Internal Thoracic Artery

arteria thoracica interna

The internal thoracic artery (internal mammary artery, IMA) arises from the inferior surface of the subclavian artery and descends on the inner surface of the anterior thoracic wall, lateral to the sternum, between the costal cartilages and transversus thoracis muscle. It gives off anterior intercostal branches, the pericardiacophrenic artery, and terminates at the sixth intercostal space by dividing into the musculophrenic and superior epigastric arteries.

Region: Chest

Clinical Relevance

Clinical Notes

The left internal thoracic artery is the gold standard conduit for coronary artery bypass grafting, anastomosed to the left anterior descending artery with 10-year patency rates exceeding 90%, far superior to vein grafts. Bilateral IMA harvesting is increasingly used in younger patients for total arterial revascularisation. The artery is also used in reconstructive surgery as a pedicled or free flap. It must be identified and protected during thoracic port insertion, chest drain placement, and parasternal thoracotomy approaches.

Pathology

Common Injuries & Conditions

IMA Injury in Chest Drain Insertion

Intercostal chest drain insertion too close to the sternum risks laceration of the internal thoracic artery, causing massive haemothorax requiring emergency thoracotomy for control; drains should always be placed lateral to the midclavicular line to avoid this vessel.

IMA Graft Occlusion

Despite superior long-term patency compared to saphenous vein, IMA grafts can develop competitive flow failure when the native coronary stenosis is mild, or late atherosclerosis after decades, requiring repeat revascularisation.