Dissertation on
MORPHOMETRIC STUDY OF THE ARCH OF AORTA AND ITS BRANCHES WITH ITS CLINICAL SIGNIFICANCE
Submitted in partial fulfillment for M.D. DEGREE EXAMINATION BRANCH- XXIII, ANATOMY
Upgraded Institute of Anatomy
Madras Medical College and Rajiv Gandhi Government General Hospital,
Chennai - 600 003
THE TAMILNADU Dr. M. G. R. MEDICAL UNIVERSITY CHENNAI – 600 032
TAMILNADU
MAY-2019
CERTIFICATE
This is to certify that this dissertation entitled “MORPHOMETRIC STUDY OF THE ARCH OF AORTA AND ITS BRANCHES WITH ITS CLINICAL SIGNIFICANCE” is a bonafide record of the research work done by Dr. S. ELAVAR KUZHALI, Post graduate student in the Institute of Anatomy, Madras Medical College and Rajiv Gandhi Government General Hospital, Chennai-03, in partial fulfillment of the regulations laid down by The Tamil Nadu Dr. M. G. R. Medical University for the award of M.D. Degree Branch XXIII-Anatomy, under my guidance and supervision during the academic year from 2016 -2019.
The Dean,
Madras Medical College,
Rajiv Gandhi Govt. General Hospital, Chennai – 600 003.
Dr. Sudha Seshayyan, M.S., Director & Professor,
Institute of Anatomy, Madras Medical College, Chennai– 600 003.
ACKNOWLEDGEMENT
I wish to express exquisite thankfulness and gratitude to my most respected teacher, guide Dr. Sudha Seshayyan, Director and Professor, Institute of Anatomy, Madras Medical College, Chennai - 3, for their invaluable guidance, persistent support and quest for perfection which has made this dissertation take its present shape.
I am thankful to Dr. R. Jayanthi, the Dean, Madras Medical College, Chennai – 3 for permitting me to avail the facilities in this college for performing this study.
My heartfelt thanks to, Dr.V.Lokanayaki and Dr.B.Santhi, Dr.
J.Sreevidya, Dr.Elamathi Bose, Dr.S.Arrchana, Dr.B.J.Bhuvaneshwari, Dr.B.Mohanapriya, Dr.S.Keerthi, Dr.P.R.Prefulla, Dr.N.Sridharan, Dr.S.Nirmala, Dr. M.K.Punitha Rani, Dr.N.Bama, Dr.K.Lavanya Devi, Assistant Professors, and Dr.N. Sridharan, Dr. S. Nirmala Devi, Tutors, Institute of Anatomy, Madras Medical College, Chennai – 3 for their valuable suggestions and encouragement throughout the study.
I earnestly thank my seniors, Dr.V.Srinivasan, Dr.S.Saravanan, Dr.K.Suganya and Dr.G.Gohila who have been supportive and encouraging throughout the study.
I extend my heartfelt thanks to my colleagues Dr.H.Geetha Sangeetha, Dr.P.mythili and Dr.P.Soundraya for their constant encouragement and unstinted co-operation.
I am especially thankful to Mr.R.A.C.Mathews and Mr. E.Senthilkumar, technicians, who extended great support for this study and all other staff members including Mr.Jagadeesan, Mr.Maneesh Mr.Narasimhalu and Mr. Devaraj for helping me to carry out the study.
I thank my parents who have showered their choicest blessings on me and supported me in my every step.
I am grateful beyond words to my husband and son who in all possible ways supported me in making this study a reality.
Above all, I thank the Almighty, who has showered his blessings on me and helped me complete this study successfully.
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“MORPHOMETRIC STUDY OF THE ARCH OF AORTA AND ITS BRANCHES WITH ITS CLINICAL SIGNIFICANCE” of the candidate DR. S. ELAVARKUZHALI with registration number 201633001 for the award of M.D in the branch of ANATOMY.
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CONTENTS
SL.NO TITLE PAGE NO
1. INTRODUCTION 1
2. AIM OF THE STUDY 8
3. REVIEW OF LITERATURE 10
4. EMBRYOLOGY 24
5. MATERIALS AND METHODS 38
6. OBSERVATION 40
7. DISCUSSION 53
8. CONCLUSION 77
9. BIBLIOGRAPHY 80
LEGENDS
1. BRACHIOCEPHALIC TRUNK - BT 2. LEFT COMMON CAROTID ARTERY - LCCA 3. RIGHT COMMON CAROTID ARTERY - RCCA 4. RIGHT SUBCLAVIAN ARTERY - RSA 5. LEFT SUBCLAVIAN ARTERY - LSA
6. ARCH OF AORTA - AA
7. COMMON CAROTID ARTERY - CCA
8. ABERRANT RIGHT SUBCLAVIAN ARTERY - ARSA 9. THYROIDEAE IMA ARTERY - TIA 10. LEFT VERTEBRAL ARTERY - LVA
Introduction
1
INTRODUCTION
The term Aorta is derived from the Greek word aeiro, which means to raise. The arch of aorta (Arcus Aortae) or the aortic arch is the largest and most important artery of our body. It lies in the superior mediastinum opposite to the lower half of manubrium sternum.
The AA begins behind the right half of the manubrium sternum as a continuation of the ascending aorta, in level with the upper border of the right second sternocostal joint. It first ascends diagonally back and to the left over the anterior surface of trachea and finally descends to the left of the body of fourth thoracic vertebra. It ends by continuing as the descending thoracic aorta in the same horizontal plane as its origin at the level of left second costal cartilage49. Its upper limit is seen at the middle of manubrium sternum and the most convex point of the arch lies 2.5cm from the upper border of manubrium sternum49. Hence, the AA has three segments namely ascending, horizontal and descending segments.
2 Fig No.1
RELATIONS:
The AA is related anteriorly and to the left by the left vagus nerve and left phrenic nerve, left superior intercostal vein, superior cervical cardiac branch of the left sympathetic trunk and the inferior cervical cardiac branch of the left vagus nerve, posteriorly and to the right it is related to trachea, oesophagus, superior vena cava, vertebral column, thoracic duct ,the left recurrent laryngeal nerve and the deep cardiac plexus, superiorly by the brachiocephalic artery, the left common carotid artery, the left subclavian artery and the left brachiocephalic vein,
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inferiorly it is related to the bifurcation of pulmonary trunk, left principal bronchus, ligamentum arteriosum and the left recurrent laryngeal nerve49.
Fig No.2
The Ligamentum arteriosum (Botallo’s ligament):
During embryonic development, a horizontally oriented channel called ductus arteriosus is seen arising from the AA beyond the origin of left subclavian artery. It connects the left pulmonary artery with the concave inferior surface of the AA. After birth, the ductus arteriosus becomes obliterated and replaced by fibrous ligamentum arteriosum. The left recurrent laryngeal nerve hooks around it, the superficial cardiac plexus lies anterior to it and the deep cardiac plexus was on the right between the AA and bifurcation of pulmonary trunk.
