|Year : 2014 | Volume
| Issue : 3 | Page : 143-149
Angiographic profile of coronary arteries in Keralite population
Associate Professor of Anatomy, Government Medical College, Kozhikode, Kerala, India
|Date of Web Publication||21-Jan-2020|
M P Apsara
Associate Professor of Anatomy, Government Medical College, Kozhikode - 673008, Kerala
Source of Support: None, Conflict of Interest: None
Background and aims: The incidence of Coronary Artery Disease (CAD) has reached alarming proportions in India. The pathological hall mark of CAD is myocardial ischemia resulting from the atherosclerotic narrowing of coronary arteries. In this era of advanced interventions and cardiac surgery, a thorough knowledge of normal and variant anatomy of coronary arteries is of prime significance and of great use both to the clinicians and anatomists. Materials and methods: One hundred coronary angiograms of patients free of disease were studied in detail in different profiles. The data obtained was quantified according to their frequencies. The relation between the length of left main coronary artery and coronary artery dominance was statistically analyzed using the ‘Chi Square test for Trend’. Results: This study highlighted some interesting findings such as the origin of Sino- atrial nodal artery from the second segment of right coronary artery in 3% of cases, double right marginal artery in 4% cases. Other variations such as Mouchet’s posterior recurrent interventricular artery, origin of circumflex artery from the right coronary artery and abnormal communication between the terminal parts of right coronary artery and circumflex artery were each noticed in 1 % of cases. Conclusions: Coronary arteries and their branches are prone to variations in their course and morphology. Prior knowledge about this is important for the interpretation of coronary angiograms and surgical myocardial revascularization. The present work on normal and variant pattern of coronary arteries will help in gathering momentum to the already advancing research work in this field.
Keywords: Coronary Artery Disease (CAD), Coronary angiogram, Left Coronary Artery (LCA), Left Anterior Descending artery (LAD), Circumflex artery (Cx), Right Coronary Artery (RCA), Posterior Descending artery (PDA)
|How to cite this article:|
Apsara M P. Angiographic profile of coronary arteries in Keralite population. Natl J Clin Anat 2014;3:143-9
| Introduction|| |
Coronary arterial distribution has been the matter of subject for extensive investigations. The two coronary arteries- Right Coronary Artery (RCA) and Left Coronary Artery (LCA) which supply the heart encircle the base of ventricles like an oblique inverted crown. Analysis of resin corrosion casts and the results of radio opaque perfusion studies have revealed intra and inter coronary anastomoses in vessels up to 100-200 micro meters in caliber. But clinical experience suggests that the anastomoses can not rapidly provide collateral routes sufficient to circumvent sudden coronary obstruction and thus the coronary circulation is assumed to be end arterial.
The minimal requirements for the normality of coronary arteries include the following criteria:
- The dual aortic origin from right and left coronary ostia.
- The course of RCA follows the right atrioventricular grove.
- The course of LCA follows the left atrioventricular groove and anterior interventricular groove.
- The Posterior Descending Artery (PDA) originatesfrom either the RCA or Circumflex artery (Cx).
- The major coronary arterial branches traverse epicardially.
- The coronary arteries terminate at the myocardial capillary level.
The term ‘variation’ is a non specific term referring to an entity that is different from normal where as ‘anomaly’ is any congenital deviation that is seen in less than 1% of otherwise normal individuals. A detailed knowledge of normal and variant anatomy of coronary arteries is of prime importance in the management of coronary artery disease. Worldwide epidemiological studies show that the frequency of deaths from Coronary artery disease (CAD) is increasing with each decade of life. Today, with the widespread use of diagnostic imaging techniques, it has become easy to study the normal and variant patterns of coronary arteries. The present coronary angiographic study is an attempt to understand the normal and variant patterns of coronary arteries in the Keralite population.
| Materials and Methods|| |
The present study was conducted under the guidance of interventional Cardiologist in the Cardiac catheterization laboratory of Government Medical College Hospital, Thiruvananthapuram over a period of three years. After getting ethical committee clearance, one hundred coronary angiograms which showed normal anatomy, variations and anomalies were included in the study group whereas angiograms with abnormalities like diffuse atherosclerosis, aneurysms and occlusions were excluded. Each coronary artery was studied in detail, giving emphasis to the principal branches and their variations.
RCA was studied in left anterior oblique-LAO; left anterior oblique cranial-LAO cranial; right anterior oblique-RAO views of right coronary angiograms. LCA was studied in left anterior oblique caudal-LAO caudal; left anterior oblique cranial-LAO cranial; anteroposteior caudal-AP caudal; anteroposteior cranial-AP cranial, right anterior oblique cranial-RAO cranial; right anterior oblique caudal-RAO caudal views of left coronary angiograms. The length of main trunk of left coronary artery was measured in millimeters using the Quantitative Coronary Angiography (QCA) software. Single frame obtained at end diastole was used for this. The orifice of left coronary artery was visualized by the spillback of contrast medium. The association between the length of left main trunk and coronary artery dominance was studied. This data was analyzed using Chi Square test for Trend (x for Trend) and the statistical significance was expressed as ‘p value’.
| Results|| |
Right Coronary Artery (RCA)
RCA originated from right sinus of Valsalva in all cases.
