Internal thoracic veins

At a glance

English

Internal thoracic veins

Latin (TA2)

Venae thoracicae internae

System

Vein

Region

Trunk

Side

Paired, left and right

About the internal thoracic veins

The internal thoracic veins, formerly called the internal mammary veins, drain the front of the chest wall. Each runs vertically just lateral to the sternum, behind the costal cartilages and in front of the pleura, alongside the internal thoracic artery. They are slender vessels, only a few millimetres across.

Each begins low on the chest wall as the upward continuation of the superior epigastric veins, which climb from the rectus sheath. In the lower spaces there are usually two companion veins, one on each side of the artery. Higher up these commonly merge into a single trunk that lies on the medial side of the artery; the point of fusion varies, and on either side the vein may stay double or split at about the second to fourth spaces. Behind the first costal cartilage the vein, or its trunk, ends by opening into the lower border of the brachiocephalic vein of its own side.

Along its course each vein takes in the anterior intercostal veins of the upper six spaces, perforating branches from the front of the chest, and small mediastinal, thymic, pericardial and pericardiacophrenic veins. The back of the intercostal spaces drains mainly to the azygos system instead. By connecting with the epigastric veins below, the internal thoracic veins form part of a route along the front of the trunk that can carry blood between the territories of the inferior and superior venae cavae when one is obstructed; flow can run in either direction.

Knowing where these vessels run matters for any procedure through the front of the chest. Needles for biopsy or drainage of pleural fluid, and incisions beside the sternum, keep clear of the line about a finger's breadth from its edge to avoid heavy bleeding. A central line misdirected into this vein can cause pleural effusion, chest wall abscess, fluid on the lungs, breathlessness and chest pain. Cardiac surgeons see the veins when they harvest the internal thoracic artery for coronary bypass.

Course and drainage

Begins at

Begin as the continuation of the superior epigastric veins at the lower end of the sternum, usually as two companion veins.

Drains into

Usually unite into one trunk and open into the inferior border of the brachiocephalic vein of the same side behind the first costal cartilage.

Drains

Drain the anterior chest wall, including the anterior intercostal spaces and mammary region, as well as small mediastinal, thymic and pericardial veins.