A Study of Variations in Origin, Length, Course and
dissected. The ribs were cut about 5cms away from costochondral junction on both sides first down to 8th ribs. The anterior thoracic wall was lifted from above downwards gradually separating from the underlying structures. Finally, a cut is made across, joining the lower ends of the two vertical cuts of right and left sides to free the anterior thoracic wall with internal thoracic artery of both sides6. The specimens were washed with water to get rid of clots and connective tissue and preserved with 10% formalin.1:10 thin solution of fevibond in acetone was prepared, arteries were painted afterwards colored with red oil color, and specimens were allowed to dry.
Following statistical methods were applied in the present study,
1. Cross tabs procedure (Contingency coefficient test) 2. Chi-square test
3. Descriptive statistics 4. Independent samples 't' test
All the statistical operations were done through SPSS for Windows (version 14.0-Evaluation version), SPSS Inc. New York.
Fig. 1 and 2: Measurement of the Total Length of the Artery.
RESULTS
Table 1. ITA specimens grouped according to their pattern of origin and their percentage.
S. TYPE SIDE TOTAL % GRAND Total
No TOTAL %
1 Normal origin from Right 22 44
the first part of 42 84
Subclavian artery Left 20 40
2 Arising with Right 02 04
Thyrocervical 05 10
trunk Left 03 06
3 Arising with Right 01 02
Suprascapular 01 02
artery Left NIL --
4 Arising with Right NIL --
Suprascapular artery 02 04
and Transverse
cervical artery Left 02 04
Table 2. ITA specimens grouped according to their termination in the intercostal spaces
S. Termination SIDE TOTAL % GRAND Total
No TOTAL %
1 Right 21 42
6th ICS 44 88
Left 23 46
2. Right 03 06
5th ICS 05 10
Left 02 04
3. Right 01 02
4th ICS 01 02
Left NIL -
Chi-Square ( ) = 67.72, P < 0.000 (highly significant).
Table 3. Mean Length of Internal Thoracic artery in male (in cm).
Male
Right Left
Mean Length 18.00 Mean Length 18.29
Std. Deviation 0.3408 Std. Deviation 0.3331 Table No.4: Mean Length of Internal Thoracic artery in
female (in cm).
Female
Right Left
Mean Length 18.05 Mean Length 18.36
Std. Deviation 0.3954 Std. Deviation 0.2123
Graph 1: Pie chart showing variations in the pattern of origin of ITA specimens (%).
26 Prakash KG 106-109.pmd 107 8/27/2012, 6:39 PM
DISCUSSION
The study of Internal Thoracic Artery has gained its utmost importance in cardiac surgeries and it is most commonly used graft in CABG. Bypass surgeries are done to bypass the occluded or nearly occluded coronary arterial segments, to relieve ischemic symptoms, persistent angina or congestive heart failure from severe occlusive diseases of the coronary arteries.
A total of 50 specimens of internal thoracic arteries were studied by dissection method to know the possible variations pertaining to its origin, length, course, branches, termination and inner luminal diameter at origin, 2nd ICS, 4th ICS & 6th ICS, to help the cardiac surgeons to choose the level for bypass surgeries, to assist the plastic surgeons in the post mastectomy microvascular breast reconstruction surgeries, wherein perforating branches of the artery are the recipient vessels and to give the information to the radiologists to have sound knowledge about the possible anatomical variations of the artery that they can come across during radiological investigations.
According to Daseler E.H. and Anson B. J., the origin of the artery is variable1.
Based on a study of 769 dissected specimens, it has been observed that the internal thoracic artery took origin as follows
A. From the first part of Subclavian artery (609 of 769, 79.19%; Rt-324, Lt- 285).
B. From common stem with thyrocervical trunk (68 of 769 extremities; 8.84%; Rt-11, Lt-57).
C. From common trunk with suprascapular artery (29 of 769 extremities, 3.77%; Rt-9, Lt-20).
D. As a direct branch of second part of subclavian artery (28 of 769 extremities, 3.64%; Rt- 6, Lt-22).
E. From common trunk with inferior thyroid artery (9 of 769 sides, 1.17%; Rt-5, Lt-4).
F. From direct common trunk with transverse cervical artery (6 of 769 sides, 0.78%; Rt-2, Lt-4).
G. As direct branch from 3rd part of subclavian artery (6 of 769 sides, 0.78%; Rt-4, Lt- 2).
H. From common trunk with superior intercostal artery (6 of 769 sides, 0.78%; Rt-4, Lt-2).
I. As direct branch of axillary artery (4 of 769 sides, 0.52%; Rt- 2, Lt-2).
J. Internal thoracic, transverse cervical, suprascapular arteries, all from common trunk (2 of 769 extremities, 0.28%; Rt-1, Lt-1).