The conus branch of RCA was identified in 74% of cases. It is presumed that in the remaining cases, it could have a separate origin from right coronary sinus- the third coronary artery.
SA nodal artery
SA nodal artery originated from RCA in 68% of cases, where as it originated from circumflex branch of LCA in 32% of cases. Origin of SA nodal artery from the second segment of RCA was detected in 2 cases [Figure 1].
|Figure 1: LAO cranial view of RCA showing the origin of S A nodal artery from the second segment of RCA (white arrows)|
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Right marginal artery / acute marginal artery
The right marginal artery originated from RCA as a single vessel in 96% of cases. Duplication of right marginal artery was present in 4% of cases [Figure 2].
|Figure 2: LAO cranial view of RCA showing the double right marginal artery (white arrows)|
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Posterior Descending Artery (PDA)
In 79% of cases PDA originated from RCA - the RCA dominance. 15% of cases showed LCA dominance in which PDA originated from the circumflex branch of the LCA. In 6% of cases the PDA took origin from both RCA and circumflex branch of LCA - Co-dominance.
AV nodal artery
The origin of AV nodal artery from the inverted U loop of terminal part of RCA was clearly visualized in many cases.
Left Coronary Artery (LCA)
LCA originated from left sinus of Valsalva in all cases. The length of main trunk of this artery varied between 1-25 mm. Short left main trunk (<6mm) was detected in 18% cases. In 67% cases, it was of medium length (615 mm), where as 15% of cases showed long left main trunk (>15mm).The relation between the length of left main trunk and coronary artery dominance was analyzed using Chi Square test for Trend [Table 1]. The association between short left main coronary artery and left coronary artery dominance was found to be statistically significant (p value < 0.001). Bifurcation and trifurcation of left main trunk were reported in 80% and 19% respectively.
|Table 1: Length of left main coronary artery and coronary artery dominance|
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Left Anterior Descending artery (LAD)
Significant variation in the level of termination of LAD was noted. Termination of LAD beyond cardiac apex was detected in 77 % of cases. The LAD terminated before cardiac apex in 4% of cases and at cardiac apex in 19% of cases. In one angiogram, LAD was so long to replace the PDA - Mouchet’s posterior recurrent interventricular artery [Figure 3].
|Figure 3: RAO cranial view of LCA showing Mouchet's posterior recurrent interventricular artery (white arrow)|
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Circumflex artery (Cx)
The circumflex artery originated from RCA in one patient [Figure 4] where as another angiogram showed abnormal communication between terminal parts of circumflex artery and RCA [Figure 5].
|Figure 4: LAO cranial view of RCA showing origin of Circumflex artery from RCA (white arrow)|
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|Figure 5: LAO cranial view of RCA showing inter-coronary communication (white arrow)|
Abbreviations: LAO-Left anterior oblique; RAO - right an - terior oblique; RCA - right coronary artery; a-1 st segment of RCA; b - second segment of RCA; SNA-SA nodel artery; RMA - right marginal artery; PDA - posterior descending artery; LCA - left coronary artery; LAD - left anterior de - scending artery; Cx - circumflex artery.
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| Discussion|| |
The coronary arterial distribution is one of the most sought after anatomical domains in the background of exponential rise of coronary artery disease. The RCA originates from the right sinus of Valsalva and it descends in the right atrioventricular groove. The course of the artery is divided into two segments. First segment extends from its origin to the right margin of the heart and the second segment extends from the right border to the crux of the heart.
The conus artery finds itself in a strategic position between the RCA and the LAD and is a potential path of anastomosis to either of these major vessels. By definition, the origin of conus artery separately from the right aortic sinus is termed the third coronary artery. The incidence of third coronary artery was reported by Schlesinger et al in 55% of cases whereas Olabu et al reported its incidence in 35% of cases. Whatever be its origin, the conus branch has a relatively constant distribution over the infundibulum.
The most common site of origin of SA nodal artery is from the first two centimeters of RCA. Habbab et al noted the angiographic finding of S shaped SA nodal artery from the distal part of dominant RCA in a patient with atrial septal defect. Sewell studied the human coronary arteries using selective cine coronary arteriography and suggested that SA nodal artery was occasionally quite prominent and might rarely be a source of collateral channel to the circumflex artery through its left atrial branch. The variable origin of SA nodal artery from different portions of RCA and Cx branch was documented by Hutchinson and Nerantzis et al showed its importance in the blood supply of atrial myocardium. Duplication of right marginal artery was present in 4% of cases. According to Sewell there is usually one and sometimes two moderate sized or large right marginal arteries arising from the second or third quarter distance between the origin of RCA and acute margin of heart. The acute marginal branch is relatively large and constant, and is directed towards apex. Jochem et al explained the importance of anastomoses of the right marginal artery with conus artery and LAD in patients with CAD.
