Internal thoracic artery

At a glance

English

Internal thoracic artery

Latin (TA2)

Arteria thoracica interna

System

Artery

Region

Trunk

Side

Paired, left and right

About the internal thoracic artery

The internal thoracic artery, which surgeons still often call the internal mammary artery, leaves the under surface of the first part of the subclavian artery, opposite the thyrocervical trunk. It enters the thorax behind the clavicle and the first costal cartilage and then runs straight down on the inner face of the front chest wall, about a centimetre from the edge of the sternum. Its distance from the bone is smallest at the first intercostal space and widens slightly lower down. A pair of internal thoracic veins travels with it.

Along most of its course it lies behind the costal cartilages and the internal intercostal muscles and in front of the pleura; lower down transversus thoracis separates it from the pleura. In the upper chest the phrenic nerve crosses it. At about the sixth intercostal space it ends by dividing into the musculophrenic artery, which runs along the costal margin, and the superior epigastric artery, which continues its line into the rectus sheath.

On the way it gives a series of branches. Small mediastinal and thymic twigs go to the front of the mediastinum, and the pericardiacophrenic artery accompanies the phrenic nerve to the pericardium and diaphragm. Sternal branches feed the sternum and transversus thoracis, and perforating branches pass forwards through the upper intercostal spaces to the overlying muscle and skin. In each of the upper six spaces it gives a pair of anterior intercostal arteries, which run laterally and join the posterior intercostal artery and its collateral branch.

Its main clinical use is in coronary bypass surgery. The left internal thoracic artery, joined to the anterior interventricular (left anterior descending) branch, stays open for longer than vein grafts and most other arterial grafts, and it is the conduit surgeons prefer. Through its links with the inferior epigastric and intercostal arteries it also forms a collateral path around a coarctation of the aorta.

Course and supply

Arises from

Arises from the under surface of the first part of the subclavian artery, opposite the thyrocervical trunk.

Ends in

Ends at about the sixth intercostal space by dividing into the musculophrenic and superior epigastric arteries.

Supplies

Supplies the anterior chest wall, sternum, upper intercostal spaces, anterior mediastinum, thymus, pericardium and diaphragm, and through its terminal branches the upper anterior abdominal wall.