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The AA gives rise to three branches arising from its convex surface:
1. The Brachiocephalic Trunk (BT) or The Innominate Artery or The Truncus brachiocephalicus, the largest branch which in turn subdivides into Right Common Carotid Artery(RCCA) and Right Subclavian Artery (RSA).
2. The Left Common Carotid Artery (LCCA) or The Arteria carotis communis sinister.
3. The Left Subclavian Artery (LSA) or The Arteria subclavia sinister.
THE BRACHIOCEPHALIC TRUNK:
The BT is the largest among the three branches of the AA. It arises from the convexity of the AA posterior to the middle of manubrium, then it ascends posterolaterally to the right initially anterior to trachea and then to the right. At the level of the right sternoclavicular joint, it terminates by subdividing into right common carotid artery and right subclavian artery49. Sometimes, it may also give rise to thyroideaima artery, thymic artery and bronchial arteries.
THE COMMON CAROTID ARTERIES:
These arteries are the main source of blood supply to head and neck region.
RCCA and LCCA differ in their length and origin. Normally,RCCA arises from the BT and LCCA arises directly from the AA.
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THE RIGHT COMMON CAROTID ARTERY:
The RCCA is entirely cervical in course, arises from the BT behind the right sternoclavicular joint and then ascends upwards to reach the neck and thereafter the course is found similar to that of LCCA.
THE LEFT COMMON CAROTID ARTERY:
The LCCA normally arises as a second direct branch from the AA and its course is divided into two parts, thoracic part and cervical part.
THORACIC PART:
It arises from the highest part of the AA immediately posterolateral to the brachiocephalic trunk and ascends up to the level with left sternoclavicular joint and then enters the neck.
CERVICAL PART:
Both common carotid arteries have similar cervical course. Each artery ascends laterally from behind the sternoclavicular joint up to the level of upper border of thyroid cartilage where it ends by dividing into external and internal carotid arteries.
THE SUBCLAVIAN ARTERIES:
RSA arises from the brachiocephalic trunk and the left subclavian artery originates directly from the AA. The course of each subclavian artery is subdivided into three parts by the scalenus anterior muscle from the site of origin to the outer border of first rib which then continues as axillary artery49. The course
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of the first part of RSA and LSA varies but the second and third parts of the artery are similar in course. Each artery arches over the cervical pleura and apex of lung and has an average diameter of 7mm to 10mm.
FIRST PART OF THE RIGHT SUBCLAVIAN ARTERY:
The artery arises just posterior to the upper border of right sternoclavicular joint from where it ascends to the neck 2cm above clavicle and runs up to the medial margin of scalenus anterior muscle.
FIRST PART OF THE LEFT SUBCLAVIAN ARTERY:
The artery arises from the AA distal to the LCCA, at the level of intervertebral disc between the third and fourth thoracic vertebrae, and then ascends in the neck and arches laterally to reach the medial border of scalenus anterior muscle.
SECOND PART OF THE RIGHT AND LEFT SUBCLAVIAN ARTERIES:
This part of artery lies behind the scalenus anterior muscle. It forms the shortest and the highest part of the artery.
THIRD PART OF RIGHT AND LEFT SUBCLAVIAN ARTERIES:
This part of the artery descends towards the lateral border of scalenus anterior towards the outer border of first rib and ends by continuing as axillary artery. It forms the most superficial part of the artery and courses in the supraclavicular triangle and its pulsations can be felt at this site49.
Most of the anomalies of the arch and its branches are due to the altered development of primitive aortic arches of the embryo during early gestation period. This includes anomalies related to the AA development or variations in the branching patterns. Some of them noted are double AA, inverted AA, right
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AA, common origin of brachiocephalic trunk and left common carotid artery, direct origin of left vertebral artery from the AA and presence of bicarotid trunk giving rise to both right and left common carotid arteries55.
All these anomalous arch variations become clinically significant when they compress the adjacent mediastinal structures such as trachea, esophagus causing dyspnea, dysphagia and recurrent respiratory tract infections. The anomalies of the AA are found frequently associated with congenital heart defects such as tetralogy of fallot, endocardial cushion defects such as atrial and ventricular septal defects, patent ductus arteriosus, truncus arteriosus, double outlet right ventricle.
The knowledge of the normal and variant branching pattern of the AA are significant for diagnostic and therapeutic surgeries of head and neck and thoracic regions.
Aim of the study
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AIM OF THE STUDY
The aim of the study is to measure the dimensions of the arch of aorta and its branches.
The purpose of the present study is to observe the branching pattern of the arch of aorta.
The knowledge of the dimensions of the arch of aorta and its great vessels will be helpful for cardiothoracic surgeons in determining catheter size in AA reconstructive surgeries and four vessel angiographic studies, ligation of aneurysms and treatment of aortic dissection, for vascular surgeons during closure of patent ductus arteriosus, for interventional radiologists to avoid incorrect shunt placement during carotid endarterectomy.
The determination of developmental anomalies of the AA and its branching pattern will be essential for cardiologists to look for coexistent congenital cardiac malformations like bicuspid aortic valve and coarctation of aorta, for neurosurgeons in diagnosing vertebral artery dissection and subarachnoid hemorrhage, for gastroenterologists in treating cases of chronic dysphagia, for otorhinolaryngologists while performing emergency percutaneous tracheostomy to avoid damage to the brachiocephalic trunk of anomalous origin.
9 The parameters noted in this study are
1. The diameter of the aortic arch(AA) at its beginning.
2. The diameter of the aortic arch(AA) at its termination.
3. The diameter of the brachiocephalic trunk(BT) at the level of origin from the aortic arch(AA).
4. The diameter of the left common carotid artery (LCCA) at the level of origin from the aortic arch(AA).
5. The diameter of the left subclavian artery (LSA) at the level of origin from the aortic arch(AA).
6. The distance of the brachiocephalic trunk(BT) from its origin to midline.
7. The distance of the left common carotid artery(LCCA)from its origin to midline.
8. The distance of the left subclavian artery(LSA) from its origin to midline.
9. The angle between the origin of the brachiocephalic trunk(BT) and the aortic arch(AA).
10. The angle between the origin of the left common carotid artery(LCCA) and the aortic arch(AA).
11. The angle between the origin of the left subclavian artery(LSA) and the aortic arch(AA)
12. To observe the branching pattern of the aortic arch(AA) and its variations.
Review of Literature
10
REVIEW OF LITERATURE
I. DIAMETER OF THE AA AT ITS BEGINNING
1. Henry Gray49(1827) stated that the diameter of the AA at its beginning was 28 mm.
2. Testut53 (1929) described that the diameter of the AA was maximum at its beginning which was found to be 30mm.
3. Paturet39 (1958) quoted that the diameter of the AA was 25mm at its beginning.
4. Bouchet13 (1991) described that the mean diameter of the AA at its beginning was 30mm.
5. Nguyen35 (1994) stated that 30mm was the diameter of the AA at its beginning.
6. Gorun19 (2010) stated that 28mm was the diameter of the AA at its beginning.
7. Herrera et al23 (2012) found in his study on 87 cadavers that the mean diameter of the AA at its beginning was 30.1mm.
