Internal thoracic artery
Arteria thoracica interna
Also known as: internal mammary artery, LIMA, RIMA
The internal thoracic artery is a branch of the first part of the subclavian artery. It runs down about 1 cm from the edge of the sternum, behind the costal cartilages, supplying the anterior chest wall, breast and pericardium. It is the preferred graft for coronary artery bypass.
Overview
The artery leaves the underside of the first part of the subclavian artery. It descends behind the clavicle and the upper six costal cartilages, about 1 cm from the edge of the sternum. It lies in front of the endothoracic fascia and the pleura, and (lower down) in front of transversus thoracis.
In the 6th intercostal space it divides into two branches. The superior epigastric artery enters the rectus sheath and anastomoses with the inferior epigastric artery, a branch of the external iliac. This creates a link between the subclavian and external iliac arteries. The musculophrenic artery runs along the costal margin.
Anatomy
- Branches
The pericardiacophrenic artery (which runs with the phrenic nerve), thymic and mediastinal branches, the anterior intercostal arteries to spaces 1–6, perforating branches (those in spaces 2–4 supply the medial breast), the superior epigastric artery and the musculophrenic artery.
Function
- Supplies the anterior chest wall, the breast, the pericardium, the thymus, the diaphragm and the upper rectus abdominis.
Clinical significance
Coronary bypass grafting
The left internal thoracic artery is the best conduit for bypass grafting to the LAD. More than 90% of these grafts are still open after 10 years, far more than vein grafts. Its resistance to atherosclerosis is attributed to its continuous internal elastic lamina and to the high nitric oxide output of its endothelium.
Collateral pathway in coarctation
In coarctation of the aorta, blood bypasses the narrowing through the internal thoracic, epigastric and intercostal arteries. The enlarged intercostal arteries erode the undersurfaces of the ribs, which shows on X-ray as rib notching.
Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.