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Innominate Artery- A Right Brachiocephalic Artery

Innominate Artery- A Right Brachiocephalic Artery

  • The innominate artery is the largest branch of the aortic arch up to 4-5 cm long.
  • The innominate- brachiocephalic artery is the first branch of the arch.
  • It is usually a lack of branches.
  • It ends by splitting into the right common carotid artery and the right subclavian artery.

Innominate artery is another name for the right brachiocephalic artery or the brachiocephalic trunk, it is one of the largest arteries of the mediastinum that supplies blood to the upper right extremity, head, and neck. The innominate artery is the first branch of the aortic arch which is later divided into the right common carotid (which is one of the main blood supplying arteries to the head and neck) and right subclavian arteries (which supply blood to the right upper extremity). While the left common carotid artery and left subclavian artery directly come from the aortic arch.

Relationships:

  • Innominate artery posteriorly linked with the trachea, 
  • Anteriorly with left brachiocephalic vein and thymus.
  • Laterally with SVC, right brachiocephalic vein, pleura, and left common carotid artery.

Structure of Innominate – Right Brachiocephalic Artery:

The innominate artery varies greatly in size and arises from the beginning of the aortic arch anteriorly to the left carotid artery, at the level of the upper border of the 2nd right costal cartilage. 

The artery is short in length and ascends obliquely upward, backward, and to the right at the level of the upper border of the right sternoclavicular articulation, where it is bifurcated into the right common carotid artery and right subclavian artery, at the level of the sternoclavicular joint. As The brachiocephalic artery is short in length it typically crosses the trachea in front of it obliquely from left to the right, roughly at the middle of the trachea (at the level of 9th tracheal cartilage).

The right brachiocephalic artery is also in contact closely with the thymus, which typically sits superior to the artery and separates the artery from the posterior surface of the manubrium

In infants, it often splits cephalad to the sternoclavicular articulation, within the anterior triangle of the neck.

After division, the right subclavian vessel goes on to supply the entire blood to the right upper extremity as well as collateral circulation of the head through the right vertebral artery. While the right common carotid artery splits into the external carotid and internal carotid arteries, which provide a large range of the blood supply to the head and neck.

Branches of Right Brachiocephalic Artery:

The innominate- brachiocephalic artery usually gives no branches, but a small branch of the thyroid ima artery arises from it. Sometimes, it gives off a thymic or bronchial branch to compensate for deficiency or absence of one of the other thyroid vessels.

Innominate Artery- A Right Brachiocephalic Artery 2 - Daily Medicos

Embryology:

The starting portion of the aortic arch derives from a structure called the aortic sac, which is chronologically the first portion of the aorta that appears as a dilation superior to the truncus arteriosus.  This aortic sac then gives rise to two horns;

  1. The Left Horn, which combines with the stem of the aortic sac to form the proximal aortic arch.
  2. The Right Horn, which gives rise to the innominate artery.

The right horn of the aortic sac or the innominate artery fuses with the right-sided 3rd and 4th aortic arches, which give rise to the right common carotid artery and the right subclavian artery respectively.

Nerves:

The vagus nerve, and it branches the right recurrent laryngeal nerve, pass closely to the innominate artery.  The vagus nerve runs directly anterior to the division of the innominate artery, on the other hand, the right recurrent laryngeal doubles back posterior to the division and passes anteriorly to the larynx.

 Physiological Variance:

The complex embryology of the aortic arch and the great vessels with numerous natural variations is the great interest in clinical perspective. The most common aortic arch branching design variant is known as a bovine arch.  

This bovine arch variant is when both the right and the left carotid artery, along with the right subclavian artery share a common trunk, dominantly making the innominate artery have three branches instead of two. This bovine arch variation is found in approximately up to 14% of the whole world population, and findings may suggest that this variation is higher than average in those of African than Asian descent.

Other embryological variances involve:

  • Common carotid artery – The innominate- brachiocephalic artery constructively does not exist with a right subclavian artery followed by a common branch of both carotid arteries.
  • Aberrant right subclavian – The rising of right subclavian artery branches from the left side of the aortic arch or is the descending aorta. This variation can exist with or without a common carotid branch.
  • Right-sided arch – in which an aortic arch goes from left to right, showing a mirrored pattern image to the normal variation with the innominate artery gives rise to the left subclavian and the left common carotid or a divergent left subclavian.
  • Left and right separate innominate arteries
  • Four individual branches with no innominate artery
  • Double aortic arch
  • Left-sided arch with a left-sided innominate artery
  • Divergent right subclavian
  • Having a common trunk of the innominate left common carotid, and left subclavian.

Complications of Innominate- Brachiocephalic Artery:

Due to its physiological and anatomical variance here are some complications;

  • Innominate artery fistula
  • Innominate artery injury, rupture, or lesion associated with tracheostomy or trauma
  • Innominate- brachiocephalic aneurysms
  • Innominate artery stenosis

What Are The Surgical Considerations of Right Innominate Arteries?

Innominate Artery- A Right Brachiocephalic Artery 3 - Daily Medicos

Due to its great vessel, anatomic variations and prominence could be problematic in the superior thoracic cavity procedures. The innominate –brachiocephalic artery should always be taken into attention when operating inside the thoracic cavity, especially for the superior mediastinum procedure. 

  •  Because of its typical anatomy, it usually requires full exposure for median sternotomy.  
  • When operating on or close to the innominate artery, the vagus and right recurrent laryngeal nerves should be identified before, due to their proximity to the artery.
  • The anatomical innominate artery’s position is directly anterior to the trachea, which makes it vulnerable to injury when performing a tracheostomy. This potential danger of injury can be from direct puncture of the artery during the operation, as well as abrasion of the vessel from prolonged contact with the tubing
  • Prolong contact with tubing can lead to the formation of a tracheoesophageal fistula. The risk of the fistula is much greater in the lower tracheostomy site.
  • The abnormal variance of the aortic arch and great vessels can cause tracheal and/or esophageal compression.

In aortic repair procedures, innominate artery cannulation has become a highly used method for maintaining cerebral perfusion over historical time. There are no postoperative neurologic complications, and innominate artery cannulation has several benefits such as less operative time, no need for an additional incision, reduced risk of brachial plexus injury, and naked  visualization of the artery during the procedure

Conclusive Thoughts

The innominate artery or right brachiocephalic artery is the first and largest branch of the aortic arch, which is divided into the right common carotid artery (supply neck and head) and the right subclavian artery (supply right extremity). It usually has no branch but a small branch of the thyroid ima artery may be found in some people to compensate for the deficiency or absence of other thyroid vessels. Because of its great anatomic and physiological variations, it can be problematic in superior thoracic cavity procedures. So innominate arteries should always be taken into attention while operating inside the thoracic cavity.

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