II.DIAMETER OF THE AA AT ITS TERMINATION.
1. Henry Gray49 (1827) stated that the diameter of the AA at its termination was 20 mm.
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2. Testut54 (1929) described that the diameter of the AA at its termination was between 18 to 20 mm.
3. Paturet39 (1958) quoted that the diameter of the AA was between 18 to 20mm at its termination.
4. Nguyen35 (1994) stated that the AA diameter at its termination was between 18 to 20mm.
5. Bouchet13 (1991) described the diameter of the AA at its termination was 20mm.
6. Gorun19 (2010) described that the diameter of the AA at its termination was 22mm.
7. Herrera et al23 (2012) reported in his study on 87 cadavers that the mean diameter of the AA at its termination was 20.1mm.
III. DIAMETER OF THE BRACHIOCEPHALIC TRUNK AT THE LEVEL OF ORIGIN FROM THE AA
1. Testut53 (1929) described that the diameter of BT was between 12 to 15mm at the level of origin from the AA.
2. Paturet39 (1958) observed the diameter of the BT at its origin as 13mm.
3. Wright et al56 (1969) in his study on 50 cadavers that the mean diameter of the BT was 12.5mm at its origin from the AA.
4. Bouchet13 (1991) described that the diameter of the BT was 13mm at the level of origin from the AA.
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5. Grande et al20 (1995) in his study on 33 cadavers reported that the mean diameter of the BT at its origin was 11.2mm.
6. Kamina27 (2002) stated that the diameter of the BT at its origin was 13mm.
7. Shin et al46 (2008) reported in his cadaveric study on 25 cadavers that the mean diameter of the BT was found to be 18.3mm at its origin.
8. Alsaif et al3 (2010) observed in his study on 35 cadavers that 17.97mm was the mean diameter of the BT at its origin.
9. Gorun19 (2010) stated that the mean diameter of the BT at its origin was 14mm.
10. Herrera et al23 (2012) observed in his study on 87 cadavers that the mean diameter of the BT at its origin was 9.7mm.
11. Kamalkant Chhabra et al28 (2015) performed a study on 60 cadavers in which the mean diameter of the BT was found to be 9.4mm at its origin.
12. Junagade et al26 (2015) in his study on 35 cadavers observed that the mean diameter of the BT at its origin was 13mm.
IV. DIAMETER OF THE LEFT COMMON CAROTID ARTERY AT THE LEVEL OF ORIGIN FROM THE AA:
1. Paturet39 (1958) stated that the mean diameter of the LCCA at its origin was 9 to 10mm.
2. Bouchet13 (1991) described that the diameter of the LCCA was 8mm at its origin.
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3. Grande et al20 (1995) in his study on 33 cadavers reported that the mean diameter of the LCCA at its origin was 8.5mm.
4. Turgut54 (2001) in his case report of a 21year old female cadaver reported that the diameter of LCCA at its origin was 13mm.
5. Kamina27 (2002) described that the diameter of LCCA was 9mm at its origin.
6. Shin et al46 (2008) in his study on 25 cadavers noticed that the mean diameter of the LCCA at its origin was 9.8mm.
7. Alsaif et al3 (2010) in his study on 35 cadavers found that 9.7mm was the mean diameter of the LCCA at its origin.
8. Gorun19 (2010) quoted the diameter of the LCCA at its origin as 9mm.
9. Herrera et al23 (2012) in his study on 87 cadavers, observed that the mean diameter of LCCA was 6.3mm at its origin.
10. Kamalkant Chhabra et al28 (2015) in his study on 60 cadavers reported that the mean diameter of LCCA was 6.4mm at its origin.
V. DIAMETER OF THE LEFT SUBCLAVIAN ARTERY AT THE LEVEL OF ORIGIN FROM THE AA
1. Paturet39 (1958) stated that the diameter of the LSA at its origin was between 9 to 10mm.
2. Bouchet13 (1991) described that the diameter of the LSA at its origin was between 9 to 10mm
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3. Grande et al20 (1995) conducted a study in 33 cadavers and found that the mean diameter of the LSA was 8.8mm at its origin.
4. Kamina27 (2002) observed that the diameter of the LSA at its origin was between 9 to 10mm.
5. Shin Young et al46 (2008) in his study on 25 cadavers reported that the mean diameter of the LSA was 10.6mm at its origin.
6. Alsaif et al3 (2010) in his study on 35 cadavers reported that the mean diameter of the LSA at its origin was 14.33mm.
7. Gorun19 (2010) stated that the diameter of the LSA at its origin was 10mm.
8. Herrera et al23 (2012) in his study on 87 cadavers found that the mean diameter of the LSA at its origin was 7.6mm.
9. Kamalkant Chhabra et al28 (2015) in his study on 60 cadavers reported that the mean diameter of the LSA was 7.62mm at its origin.
VI. ANGLE BETWEEN THE ORIGIN OF THE BRACHIOCEPHALIC TRUNK WITH THE AA
1. Zamir et al60 (1991) in 40 cadavers reported that the angle between the origin of the BT and the AA was 54⁰.
2. Shin Young et al46 (2008) in his study on 25 cadavers observed that the origin of the BT makes an angle of 65⁰ with AA.
3. Junagade.B et al26 (2015) in his study on 35 cadavers observed that the angle between the origin of the BT and the AA was 88⁰.
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4. Kamalkant Chhabra et al28 (2015) in 60 cadavers reported that the angle between the origin of the BT and the AA was 94⁰.
VII. ANGLE BETWEEN THE ORIGIN OF THE LEFT COMMON CAROTID ARTERY AND THE AA
1. Zamir et al60 (1991) in 40 cadavers observed that the angle between the origin of the LCCA and the AA was 58⁰.
2. Shin Young et al46 (2008) conducted a study in 25 cadavers and reported that the origin of the LCCA makes an angle of 46 ⁰ with the AA.
3. Kamalkant Chhabra et al28 (2015) in 60 cadavers observed that the angle formed between the origin of the LCCA and the AA was 82⁰.
4. Junagade.B et al26 (2015) in his study on 35 cadavers found that the LCCA makes an angle of 46 ⁰with the AA.
VIII. ANGLE BETWEEN THE ORIGIN OF LEFT SUBCLAVIAN ARTERY AND THE AORTIC ARCH
1. Zamir et al60 (1991) in 40 cadavers observed that the origin of the LSA made an angle 64 ⁰ with the aortic arch.
2. Shin Young et al46 (2008) conducted a study in 25 cadavers and observed that the angle between the origin of the LSA and the AA was 63⁰.
