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Left internal thoracic artery

The left internal thoracic artery (LITA), historically called the left internal mammary artery (LIMA), is a branch of the subclavian artery. It arises from the inferior surface of the first part of the left subclavian artery, near its origin, and descends vertically along the inner chest wall, approximately 1–2 cm lateral to the sternum, behind the costal cartilages.

The LITA gives off several important branches: anterior intercostal arteries, perforating branches (to the breast, pectoral muscles, and overlying skin), and the pericardiacophrenic artery. It terminates at the sixth intercostal space, where it divides into the superior epigastric artery and the musculophrenic artery, which continue into the abdominal wall and diaphragm respectively.

Clinically, the LITA is the gold-standard conduit for coronary artery bypass grafting (CABG) due to its excellent long-term patency rates. It is also important in breast surgery, chest wall reconstruction, and collateral circulation in subclavian artery stenosis (via internal thoracic–epigastric collaterals).

Synonyms

  • Left internal mammary artery (LIMA)

  • Arteria thoracica interna sinistra

Function

  • Supplies blood to the anterior chest wall, sternum, breasts, pericardium, diaphragm, and anterior abdominal wall

  • Provides important collateral circulation with intercostal and epigastric arteries

  • Used surgically as a bypass graft for coronary revascularization

Branches

  • Anterior intercostal arteries (upper 6 intercostal spaces)

  • Perforating branches to chest wall and breast

  • Pericardiacophrenic artery

  • Terminal branches: musculophrenic and superior epigastric arteries

MRI Appearance

T1-weighted images:

  • Appears as a dark flow void along the posterior aspect of the anterior chest wall

  • Surrounded by hyperintense mediastinal fat, enhancing visibility

T2-weighted images:

  • Vessel lumen remains a signal void, with surrounding soft tissues showing intermediate signal

  • Helps distinguish artery from adjacent veins (which may show different flow profiles)

STIR:

  • Fat suppression accentuates the course of the artery within chest wall fat planes

  • Perivascular edema or inflammation appears bright hyperintense

T1 Fat-Saturated (Pre-contrast):

  • Lumen typically shows intermediate signal intensity, standing out against suppressed fat background

  • Useful in distinguishing artery from surrounding fat and soft tissue

T1 Fat-Saturated (Post-contrast, Gadolinium):

  • Artery enhances brightly and homogeneously, clearly outlining its course

  • Helps detect stenosis, vascular anomalies, or neoplastic involvement

MRV (Magnetic Resonance Venography/Angiography equivalent):

  • Maps the full course of the LITA from the subclavian artery to its terminal branches

  • Excellent for CABG planning, vascular anomalies, and chest wall vascular lesions

CT Appearance

CT Pre-Contrast:

  • LITA appears as a small tubular soft-tissue density along the posterior sternum

  • Calcifications in older patients or atherosclerosis may be visible

CT Post-Contrast:

  • Enhances brightly as it runs along the sternum to the sixth intercostal space

  • Outlines branches including anterior intercostal arteries and perforators

CTV (CT Venography/Angiography):

  • High-resolution 3D reconstructions map the origin, course, branching pattern, and terminal bifurcation

  • Gold standard for pre-surgical mapping of LITA for CABG or reconstructive procedures

  • Detects stenosis, aneurysm, or collateral circulation pathways

CT image

internal thoracic artery left