The Posterior Descending artery (PDA) irrespective of its origin from the RCA or the LCX is the chief source of blood supply to the posterior diaphragmatic portion of the interventricular septum. Levin and Baltaxe reported the incidence of double PDA in 6% of cases. According to them, when there is a dual supply of the posterior interventricular septum, multiple stenoses might necessitate construction of two different bypasses to provide adequate revascularization. Level of termination of PDA in relation with posterior interventricular septum was documented by Kalpana. The origin of PDA whether from RCA or Cx is the main factor determining the coronary artery dominance. The comparative figures in this study with respect to literature are given in [Table 2],,.
Much like the S A nodal artery, AV nodal artery is an important source of blood to the inter-atrial septum. AV nodal artery whether from right or left coronary arteries, always arises in the region of the crux of the heart. It is a small artery which passes straight upwards and identifies the crux.
The left main coronary artery may be classified into short (<6mm), medium (6-15mm) and long (>15 mm),. Pioneering work done by Gazetopoulas et al showed the inverse relation between the length of left main coronary artery and incidence of atherosclerosis in its branches. Present study showed a statistically significant association between the short left main trunk and left dominant pattern of coronary circulation which was previously reported by Kronzon et al.
Documentation of the length of left main trunk has its greatest practical application in patients undergoing aortic valve replacement with selective coronary perfusion. Awareness of length of left main vessel is helpful in preventing selective perfusion of either the circumflex artery or LAD in patients with short left main vessel.
Fox et al also reported the higher incidence of short left main trunk and its risk in aortic valve surgery. Selective hyperperfusion of one vessel usually the LAD with concomitant underperfusion of the second vessel may cause severe myocardial derangements including posterolateral wall myocardial infarction and subendocardial hemorrhage. The risk will be even higher if the underperfused vessel is the dominant Cx artery. The diagonal artery which is usually a branch of LAD may arise from the junction of LAD and Cx arteries. This trifurcation of left main coronary artery was previously reported by many workers,, [Table 3].
|Table 3: Division of left main coronary artery as reported in the literature|
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Paulin documented the levels of termination of LAD in relation with cardiac apex. Comparative figures of present study are given in [Table 4]. Spindola-Franco et al in a coronary angiogram study reported Dual-LAD which was defined as early bifurcation of the LAD into two vessels: a short LAD which remains in the anterior interventricular sulcus and does not reach the apex and a long LAD which leaves the anterior interventricular sulcus only to return to the distal sulcus and continues to the apex. The portion of LAD that is lodged in the posterior interventricular groove is known as Mouchet’s posterior recurrent interventricular artery and it may extend to the crux replacing the PDA’,. In this case, circulation of interventricular septum depends entirely on LAD. A hyper-dominant LAD which replaced PDA coexisting with aortic stenosis was reported by Javangula and Kaul.
Anomalous origin of Circumflex artery from the RCA was noted in one patient without any other cardiac abnormality. Its initial course was retro-aortic, but peripheral distribution was normal. This was previously documented by many authors,. LCA continued as LAD and had a normal distribution. Abnormal communication between the terminal parts of RCA and Cx artery was noted in one patient. Such a communication was a major source of blood supply as the entire left coronary system was visualized by injection of dye into RCA. Inter-coronary communication is a rare anomaly usually occurring in the absence of CAD and it may be mistaken for a functioning collateral vessel indicative of an unrecognized coronary obstruction. This anomaly is totally benign. According to James the connections between terminal branches of coronary arteries requires no special description but when they function for major blood flow, they usually enlarge to lmm or more in diameter and become tortuous and elongated, an appearance which is in contrast to their shape in normal hearts. Origin of Cx from RCA and inter-coronary communication belong to Class 1- Benign Clinical relevance- based classification of coronary artery anomalies (CAA) by Rigatelli and Rigatelli.
| Conclusion|| |
Present work highlights the fact that the coronary arteries and their branches are subject to many variations. The enormous number of interventional coronary care units in different parts of our country is a pointer to the fact that more and more patients are being admitted due to coronary artery disease. India especially Kerala has caught up with the western world when it comes to the prevalence of coronary artery disease. Present work on normal and variant patterns of coronary arteries can be taken as a yard stick and will be of immense help to the clinicians in diagnosing atherosclerotic narrowing of these arteries and planning surgical myocardial revascularization.
The author acknowledges Dr.K.Chandrakumari, Dr.K. Sivaprasad and Dr.S.D. Nalinakumari for their valuable suggestions and able guidance.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4]