3. Kamalkant Chhabra et al28 (2015) performed a study in 60 male cadavers and reported that the angle between the origin of the LSA and the AA was 99 ⁰.
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4. Junagade.B et al26 (2015) in his study on 35 cadavers observed that the angle between the origin of the LSA and the AA was 50⁰.
IX. DISTANCE OF ORIGIN OF THE BRACHIOCEPHALIC TRUNK FROM MIDLINE
1. Shin Young et al46 (2008) performed a study in 25 cadavers and found that the BT was situated at a distance of 0.92mm to the right of midline.
2. Alsaif et al3 (2010) in his study on 30 cadavers and reported that the BT originated at a distance of 9.33mm to the right of midline.
3. Junagade et al26 (2015) conducted a study in 35 cadavers and observed that in 10 cadavers the BT originated 4.3mm to the left of midline while in 2 cadavers it originated at midline. In the rest of cadavers, it was found to arise 6mm to the right of midline.
4. Kamalkant Chhabra et al28 (2015) in his study on 60 cadavers found that the BT was situated 5.9mm to the right of midline.
X. DISTANCE OF ORIGIN OF THE LEFT COMMON CAROTID ARTERY FROM MIDLINE
1. Shin Young et al46 (2008) conducted a study on 25 cadavers and found that the origin of the LCCA was situated at a distance of 12mm to the left of midline
2. Alsaif et al3 (2010) in his study on 30 cadavers reported that the origin of the LCCA was present at a distance of 15mm to the left of midline.
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3. Junagade et al26 (2015) studied in 35 cadavers and observed that the LCCA was originated 16mm to the left of midline.
4. Kamalkant Chhabra et al28 (2015) performed a study in 60 cadavers and found that the LCCA was situated 18mm to the left of midline.
XI. DISTANCE OF ORIGIN OF THE LEFT SUBCLAVIAN ARTERY FROM MIDLINE
1. Shin Young et al46 (2008) conducted a study on 25 cadavers and found that the LSA was situated at a distance of 29mm to the left of midline.
2. Alsaif et al3 (2010) in 30 cadavers observed that the LSA was originated at a distance of 33 mm to the left of midline.
3. Junagade et al26 (2015) in his study on 35 cadavers reported that the LSA was originated 32.4mm to the left of midline.
4. Kamalkant Chhabra et al28 (2015) in his study on 60 cadavers reported that the LSA was situated 30mm to the left of midline.
XII. VARIATIONS IN THE DEVELOPMENT OF THE AORTIC ARCH AND ITS BRANCHING PATTERN
1. Hommel24 (1737) described about the presence of double aortic arch in adult human cadavers.
2. Thompson et al54 (1893) observed nine types of variant branching patterns of the aortic arch:
Type 1- Normal branching pattern.
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Type 2- Common trunk of origin of BT and LCCA.
Type 3-Left vertebral artery as a direct branch from the AA.
Type 4- Presence of aberrant right subclavian artery as a direct branch from the AA.
Type 5-Presence of biinnominate arteries.
Type 6- Common trunk of origin of LCCA and LSA.
Type 7-RSA, LVA, common stem for LCCA and RCCA.
Type 8-RCCA, LCCA, LSA and RSA.
Type 9- Type 1 pattern with additional branches like TIA.
3. Adachi B. Das2 (1928) described four types of branching pattern of the AA:
Type A - Normal branching pattern (83.3%).
Type B - Bovine arch pattern with common trunk of origin of the brachiocephalic trunk and the left common carotid artery (10.9%).
Type C -Vertebral pattern of the aortic arch in which the LVA arises directly from the aortic arch between the origin of the LCCA and the LSA rather than from the RSA (4.3%).
Type G- Aberrant right subclavian artery arising directly from the AA as a last branch with retro oesophageal course (0.8%).
4. Anson and McVay4 (1971) described fifteen different types of branching pattern of the AA.
Type 1 -Normal branching pattern.
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Type 2 –Common trunk of origin of the BT and the LCCA.
Type 3 –LVA arising as a direct branch from the AA between LCCA and LSA.
Type 4- RSA, LVA, common stem for LCCA and RCCA.
Type 5 -LVA arising from the BT, LSA, RSA.
Type 6 -Aberrant origin of the right subclavian artery, LVA arising as a direct aortic branch.
Type 7-Aberrant right subclavian artery with BA.
Type 8-Aberrant right subclavian artery with common stem for both carotid arteries.
Type 9 – Presence of biinnominate arteries giving rise to paired vessels.
Type 10-LVA arising in common with the LSA.
Type 11-Common trunk for BT and LCCA and common trunk for LVA and LSA.
Type 12- Normal branching pattern with an additional artery called as thyroidea ima artery.
Type 13-All the three branches arise from a single common trunk.
Type 14 -Similar to type 13 with LVA arising separately from the aortic arch.
Type 15-Presence of the right aortic arch with mirror image type.
5.Anson and Mc Donald5 (1940) studied in 157 cadavers and found that 66.9%
had normal branching pattern, 25.5% had bovine arch pattern and 1.46% had vertebral pattern of aortic arch as per Adachi′s classification.
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6. Anson and Mc Donald5 (1940) noticed in 59 cadavers that 51.7% had normal branching pattern ,41.4% had bovine arch pattern and 1.7% had aberrant right subclavian artery as per Adachi′s classification.
7. Nelson and Sparks et al35 (2001) observed in 193 cadavers that normal branching pattern was seen in 94%, BA pattern in 3.5%, vertebral pattern in 0.7% and aberrant right subclavian artery in 0.7% as per Adachi′s classification.
8. Bahman Jalali Kondori et al6 (2005) in his radiological study on 226 patients found that 12.4 % had bovine arch pattern and 1.8% had aberrant right subclavian artery as per Adachi′s classification.
10. Soubhagya.R Nayak et al34 (2006) in 62 cadavers observed that 91.4% had normal branching pattern, 4.8% had common origin of LCCA and the BT, 1.6% had biinnominate pattern with left coronary artery arising directly from the aortic arch, 1.6% had aberrant right subclavian artery arising directly from the AA and 1.6% had LVA arising directly from the AA.
11. Shetty et al46 (2006) observed a rare anomaly during routine dissection that there existed a coexistence of three anatomic variations such as common trunk for BT and LCCA, coarctation of aorta, LVA arising as a direct aortic branch.
12. Shin Young et al48 (2008) in his study on 25 cadavers observed that 84%
had normal branching pattern, 8% had bovine arch pattern and 8% had the vertebral pattern of aortic arch as per Adachi′s classification.
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13. Natsis et al33 (2009) in his study on 633 cadavers reported that 83% had normal branching pattern,15% had bovine arch pattern,0.79% had vertebral pattern of aortic arch and 0.16% had aberrant right subclavian artery as per Adachi′s classification.
14. Bhattarai et al11 (2010) in 85 cadavers observed that 80% had normal branching pattern, 12.9% had bovine arch pattern and 7% had vertebral pattern of aortic arch as per Adachi′s classification.