Comparison of present work with that of Daseler EH and Anson B.J1
Normal origin of the artery from first part of Subclavian artery is 84% in the present study compared with 79.19% in above workers. Similarly, the artery taking origin with Thyrocervical trunk is 10% in the present work compared to 8.84% in above anatomists study. Origin of the artery with suprascapular and transverse cervical arteries is 4% in the present study compared to 0.28% in above workers.
To determine the relationship of the Phrenic nerve to internal thoracic artery, it has been analyzed that the nerve passes from lateral to medial behind the first rib, was found to cross the artery superiorly and remains medially in 16 of 25 specimens on the left and 12 of 25 on right side, but other specimens, it crosses inferiorly. These findings were similar to the findings of Owens WA & Gladstone DJ3. And therefore, it can be concluded that there is no constant relationship between these structures.
SUMMARY
The study of Internal Thoracic Artery (ITA) has gained its utmost importance in cardiac surgeries and most commonly used graft in coronary arterial bypass surgeries (compared to other grafts like Radial artery, Saphenous vein etc). CABG procedure is done to bypass occluded or nearly occluded coronary arterial segments to relieve ischemic symptoms, persistent angina or congestive heart failure from severe occlusive diseases of the coronary arteries.
A total of 50 specimens of internal thoracic arteries were studied by dissection method to find out the possible variations pertaining to its origin, length, course, branches, termination and inner luminal diameter at origin, 2nd ICS, 4th ICS & 6th ICS, with aim to guide the cardiac surgeons to choose the level for bypass graft surgeries(CABG), to help the plastic surgeons in post mastectomy micro vascular breast reconstruction (TRAM-Transverse Rectus Abdominis Myocutaneous flap technique, wherein perforating branches of the artery are the recipient vessels)4 and
Graph 2: Graph showing ITA specimens grouped according their termination in the intercostal spaces.
use of the anatomical proximity of interanal mammary artery to the left anterior descending artery( left anterior interventricular branch) in coronary bypass graft provided to be having good results.2
• Internal thoracic artery most commonly takes origin from the first part of Subclavian artery (84%).
• There is no constant relationship between phrenic nerve and the artery at or above the first rib which emphasize the need for the caution for dissecting ITA at that level.
• Internal thoracic artery most commonly terminates in 6th ICS (88%) and mean total length being more on left side than right side by 0.30 cm.
• The mean total length of the artery on the left side is more than the right side by 0.30 cm.
REFERENCES
1. Deseler EH, Anson BJ. Surgical anatomy of the subclavian artery and its branches. Surg. Gynecol.
Obstet 1959; 108: 149-174.
2. Krittredge RD, Kemp HG. Use of internal mammary artery in coronary arterial bypass graft surgery. Am. J. Roentol 1977 March; 128(3):
395-401.
3. Ownes WA, Glandstone DJ, Heylings DJ. Relation of internal thoracic artery with Phrenic nerve.
Ann Thoracic Surgery: 1994 (Sept); 58(3); 843-844.
4. Park MC, Lee JH, Chung J, Lee SH. Use of internal mammary vessel perforator as a recipient vessel for TRAM breast reconstruction. Ann Plast Surg:
2003 (Feb); 50(2): 132-137.
5. Standring S. Grays Anatomy: Anatomical basis of clinical practice. Chest Wall: 39th edition.
Elsevier Churchil Livingstone, Edinburgh. 2005;
pp: 964-965.
6. Romanes GJ. Cunningham's manual of practical anatomy. The walls of thorax: vol: 2; 15th edition:
oxford university press. 2009: pp: 11-16.
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