ANATOMICAL VARIATION IN BRANCHING PATTERN AND DOMINANCE IN CORONARY ARTERIES : A CADAVERIC STUDY

Address for Correspondence: Dr Vandana Ravi, Assistant Professor, Raichur Institute of Medial Sciences, Raichur, Karnataka. E-Mail: drvandanar@gmail.com Background : The human heart is supplied by two right and left coronary arteries which arise from ascending aorta. Left coronary artery is wider in diameter and its branches supplies greater volume of myocardium & larger part of interventricular septum. Right coronary artery supplies right atrium and right ventricle. Detailed appreciation of normal origin,course,branches and myocardial distribution of these vessels is vital so that variation of normal anatomy can be more easily recognized and it is must to identify the course of coronary artery disease and perform therapeutic, radiodiagnostic and surgical procedure. Result: Study was conducted on 30 heart specimens. Coronary arteries (CA) were dissected to know origin, location of ostia in relation to sinotubular junction (STJ) & variation in branching pattern. No variation was found in the origin, but in 10% of specimen’s right coronary ostia was above the STJ and 90% of specimens it was below the STJ and in 93.3% of specimens left coronary ostia was below STJ and in 6.6% it was above STJ. The third coronary artery was found in 26.6% of specimens. Right coronary dominance was observed in 83.3%, Lt dominance in 13.3% and co-dominance in 3.3% of specimens. The mean length of trunk of LCA was found to be 14.5±4.42mm, minimum length we observed was 5mm,which is the shortest length of trunk of LCA reported so far and maximum length observed was 25mm. Bifuracation, trifurcation, tetrafurcation and pentafurcation of LCA was observed in 80%, 13.3%, 3.3%, and 3.3% of the specimen respectively. Conclusion: An intimate knowledge of the coronary arteries the “Crown” of the heart and its variations is prerequisite for cardiac surgeons for proper diagnosis and treatment of cardiac ailments and for radiologists to refine the image interpretation.

ascending aorta from its anterior aortic sinusand left posterior aortic sinuses.The two arteries as indicated by their name form an oblique inverted crown, with anastomotic circle in the atrioventricular sulcus connected by marginal and interventricular loops intersecting at the cardiac apex.They usually run subepicardially but those in the atrioventricular and interventricular sulci are deeply sited, occasionally The coronary system of arteries consisting of two arteries is appeared to be recent evolutionary acquisition, fish and amphibians have only one coronary artery and only 60% avian species have2 coronary arteries [1].The human heart is supplied by two coronary arteries and their branches, which issue from hidden by myocardium.The left coronary artery (LCA) wider in diameter than the right coronary artery (RCA), gives normally left circumflex and left anterior descending artery.LCA supplies greater volume of myocardium larger part interventricular septum and most of the left heart.RCA arises from anterior aortic sinus, it gives a conus, marginal and posterior interventricular branches and supplies right atrium, ventricle.
The term dominant is used to refer the coronary artery which gives posterior interventricular branch supplies the posterior part of interventricular septum and part of posterolateral wall of left ventricle.[2] An intimate knowledge of the coronary arteries the "Crown" of the heart and its variations is prerequisite for cardiac surgeons for proper diagnosis and treatment of cardiac ailments and for radiologists to refine the image interpretation.

MATERIALS AND METHODS
The study was carried out on 30 adult cadaveric heart specimens collected from the department of Anatomy of our Institution.Heart Specimens were obtained from the cadavers dissected for undergraduate students.The specimens were numbered 1 to 30.Dissection method was followed 1. Gross dissection 2. Micro dissection method Gross dissection was done with following instruments Forceps (pointed, blunt and toothed) Scalpel Scissors The coronary arteries were traced through epicardium and subepicardial adipose tissue.
The observations were made with respect to its origin, level of ostium, in relation to sinotubular junction, length of trunk of LCA, normal branching pattern, variations in branching pattern, course,dominance and presence or absence of myocardial bridge.To see the location of ostia the ascending aorta was transversely sectioned approximately 1cm above the commissure aortic leaflets.The aorta was then longitudinally opened at the level of right posterior aortic sinus which enabled us to analyse the level and number of ostia with respect to sinotubular junction [4].After dissection ostia were cleaned and then photographed using digital camera.Micro dissection: Micro dissection was carried out by using hand lens to trace the terminal branches.