15. Mange et al32 (2011) in a case report of a 41year old male observed that 67.3
% had normal branching pattern and 25.7% had bovine arch pattern as per Adachi′s classification.
16. Herrera et al23 (2012) performed a study on 87 cadavers and observed eight different types of branching pattern of the AA:
Type 1-Normal branching pattern (74.72%).
Type 2-Common origin of LCCA and LSA (2.84%).
Type 3-Origin of LSA from the BT (2.14%).
Type 4-RCCA, LCCA, LSA and aberrant right subclavian artery (0.55%).
Type 5-Similar to type 4 with double or right sided aortic arch (0.24%).
Type 6-Aortic origin of LVA (3.63%).
Type 7-Aortic origin of RVA (0.24%).
Type 8-Aortic origin of TIA (2.22%).
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17. Faizal et al16 (2012) in 30 cadavers reported that 84% had normal branching pattern and 16.6% had vertebral pattern of aortic arch as per Adachi′s classification.
18. Sumita Tulsidas Patel et al50 (2012) in 75 cadavers reported that 77.3% had normal branching pattern, 14.66% had bovine arch pattern and 8% had vertebral pattern of aortic arch as per Adachi′s classification.
19. Mamatha et al30 (2013) conducted a study on 40 cadavers and found that 85% had normal branching pattern, 2.5% had bovine arch pattern, 10% had vertebral pattern of aortic arch and 2.5% had aberrant right subclavian artery as per Adachi′s classification.
20. Acar et al1 (2013) dissected 94 cadavers and noticed seven different types of branching pattern of the aortic arch:
Type 1- Normal branching pattern (74.46%).
Type 2- Bovine arch pattern (14.91%).
Type 3 -RCCA, LCCA, LSA and RSA (2.13%).
Type 4- BT, LCCA, LVA and LSA (2.13%).
Type 5 –BT and LCCA arising as common trunk, LVA and LSA as common trunk (1.06%).
Type 6 - RCCA and LCCA as common stem, LSA and RSA (1.06%).
21. Virendra Budhiraja et al55 (2013) conducted a study in 52 cadavers and found had vertebral pattern of aortic arch and 1.9% had three branches such as the common trunk, LVA and LSA.
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22. Rekha et al41 (2013) performed a study in 110 cadavers reported that 92.72% had normal branching pattern, 2.72% had bovine arch pattern and 4.5% had vertebral pattern of aortic arch as per Adachi′s classification.
23. Radhakrishna Shetty et al40 (2014) in 50 cadavers observed that 76% had normal branching pattern, 16% had bovine arch pattern and 8% had vertebral pattern of aortic arch as per Adachi′s classification.
24. Duraipandian et al15 (2014) dissected 30 cadavers and reported 63.33% had normal branching pattern, 33.33% had bovine arch pattern and 3.33 % had vertebral pattern of aortic arch as per Adachi′s classification.
25. Junagade et al26 (2015) performed a study in 35 cadavers and reported that 88.57 % had normal branching pattern,8.58% had bovine arch pattern and 2.85% had vertebral pattern of the aortic arch as per Adachi′s classification.
26. Gavishiddappa A.et al18 (2015) performed a study on 30 cadavers and found that 86.6% had normal branching pattern,10% had vertebral pattern of the aortic arch and 3.33% had two branches from the arch namely the BT and common trunk for LCCA and the LSA.
Embryology
24
EMBRYOLOGY
DEVELOPMENT OF THE ARCH OF AORTA AND ITS BRANCHES:
The development of the AA and its branches takes place around fourth to fifth week of intrauterine period. The mesenchymal cells in the cardiogenic area located between the septum transversum and prochordal plate in the trilaminar germ disc of the developing embryo condenses to form two endothelial heart tubes. These tubes fuse in a cranio caudal direction to form a single heart tube.
But the caudal parts of the two tubes fails to fuse with each other and remains bifurcated. The heart tube forms five dilatations. From cranial to caudal direction, they are truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium and sinus venosus44.
The arteries of the body develop from two main sources such as pharyngeal or aortic arch arteries and the dorsal aorta. The pharyngeal arch arteries give rise to arteries of head and neck region and dorsal aorta gives rise to the arteries of rest of the body. First arteries to appear in a developing embryo are the right and left primitive aortae which appears in the flattened embryonic area prior to the formation of embryonic folds. Simultaneously, six bars of pharyngeal arches are formed in the lateral wall of the pharynx of which the fifth arch usually disappears. With the formation of head fold of embryo, the right and left primitive aortae bend ventrally along the lateral wall of pharynx through the mesodermal core of first pair of pharyngeal arches and communicates with the heart tube29.
25
Each primitive aorta is divided into three parts, the part lying ventral to foregut is called the ventral aorta, the part dorsal to gut is the dorsal aorta and the arched portion connecting the ventral and the dorsal aorta is the first aortic arch artery.
THE VENTRAL AORTA
Just cephalic to the bulbus cordis, the two ventral aortae fuse to form the truncus arteriosus which then dilates to form the aortic sac. The distal part of the aortic sac bifurcates into right limb and left limb and each limb of aortic sac is connected to the corresponding dorsal aorta through the first aortic arch which is the continuation of the primitive aorta. Finally, there are six pairs of arteries called aortic arch arteries developing from the aortic sac which pass laterally around the foregut in the lateral wall of pharynx extending from the dorsal aorta to the ventral aorta44. In human embryos, all the aortic arch arteries are never present at the same time. Their formation and remodeling shows a pronounced cranio caudal gradient. The more cranial ones are in the process of regression before the caudal ones completely appear29.
THE DORSAL AORTA
The two dorsal aortae fuse caudo cranially to form a single aorta. The aortic arch pattern may be considered in two phases, branchial phase and post branchial phase. In the branchial phase, six pairs of aortic arches are not present all at a time. Fifth arch is transitory and disappears early. Due to caudal shift of heart, most of the parts of first and second pair of aortic arches start regressing
26
with the remaining parts forming maxillary and stapedial artery respectively.
Associated with the regression of first and second aortic arches, a new vessel external carotid artery sprouts cranially from the aortic sac close to the origin of the third aortic arch following which the origin of the artery is incorporated with third aortic arch. In order to supplement the growing upper limb bud, seventh cervical intersegmental artery sprouts outwards from each dorsal aorta distal to the attachment of the sixth aortic arch. Then each sixth arch artery gives out a pulmonary bud on either side and hence the sixth arch is also called as the pulmonary arch44.
Fig no :3
27
In the post branchial phase, many important events occur leading to the development of the definitive aortic arch and its great vessels.
1. The portion of the dorsal aorta between the third and fourth arches regresses on each side to form ductus caroticus. Hence the dorsal part of the third aortic arch distal to the origin of the external carotid artery and the dorsal aorta cephalic to it forms the INTERNAL CAROTID ARTERY. The ventral part of the third aortic arch together with the elongation of aortic sac forms the COMMON CAROTID ARTERY.
