Internal thoracic artery
Branch of the subclavian artery that descends just lateral to the sternum. It supplies the anterior chest wall and breast and is the preferred conduit for coronary bypass (LIMA to LAD).
Core anatomy
- Location
Deep surface of the anterior thoracic wall, about 1 cm lateral to the sternal border, behind the costal cartilages.
- Origin
Inferior surface of the first part of the subclavian artery.
- Course
Descends behind the clavicle and the upper six costal cartilages, anterior to the pleura (and, lower down, to transversus thoracis), about 1 cm lateral to the sternum.
- Branches
- Pericardiacophrenic artery (accompanies the phrenic nerve)
- Anterior intercostal arteries (spaces 1–6)
- Perforating branches (including medial mammary branches to the breast)
- Thymic and mediastinal branches
- Terminal branches at the 6th intercostal space: the superior epigastric artery (continues into the rectus sheath) and the musculophrenic artery
- Supplies
Anterior thoracic wall, breast, thymus, pericardium, diaphragm, and (via the superior epigastric) the upper anterior abdominal wall.
- Anastomoses
With the posterior intercostal arteries (from the aorta) via the anterior intercostals. With the inferior epigastric artery (external iliac) via the superior epigastric artery in the rectus sheath, a route for collateral flow between the subclavian and iliac systems.
- Termination
Divides at about the 6th intercostal space into the superior epigastric and musculophrenic arteries.
Structures supplied
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Clinical correlations
Coronary artery bypass grafting (CABG) PANCE
- Mechanism / lesion
The left internal thoracic (mammary) artery (LIMA) is usually left attached to the subclavian artery and anastomosed to the anterior interventricular artery (LAD).
- Classic presentation
The LIMA-to-LAD graft has the best long-term patency of any bypass conduit, better than saphenous vein grafts.
Collateral pathway in coarctation of the aorta PANCE
- Mechanism / lesion
With narrowing of the aorta beyond the left subclavian artery, blood flows subclavian → internal thoracic → anterior intercostals → posterior intercostals → descending aorta (and via the superior and inferior epigastrics).
- Classic presentation
Enlarged, tortuous intercostal arteries cause rib notching. Pulsatile collaterals may be felt in the intercostal spaces or around the scapula.
Injury in parasternal procedures or trauma
- Mechanism / lesion
Penetrating trauma near the sternum, or needles placed parasternally (e.g. a parasternal pericardiocentesis approach).
- Classic presentation
Hemothorax or anterior mediastinal hematoma. Procedures stay away from the immediate parasternal line, or use ultrasound guidance.
High-yield PANCE pearls
- LIMA → LAD is the gold-standard CABG graft (best long-term patency).
- Coarctation: internal thoracic → intercostal collaterals → rib notching.
- Terminal branches: superior epigastric + musculophrenic (6th intercostal space).
Imaging anatomy
- CT
CT angiography assesses graft patency after CABG and shows enlarged collaterals in coarctation. The vessels are visible just behind the costal cartilages on contrast CT.
- Ultrasound
Parasternal Doppler can identify the vessel before procedures; also used to assess its suitability as a graft. verify
- Key views & landmarks
- Coronary CT angiography or invasive angiography for graft patency
Physical exam
- Surface landmarks
Runs about 1 cm lateral to the sternal border, deep to the costal cartilages. Not palpable.
- Strength / function testing
In suspected coarctation, compare upper and lower limb blood pressures and palpate for radiofemoral delay.
Self-quiz
During CABG, which conduit is preferentially anastomosed to the left anterior descending artery for the best long-term patency?
Correct answer: C
The left internal thoracic (mammary) artery to the LAD has the best long-term patency and survival benefit of the bypass conduits.
Show answer
C
The left internal thoracic (mammary) artery to the LAD has the best long-term patency and survival benefit of the bypass conduits.
The internal thoracic artery arises from which vessel?
Correct answer: B
The internal thoracic artery arises from the inferior surface of the first part of the subclavian artery, opposite the thyrocervical trunk.
Show answer
B
The internal thoracic artery arises from the inferior surface of the first part of the subclavian artery, opposite the thyrocervical trunk.
In coarctation of the aorta, dilated collateral vessels erode the ribs. Through which main pathway does blood reach the descending aorta?
Correct answer: B
Blood flows from the subclavian into the internal thoracic artery, through the anterior intercostal arteries into the posterior intercostals, and back into the descending aorta beyond the coarctation.
Show answer
B
Blood flows from the subclavian into the internal thoracic artery, through the anterior intercostal arteries into the posterior intercostals, and back into the descending aorta beyond the coarctation.
At the 6th intercostal space, the internal thoracic artery divides into which two terminal branches?
Correct answer: A
The internal thoracic artery ends at about the 6th intercostal space by dividing into the superior epigastric (into the rectus sheath) and musculophrenic arteries.
Show answer
A
The internal thoracic artery ends at about the 6th intercostal space by dividing into the superior epigastric (into the rectus sheath) and musculophrenic arteries.
In the rectus sheath, the superior epigastric artery anastomoses with which artery?
Correct answer: E
The superior epigastric (from the internal thoracic) anastomoses with the inferior epigastric (from the external iliac) in the rectus sheath, a collateral route between the subclavian and iliac systems that enlarges in coarctation of the aorta.
Show answer
E
The superior epigastric (from the internal thoracic) anastomoses with the inferior epigastric (from the external iliac) in the rectus sheath, a collateral route between the subclavian and iliac systems that enlarges in coarctation of the aorta.