16] and 55.60% in a study by Ferreira. [23] These values are less as compared to that found in the present study. Myocardial bridge may cause myocardial ischemia. It may require surgical repair and supra arterial decompression myotomy. Localization and progression of stenotic lesions of coronary arteries can be influenced by anatomical characters of coronary arteries. [24] Study of myocardial bridges requires further in-depth analyses.

 Conclusion



Most of the variations are totally benign; some are errors of embryological developmental timing or persistence of an embryologic condition. Coronary artery variations are important from clinical and surgical point of view. The study of coronary artery variation is important to prevent false interpretation of the coronary artery angiograms and to study and manage diseases related to coronary arteries.

 Acknowledgement



Department of Anatomy, Seth GS Medical College, KEM Hospital, Mumbai.

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