2. The ventral part of the right sixth aortic arch forms the right pulmonary artery and its dorsal part regresses and disappears thus losing its contact with the dorsal aorta. In a similar manner, the ventral part of the left sixth aortic arch forms the left pulmonary artery while its dorsal part regresses to form DUCTUS ARTERIOSUS After birth, the ductus arteriosus gets fibrosed to form the LIGAMENTUM ARTERIOSUM which connects the left pulmonary artery with the undersurface of arch of aorta.
3. The portion of the right dorsal aorta caudal to the origin of seventh intersegmental artery disappears up to the fusion of the two dorsal aorta.
4. The right fourth aortic arch, the part of right dorsal aorta caudal to ductus caroticus along with right seventh intersegmental artery forms the RIGHT SUBCLAVIAN ARTERY.
28
5. The right limb of the aortic sac which is connected with third and fourth aortic arches persists as the BRACHIOCEPHALIC TRUNK.
6. The vertebral artery is formed by the development of longitudinal anastomosis that links the dorsal cervical intersegmental arteries. All the intersegmental arteries regress except for the seventh artery which becomes the point of origin of vertebral artery.
7. The left seventh intersegmental artery persists as the LEFT SUBCLAVIAN ARTERY. It is found that the origin of this artery shifts more cranially close to the origin of left common carotid artery cranial to the attachment of the ductus arteriosus, due to the descent of heart.
8. On the left side, the DEFINITIVE ARCH OF AORTA is formed from three sources such as the left limb of aortic sac, the left fourth aortic arch and the left dorsal aorta44.
A. The left limb of the aortic sac
This forms the part of the aortic arch between the origins of brachiocephalic trunk and the left common carotid artery.
B. The left fourth aortic arch
This forms that part of the aortic arch between the origins of left common carotid and left subclavian arteries. It is found that the ductus arteriosus is attached to the undersurface of this part of the aortic arch.
29 C. The left dorsal aorta
This forms the distal part of aortic arch and extends up to the fourth thoracic segment where the two dorsal aortae fuse with each other.
Fig no 4
30
DEVELOPMENTAL ANOMALIES OF THE AORTIC ARCH:
THE DOUBLE AORTIC ARCH:
In this anomaly, there is persistence of the right dorsal aorta distal to the origin of the right seventh intersegmental artery and its junction with the left dorsal aorta. This leads to the formation of the aortic arch on both the sides. As a result, the right arch of aorta passes behind the trachea and oesophagus while the left arch passes in front of them. Thus a vascular ring is formed between the right and the left aortic arches which compresses the trachea and oesophagus leading to difficulty in breathing and swallowing. The descending aorta is usually seen on the left side. In most of the cases, one arch is dominant most commonly it will be the right aortic arch seen in 70 to 80 percent cases, codominant arch is seen in 5 percent and the left dominant arch is seen in 25 percent cases29.
Fig no:5
31 THE RIGHT AORTIC ARCH
In this anomaly, the left dorsal aorta distal to the origin of left seventh intersegmental artery disappears but the right dorsal aorta persists giving rise to right aortic arch. The right pulmonary artery is connected with the right aortic arch by ductus arteriosus which later becomes ligamentum arteriosum.
Sometimes, the ligamentum arteriosum lies on the left side and passes behind the oesophagus causing difficulty in swallowing. This anomaly is a mirror image of the left aortic arch44
.
Fig no:6
32 THE ABSENT AORTIC ARCH
It is one of the rare anomalies of the aortic arch. In this type, there is no connection between the ascending aorta and the descending aorta, the latter being continuation of the pulmonary trunk via the ductus arteriosus. This is due to the interruption of formation of the aortic arch anywhere between the embryonic aortic sac and the ductus arteriosus29.
THE PATENT DUCTUS ARTERIOSUS
This anomaly occurs due to the persistence of ductus arteriosus which is a connecting channel between the aortic arch and the left pulmonary artery. As a result, there is shunting of blood from the aortic arch back into the pulmonary circulation49. It is one of the most common congenital anomalies of the aortic arch.
Fig no:7
33 THE COARCTATION OF AORTA:
In this type, there is congenital narrowing of the arch of aorta distal to the origin of LSA. It occurs due to the extension of process of obliteration of ductus arteriosus into the aorta. It is of two types, preductal and postductal type. In preductal type, the narrow segment is present proximal to ductus arteriosus which usually persists and in post ductal type, the narrow segment is present distal to ductus arteriosus which obliterates later in development.
Fig no:8
ANOMALIES OF THE BRANCHING PATTERN OF ARCH OF AORTA:
The most common type of variations observed are the common trunk of origin of BT and LCCA, direct origin of the LVA from the AA between the origin of the LCCA and the LSA, presence of the bicarotid trunk and presence of the aberrant origin of the right subclavian artery directly from the AA.
34 THE BOVINE ARCH:
In normal development of the aortic arch, the proximal part of the left third aortic arch absorbs into the left horn of aortic sac forming left common carotid artery. If it gets absorbed into the right limb of aortic sac then it leads to formation of common trunk bearing the brachiocephalic trunk and left common carotid artery and this condition is commonly referred as THE BOVINE ARCH.
Fig no :9
ABNORMAL ORIGIN OF THE LEFT VERTEBRAL ARTERY:
During normal development, the left subclavian artery develops from the seventh cervical intersegmental artery. The first part of the left vertebral artery develops from the dorsal division of left seventh intersegmental artery. This anomaly is due to the persistence of left sixth cervical intersegmental artery and
35
increased absorption of embryonic tissue around the left seventh cervical intersegmental artery up to its dorsal and ventral divisions.
Fig no :10
THE BICAROTID TRUNK
In this anomaly, there exists an abnormal connection between proximal part of the left third aortic arch to the right branch of aortic sac. So both the right common carotid and the left common carotid arise from a common stem giving rise to the formation of bicarotid trunk.
36
THE ABERRANT RIGHT SUBCLAVIAN ARTERY: (ARTERIA SUBCLAVIA DYSPHAGIA LUSORIA)
This anomaly occurs due to the abnormal disappearance of right fourth aortic arch artery along with part of right dorsal aorta cranial to right seventh intersegmental artery. As a result, the part of the right dorsal aorta caudal to seventh intersegmental artery persists and forms the proximal part of right subclavian artery and the distal part of the artery is derived from the right seventh intersegmental artery29.
Fig no :11
37
In the present study three types of variations has been observed:
1. Common trunk of origin of the brachiocephalic artery and the left common carotid artery from the aortic arch commonly called as the Bovine Arch pattern.
2. Presence of aberrant right subclavian artery with retro oesophageal course as a direct aortic branch commonly known as Arteria Subclavia Dysphagia Lusoria
3. Abnormal origin of left vertebral artery directly from the aortic arch between the origins of left common carotid artery and the of left subclavian artery.