RESULTS AND DISCUSSION
It was observed that in all the 30 heart specimens 3 aortic sinuses were present and all the ostia were related to aortic sinuses.The RCA was found to be arising from the anterior aortic sinus and LCA from left posterior aortic sinus and double ostia were found in some of the specimens.ostia were observed in relation to STJ, as shown below.Variation was observed in the origin of posterior interventricular artery (PIVA), in some specimens it was arising from Rt coronary artery as usual, in some specimen it was originating from Lt coronary artery and in some it was arising from both arteries.Normally the LCA bifurcates into left anterior descending artery (LAD) and left circumflex artery (Cx) but variations were also observed in the branches of bifurcation of LCA.(Tabe-4) In all trifurcation LCA was dividing into one LAD, one diagonal and one circumflex branch.In tetrafurcation it was dividing into one LAD, two diagonal and circumflex arteries.In pentafurcation LAD, three diagonal and one circumflex branch.(Fig- 5).Variation in the origin of Circumflex branch was also found, it was arising from LCA in 23 specimens (76.6%) & from diagonal artery in7 specimens (23.3%).Myocardial bridge was observed during the study on posterior interventricular artery (PIVA) in 6 specimens (20%) and left anterior descending artery in 7 specimens (23.3%) respectively.In the present the right coronary ostia was below the sinotubular junction in 90% and above sinotubular junction was 10%.The left coronary ostium was situated below the sinotubular junction is 93.3% and above sinotubular junction was in 6.6% of specimens.Our observations were nearer to the observations reported by KalpanaRA and Bhimalli shilpa.
Generally there is only one orifice in the anterior aortic sinus from which the right coronary artery originates; however more than one orifice is sometimes observed.It has been observed that right conus branch originate from this accessory orifice; in this case, the conus branch is called the 3rd coronary artery.Its frequency of occurrence varies (7.6%-51%) and some ethnic differences have been observed to exist.The present study shows the right dominance in 83% specimen and left dominance is 13.3% of specimens.Which are near to the observations made by Calcavanti et al and KalpanaRA.[12,20] In some specimens we observed more than one PIVA.We also observed co-dominance in 3.3% of specimens which was very less when compared to the studies done by Kurjia The length of the trunk of left coronary artery in general varies from 2 -12mm but it may be upto 30mm.[21 Green G E et al studied the length of left main coronary artery in 50 consecutive autopsy specimen in which 48% of cases, the length of left coronary artery was 10mm or less and in remaining 52% of cases, the length was up to 25mm.The short left main coronary artery explain some failures of adequate coronary perfusion.During aortic valve surgery, myocardial perfusion depends on the placement of one or more cannulas in the coronary arteries.In this regard, the length of left main coronary artery prior to its bifurcation is particularly important [22].P Dharmender reported the mean length of left coronary artery was found to be 9.2± 0.31mm [23].Ballesteros LE et al reported average length of trunk of left coronary artery was 6.48± 2.57mm.Fox et al have reported the shortest length to date 5.5mm [24].
Our study showed the average length of trunk left coronary artery was 14.5±4.42mmshortest length we have observed was 5mm which is even shorter than the shortest length till date reported by the author Fox et al, maximum length observed was 2.5mm in our specimen.Short trunk of left coronary artery could be at risk during aortic valve replacement surgeries.The catheter may be inserted into one of the terminal branches, thereby producing an ischemic area, which can lead to arrhythmia, myocardial ischemia or both.Short trunk also been considered as a risk factor in developing coronary atherosclerosis [24].The termination of left main coronary artery varies from 2 or more branches and accordingly named as bifurcation, trifurcation, tetrafurcation and pentafurcation.Previous studies have reported wide variations in branching of trunk of left coronary artery and have found greater prevalence of bifurcated expression.Table 6 shows report of various authors in termination of trunk of left coronary artery.the study.[42,22,3] In present study also we have observed the presence of myocardial bridges over LAD and PIVA in 25% and 29.16% of specimens respectively.
In the present study we observed higher frequency of bifurcation (80%) compared to the previous reports (
5% and LAD and common trunk or stem in 16.6 of specimens.Such observations of LAD and common stem from trunk of LCA have not been reported so far.During our study we also observed variations in the origin of circumflex branch, in 23.3% of specimens it was arising from diagonal branch.Such variation has not been reported so far in the literature.Rajani singh et al, Ballesteros LE et al (2008), Fazligullari et al (2010), David M Fiss (2007), CONCLUSION Rate of coronary artery related disease in increasing by leaps and bounds in recent times.The anatomy of coronary arteries has recently been re-emphasized in association with the use of coronary arteriography.The high degree of variability of the coronary arteries and their branches must be carefully observed and studied from anatomical, pathophysiological, diagnostic and therapeutic viewpoints.The advances made in coronary artery bypass surgery and newer methods of myocardial revascularisation demands a complete knowledge of normal and variable anatomy of coronary artery, therefore the present study was undertaken.Variations of coronary arteries mentioned in the present study along with new variant of myocardial bridge makes this study of paramount importance in management of heart disease for cardiac surgeons and variant anatomy for anatomists.ABBREVIATIONS Cx-Circumflex CA-Coronary Artery LAD-Left Anterior Descending Lt -Left LCA-Left Coronary Artery Mm-Millimeter PIVA-Posterior Interventricular Artery RCA-Right Coronary Artery Rt-Right STJ-Sinotubular Junction SA na-Sino Atrial Nodal Artery

Table 1 :
Location of Ostia of Rt & Lt coronary arteries.
Left coronary dominance was observed in 13.3% and co-dominance in 3.3 %.( fig-3) During the study we have observed variation in the course of RCA, immediately after its origin trunk of RCA presented 'U' shaped loop (fig-4) .Left coronary artery: Trunk of LCA normally terminates by dividing into left anterior descending and circumflex branches; in this study we observed variations in the termination and number of branches of LCA

Table 3 :
Variations in the division & length of LCA.

Table 4 :
variations observed in the branches of bifurcation of LCA.

Table 5 :
Dominant pattern observed by various authors.
Vandana Ravi, Tejesh S. ANATOMICAL VARIATION IN BRANCHING PATTERN AND DOMINANCE IN CORONARY ARTERIES: A CADAVERIC STUDY.

Table 6 :
Termination of trunk of LCA.