Subclavian Arteries

Overview

The subclavian arteries are major paired arteries that supply blood to the upper limbs, neck, thoracic wall, spinal cord, and parts of the brain. While the main subclavian artery itself is a large vessel, it gives rise to several smaller but crucial branches that contribute to the vascular supply of nearby muscles, nerves, and bones. These smaller branches include the vertebral artery, internal thoracic artery, thyrocervical trunk, costocervical trunk, and dorsal scapular artery.

Location

Each subclavian artery originates differently:

• The right subclavian artery arises from the brachiocephalic trunk.

• The left subclavian artery arises directly from the aortic arch.

Both arteries travel laterally, passing posterior to the anterior scalene muscle, and become the axillary arteries at the lateral border of the first rib. Along their course, they give rise to smaller branches that radiate into the neck, thorax, and scapular regions.

Structure

The subclavian artery is divided into three parts based on its relation to the anterior scalene muscle:

1. First part: Medial to the anterior scalene

2. Second part: Posterior to the anterior scalene

3. Third part: Lateral to the anterior scalene, before becoming the axillary artery

Each part gives off specific branches:

• Vertebral artery (1st part): Ascends to supply the brainstem and cerebellum

• Internal thoracic artery (1st part): Runs along the inner chest wall

• Thyrocervical trunk (1st part): Gives rise to the inferior thyroid, suprascapular, and transverse cervical arteries

• Costocervical trunk (2nd part): Gives off deep cervical and supreme intercostal arteries

• Dorsal scapular artery (3rd part, or occasionally from the thyrocervical trunk)

Function

The smaller branches of the subclavian arteries serve several key roles:

• Vertebral artery: Supplies the posterior part of the brain

• Internal thoracic artery: Supplies anterior chest wall, pericardium, and diaphragm

• Thyrocervical trunk branches: Supply the thyroid gland, neck muscles, scapula, and cervical vertebrae

• Costocervical trunk: Supplies posterior intercostal spaces and deep muscles of the neck

• Dorsal scapular artery: Supplies the levator scapulae and rhomboid muscles, contributing to scapular anastomosis

Physiological Role(s)

The smaller branches of the subclavian artery contribute to:

• Cerebral perfusion: The vertebral arteries unite to form the basilar artery, which helps maintain posterior cerebral circulation

• Collateral circulation: The thyrocervical and dorsal scapular arteries are vital in forming anastomoses around the scapula and shoulder joint

• Thoracic wall and breast perfusion: The internal thoracic artery supplies the sternum, ribs, and is often used in coronary bypass surgery

• Spinal cord blood supply: Via spinal branches from vertebral and intercostal arteries

Clinical Significance

Smaller subclavian artery branches are involved in a variety of clinical conditions and surgical procedures:

• Subclavian Steal Syndrome: A proximal subclavian artery stenosis causes reversal of vertebral artery flow, resulting in dizziness, syncope, and neurologic symptoms.

• Thoracic Outlet Syndrome: Compression of subclavian artery branches by scalene muscles or cervical ribs can impair limb perfusion.

• Internal Thoracic Artery Grafting: Commonly used in coronary artery bypass graft (CABG) surgery due to its long-term patency rate.

• Vertebrobasilar Insufficiency: Inadequate blood flow in the vertebral artery affects posterior cerebral circulation.

• Trauma or Catheterization Injury: Subclavian branches can be accidentally damaged during central line placement or trauma, leading to hematoma or ischemia.

• Embolic Stroke Risk: Atherosclerosis in the vertebral artery origin may result in emboli that travel to the brainstem or cerebellum.

Imaging of subclavian artery branches is typically performed using Doppler ultrasound, CT angiography, or MR angiography. Understanding their anatomy is crucial for vascular surgery, neurology, cardiology, and interventional radiology.