GENETICS:
Genetic factors determining the aortic arch development and its branches are now detected The genes like TBX1, UFD1 (Ubiquitin fusion degradation 1, a gene regulated by HAND2) and HIRA (a gene encoding for a protein that interacts with PAX 3) which are present in the chromosome 22q11.2.
Chromosome 22q11.2 microdeletions are also associated with CATCH 22 syndrome, in which conotruncal cardiac defects along with aortic arch anomalies are observed. Cardiac neural crest cells are found to play an important role in the development of inflow and the outflow tracts of the heart and the aortic arch and its branches29.
Materials & Methods
38
MATERIALS AND METHODS
The present study on the AA and its branches is conducted in the Institute of Anatomy, Madras Medical College, Chennai with 50 embalmed adult human cadavers irrespective of age and sex. The study is done over a period of three years from 2016 to 2018.
MATERIALS:
Vernier callipers.
Goniometer.
Measuring tape.
Pins and threads.
METHOD:
CONVENTIONAL DISSECTION METHOD:
The dissection of the AA is carried out as per 16th edition of Cunningham’s manual of practical anatomy. A midline vertical skin incision is made extending from chin to xiphoid process. A transverse incision is extended on either side from the midline immediately below the clavicle up to the acromion process. Skin, superficial fascia and deep fascia are dissected and reflected laterally on either side. In case of female cadavers, mammary glands are dissected and removed on both sides. Underlying pectoralis major and pectoralis minor muscles are also reflected and detached from its origin towards insertion site. The thoracic cage is visualized along with its intercostal muscles. Sternum is
39
disarticulated from the clavicle at sternoclavicular joint. All the ribs forming the anterior wall of thoracic cage are cut along the anterior axillary line. The anterior wall of the rib cage is then turned downwards.
The thoracic cavity is exposed and both the lungs are dissected and removed. The heart with its pericardium and its great vessels namely the brachiocephalic trunk, left common carotid artery, left subclavian artery are seen in the superior mediastinum. Superior vena cava and brachiocephalic veins are cleared and pericardium is uncovered to expose the arch of aorta. All the fibro fatty tissue and nerves are removed from the mediastinum surrounding the heart.
The diameter of the AA at its beginning and termination and its major branches at their level of origin are measured using vernier callipers in millimeters. The distance of the branches from origin to the midline is determined using inch tape in millimeters. The angle formed between the origin of the branches and the AA is calculated using goniometer in degrees. The branching pattern of the arch of aorta is observed.
The branches of the AA are further traced up to the neck by dissecting in the carotid and supraclavicular triangles of neck. The common carotid arteries are traced till its bifurcation into external and internal carotid arteries. The origin and course of subclavian arteries on both sides are traced till the outer border of first rib. The site of origin of the vertebral arteries and its further course in the neck are also noted.
Observation
FIG NO :12 - DIAMETER OF THE AORTIC ARCH AT ITS BEGINNING
AORTIC ARCH AT ITS BEGINNING - AA(B)
BRACHIOCEPHALIC TRUNK - BT
LEFT COMMON CAROTID ARTERY - LCCA
LEFT SUBCLAVIAN ARTERY - LSA
40
OBSERVATION
1. EXTERNAL DIAMETER OF THE AA AT ITS ORIGIN
The external diameter of the AA at its beginning is measured. In the present study, the maximum external diameter of the AA is 41mm, minimum diameter is 21mm and the mean diameter is 31mm. Out of the 50 cadavers dissected, the external diameter of the aortic arch in 14 cadavers (28%) is below the mean value and in 36 cadavers (72%) it is above the mean value.
TABLE NO:1-EXTERNAL DIAMETER OF THE AA AT ITS BEGINNING(mm)
S.
No
Number of cadavers
Maximum diameter of the
AA at its beginning (mm)
Minimum diameter of the
AA at its beginning (mm)
Mean diameter of the AA at its beginning (mm)
1. 50 41 21 31
CHART NO:1- EXTERNAL DIAMETER OF THE AA AT ITS BEGINNING(mm)
41
21
31
0 5 10 15 20 25 30 35 40 45
Maximum diameter Minimum diameter mean diameter
DIAMETER(mm)
FIG NO:13 DIAMETER OF THE AORTIC ARCH AT ITS TERMINATION
AORTIC ARCH AT ITS TERMINATION - AA (T)
BRACHIOCEPHALIC TRUNK - BT
LEFT COMMON CAROTID ARTERY - LCCA
LEFT SUBCLAVIAN ARTERY - LSA
41
2. EXTERNAL DIAMETER OF THE AA AT ITS TERMINATION
The external diameter of the AA at its termination is measured. In the present study, maximum external diameter observed is 33mm, minimum external diameter is 16mm and the mean external diameter is 23mm. Among 50 cadavers dissected,17 cadavers (34%) are below the mean value and 33 cadavers (66%) are above the mean value.
TABLE NO:2- EXTERNAL DIAMETER OF THE AA AT ITS TERMINATION (mm)
S.
no
Number of cadavers
Maximum diameter of the
AA at its termination(mm)
Minimum diameter of the
AA at its termination(mm)
Mean diameter of the AA at its
termination (mm)
1. 50 33 16 23
CHART NO:2 – EXTERNAL DIAMETER OF THE AA AT ITS TERMINATION(mm)
33
16
23
0 5 10 15 20 25 30 35
Maximum diameter Minimum diameter Mean diameter
DIAMETER (mm)
FIG NO:14 DIAMETER OF THE BRACHIOCEPHALIC TRUNK AT ITS ORIGIN
AORTIC ARCH - AA
BRACHIOCEPHALIC TRUNK - BT
LEFT COMMON CAROTID ARTERY - LCCA
LEFT SUBCLAVIAN ARTERY - LSA
42
3. EXTERNAL DIAMETER OF THE BT AT ITS ORIGIN FROM THE AA The external diameter of the BT at the level of origin from the AA is observed. In the present study, the maximum external diameter is found to be 22mm, the minimum external diameter is 9 mm and the mean external diameter is 13 mm. Out of 50 cadavers dissected,18 cadavers (36%) are above the mean value and 32 cadavers (64%) are below the mean value.
TABLE NO:3- EXTERNAL DIAMETER OF THE BT AT ITS ORIGIN FROM THE AA (mm)
S.
No
Number of cadavers
Maximum diameter of BT
(mm)
Minimum diameter of BT
(mm)
Mean diameter of BT
(mm)
1. 50 22 9 13
CHART NO :3- EXTERNAL DIAMETER OF THE BT AT ITS ORIGIN FROM THE AA (mm)
22
9
13
0 5 10 15 20 25
Maximum diameter Minimum diameter Mean diameter
DIAMETER (mm)
FIG NO 15: DIAMETER OF THE LEFT COMMON CAROTID ARTERY AT ITS ORIGIN
AORTIC ARCH - AA
BRACHIOCEPHALIC TRUNK - BT
LEFT COMMON CAROTID ARTERY - LCCA
LEFT SUBCLAVIAN ARTERY - LSA
43
4. EXTERNAL DIAMETER OF THE LSA AT ITS ORIGIN FROM THE AA
The external diameter of the LSA at the level of origin from the AA is measured. In the present study, maximum external diameter measured is 14 mm, the minimum external diameter is 6 mm and the mean external diameter is 9 mm.
