Coronary arteries are the largest vasa vasorum, as the heart is formed by fusion of two endothelial tubes. The right coronary artery arises from the ostium of the anterior aortic sinus or the right coronary sinus and the left coronary artery arises from the ostium of the left posterior aortic sinus or the left coronary sinus of the ascending aorta. Sometimes the right conus artery, which is usually the first branch of right coronary artery, may arise from the anterior aortic sinus directly. Such an artery is called as third coronary artery. The rise in the coronary heart disease in India has led to a rapid transition in health status. There is a twofold rise and six fold rise of the coronary heart disease in people older than 20 years in rural and urban population, respectively from a period of 1960 to 2010. “Anomaly” refers to the variation that occurs in less than 1% of the general population. Knowledge of normal anatomy of coronary arteries, its variations and anomalies related to coronary circulation is mandatory for good clinical outcome following therapeutic procedures, like angioplasty, coronary artery bypass grafting etc. The present study is conducted to observe the origin, branching pattern, termination and variations of the coronary arteries in human cadaveric hearts. Preponderance of right coronary dominance or left coronary dominance is also looked for in this study.

MATERIALS AND METHODS

For the present study, 70 human hearts were collected from the embalmed cadavers of both the sexes, from the department of Anatomy of our institution. They were preserved in 10% formalin. The specimens were serially numbered from 1 to 70. Visceral pericardium is removed to observe the coronary arteries. The right and left coronary arteries were dissected to observe the origin, branching pattern and variations of the arteries.

OBSERVATIONS

In the present study, in all the 70 specimens, the right and left coronary arteries arose from the anterior and left posterior coronary sinus of the ascending aorta respectively. In 12% of specimens, the left posterior aortic sinus was above the Sino-tubular junction.

Variations Observed in the Right Coronary Arteries: In 2% of specimen, the right conal artery arose from the anterior aortic sinus directly, which is the third coronary artery. In 4% of the specimen, the right coronary artery terminated at the obtuse margin of the heart and in 16% of the specimens, the right coronary artery terminated in between the acute margin of the heart and the crux. In 84% of the specimen, the posterior interventricular septum is supplied by the right coronary artery thereby the diaphragmatic surface of the heart is supplied by the right coronary artery. Hence, in the present study, 84% of the hearts are right dominant.

Variations of the Left Coronary Arteries: In 4% of the specimens, the trunk of the left coronary artery was short measuring less than 5 mm and in 6% of the specimens, the trunk of the left coronary artery measured more than 15 mm. The mean length of the main trunk of the left coronary artery is 9.34 mm, and the length ranged from 2 mm to 17 mm. Trifurcation and quadfurcation of the trunk of the left coronary artery was observed in 26% and 4% of the specimens, respectively. In these specimens, the left coronary trunk branched into left anterior descending artery, which continued as anterior interventricular artery, one or two median arteries and circumflex artery. In 4% of the specimen, the circumflex artery terminated at the obtuse margin of the heart and in 16% of specimens, the circumflex artery terminated by supplying the posterior interventricular septum as the posterior interventricular artery. In the present study, in 70% of specimens, posterior recurrent interventricular artery is present, which is the continuation of the anterior interventricular artery winding around the apex of heart. Myocardial bridges are present in 14% of specimens.

DISCUSSION

For a successful coronary angiogram, knowledge about location, level and size of the ostium is mandatory. A high left coronary orifice is associated with long left coronary artery and thereby iatrogenic injury to the artery during surgical procedures like valvular replacement is possible. High left orifice with low right orifice is the second frequent position of coronary orifice observed in 30% of specimens. In the present study in 12% of cases, left coronary orifice is above the Sino-tubular junction. Coronary dominance is based on the arterial supply to the diaphragmatic surface of heart by either right or left coronary artery. In former studies, 48% of right dominance, 18% of left dominance and 34% of balanced pattern were observed. In the present study, 84% of right dominance and 16% of left dominance is observed. Balanced type is not observed. The right conal artery, at times arises from the right coronary ostium directly and it is called as third coronary artery.

The prevalence of the third coronary artery varies between 33% and 51%. In the present study, third coronary artery is present in 2% of the specimens. There have been considerable variations in the termination of right coronary artery by various authors. The common trunk of left coronary artery is considered to be short, when it is less than 5 mm. The short trunk of left coronary artery has a clinical significance when perioperative coronary perfusion is performed and also during coronary angiogram. Its frequency varies between 7% and 12%. When the length of the left coronary artery is more than 15mm, it is called as long common trunk of left coronary artery. Its frequency varies between 11.5% and 18%. In the present study, 4% of short trunk and 6% of long trunk of left coronary artery is observed. The average length of the main trunk of the left coronary artery in the present study is 9.34 mm and it is near consistent with a study by Reig and Petit with an average of 10.8 mm. Bifurcation of the left coronary artery is commonest branching pattern observed in the present study, which is consistent with other studies. Trifurcation and quadfurcation of the left coronary artery are also observed in this study. However, Penta furcation and single branch of left coronary artery is not observed in the present study, as it is observed in other studies. The median artery could be an important collateral vessel in certain cases. In the present study, the posterior recurrent interventricular artery, which is the continuation of anterior interventricular artery, a branch of left coronary artery, winding around the apex of the heart for up to 2 to 5 cm is present in 70% of the specimens, as compared to 80% in a study by Kalpana R. In majority of the specimens, the left circumflex artery terminates between the obtuse margin and crux of heart. In the present study 80% of the circumflex artery ends in similar fashion and the results are consistent with other studies.Themain coronary arteries usually follow an epicardial route, occasionally the arteries penetrate deeper for a while into the myocardium and again follows epicardial route later on. That part of deeper artery is covered by myocardial fibres, which are named as myocardial bridges. Myocardial bridges are more frequently present along the anterior interventricular artery. Contraction of these myocardial bridges may at times lead to ischemic manifestations, even though heart gets its arterial supply during diastole of heart. In the present study, in 14% of the specimens, myocardial bridges are observed along the course of anterior interventricular artery

Knowledge of coronary arteries anatomy and its variations are mandatory for a successful clinical outcome following treatment of coronary artery diseases. Knowledge about the variations of coronary arteries is helpful for cardiologists and radiologists in performing various procedures like coronary angiogram, coronary angioplasty, and bypass grafting surgeries etc. Therefore, this study is accomplished to contribute to the subject of coronary arteries anatomy and their variations and it is compared with previous studies, thereby emphasizing the need for proper anatomy for a good clinical outcome.

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