Among 50 cadavers dissected ,17 cadavers (34%) are above the mean value and 33 cadavers (66%) are below the mean value.
TABLENO:4- EXTERNAL DIAMETER OF THE LSA AT ITS ORIGIN FROM THE AA (mm)
S.
No
Number of cadavers
Maximum diameter of LSA
(mm)
Minimum diameter of
LSA (mm)
Mean diameter of LSA (mm)
1. 50 14 6 9
CHART NO:4 EXTERNAL DIAMETER OF THE LSA AT ITS ORIGIN FROM THE AA (mm)
14
6
9
0 2 4 6 8 10 12 14 16
Maximum diameter Minimum diameter Mean diameter
DIAMETER (mm)
FIG NO: 16 DIAMETER OF THE LEFT SUBCLAVIAN ARTERY AT ITS ORIGIN
AORTIC ARCH - AA
BRACHIOCEPHALIC TRUNK - BT
LEFT COMMON CAROTID ARTERY - LCCA
LEFT SUBCLAVIAN ARTERY - LSA
44
5. EXTERNAL DIAMETER OF THE LCCA AT ITS ORIGIN FROM THE AA
The external diameter of the LCCA at the level of origin from the AA is measured. From the present study, the maximum external diameter is found to be 11 mm, the minimum external diameter is 5 mm and the mean external diameter is 7.8mm. It is noticed that 15 cadavers (30%) are above the mean value, and 35 cadavers (70%) are below the mean value.
TABLE NO:5- EXTERNAL DIAMETER OF THE LCCA AT ITS ORIGIN FROM THE AA (mm)
S.
no
Number of cadavers
Maximum diameter of LCCA (mm)
Minimum diameter of LCCA (mm)
Mean diameter of LCCA(mm)
1. 50 11 5 7.8
CHART NO:5- EXTERNAL DIAMETER OF THE LCCA AT ITS ORIGIN FROM THE AORTIC AA (mm)
11
5
7.8
0 2 4 6 8 10 12
Maximum diameter Minimum diameter Mean diameter
DIAMETER (mm)
FIG NO:17 DISTANCE OF THE BRACHIOCEPHALIC TRUNK FROM ITS ORIGIN TO MIDLINE
AORTIC ARCH - AA
BRACHIOCEPHALIC TRUNK - BT
LEFT COMMON CAROTID ARTERY - LCCA
LEFT SUBCLAVIAN ARTERY - LSA
45 6. DISTANCE OF THE BT FROM ITS ORIGIN TO MIDLINE
The distance of the BT from its origin to midline is measured. In the present study, the maximum distance of origin of the BT midline is 13 mm, the minimum distance is 3mm and the mean distance is 8mm. Among the 50 cadavers dissected, in 20 cadavers (40%) the distance of origin of the BT is above the mean distance and in 30 cadavers (60%) it is observed to be below the mean distance.
TABLENO:6-DISTANCE OF THE BT FROM ITS ORIGIN TO MIDLINE(mm)
S.
No
Number of cadavers
Maximum distance of the BT from midline
(mm)
Minimum distance of the BT from midline
(mm)
Mean distance of the BT from midline (mm)
1. 50 13 3 8
CHART NO:6-DISTANCE OF BT FROM ITS ORIGIN TO MIDLINE(mm)
13
3
8
0 2 4 6 8 10 12 14
Maximum distance Minimum distance Mean distance
DISTANCE (mm)
FIG NO 18: DISTANCE OF THE LEFT COMMON CAROTID ARTERY FROM ITS ORIGIN TO MIDLINE
AORTIC ARCH - AA
BRACHIOCEPHALIC TRUNK - BT
LEFT COMMON CAROTID ARTERY - LCCA
LEFT SUBCLAVIAN ARTERY - LSA
46
7. DISTANCE OF THE LCCA FROM ITS ORIGIN TO MIDLINE
The distance of the LCCA at its origin to midline is measured. In the present study, the maximum distance of origin of the LCCA from midline is 24mm, the minimum distance is 11mm and the mean distance is 17mm. It is observed that in 22 cadavers (44%), the distance of the LCCA from midline is above the mean distance and in 28 cadavers (56%) it is found to be below the mean distance.
TABLE NO:7 -DISTANCE OF THE LCCA FROM ITS ORIGIN TO MIDLINE(mm)
S.
no
Number of cadavers
Maximum distance of the LCCA from
midline (mm)
Minimum distance of the LCCA from
midline (mm)
Mean distance of the LCCA from
midline (mm)
1. 50 24 11 17
CHART NO: 7- DISTANCE OF THE LCCA FROM ITS ORIGIN TO MIDLINE(mm)
0 5 10 15 20 25
Maximum distance Minimum distance Mean distance 24
11
17
DISTANCE (mm)
FIG NO :19 DISTANCE OT THE LEFT SUBCLAVIAN ARTERY FROM ITS ORIGIN TO MIDLINE
AORTIC ARCH - AA
BRACHIOCEPHALIC TRUNK - BT
LEFT COMMON CAROTID ARTERY - LCCA
LEFT SUBCLAVIAN ARTERY - LSA
47
8. DISTANCE OF THE LSA FROM ITS ORIGIN TO MIDLINE
The distance of the LSA from its origin to the midline is measured. In the present study, the maximum distance of origin of the LSA from midline is 38 mm, the mean distance is 23 mm and the mean distance is 28mm. Among the 50 cadavers dissected, in 20 cadavers (40%) the distance of the LSA from midline is above the mean distance and in 30 cadavers (60%) it is found to be below the mean distance.
TABLE NO :8- DISTANCE OF THE LSA FROM ITS ORIGIN TO MIDLINE(mm)
S.
no
Number of cadavers
Maximum distance of the
LSA from midline (mm)
Minimum distance of the
LSA from midline (mm)
Mean distance of the LSA from midline (mm)
1. 50 38 23 28
CHART NO:8 -DISTANCE OF THE LSA FROM ITS ORIGIN TO MIDLINE(mm)
38
23
28
0 5 10 15 20 25 30 35 40
Maximum distance Minimum distance Mean distance
DISTANCE (mm)
FIG NO 20: ANGLE BETWEEN THE BRACHIOCEPHALIC TRUNK AND THE AORTIC ARCH
AORTIC ARCH - AA
BRACHIOCEPHALIC TRUNK - BT
LEFT COMMON CAROTID ARTERY - LCCA
LEFT SUBCLAVIAN ARTERY - LSA
