Supreme intercostal arteries

Last revised by Daniel MacManus on 13 Mar 2021

The supreme intercostal arteries, or superior intercostal arteries, are formed as a direct result of the embryological development of the intersegmental arteries. These arteries are paired structures of the upper thorax which normally form to provide blood flow to the first and second posterior intercostal arteries.

The supreme intercostal artery is traditionally thought to form as an anastomosis between the 8th and 9th intersegmental artery branches and the ipsilateral subclavian artery 1. In a variation of nomenclature, new research suggests that the supreme intercostal artery is actually derived from the 7th and 8th intersegmental arteries although it remains that it is formed by the two intersegmental arteries caudal to the subclavian formation 2. After the involution of the portions of the intersegmental arteries between the aorta and the anastomosis, the supreme intercostal artery serves as the principal source for arterial blood flow to the posterior intercostal arteries of the 1st and 2nd ribs. 

The supreme intercostal artery, as the first branch off of the costocervical trunk, normally courses inferiorly and posteriorly from its origin along the medial and posterior aspect of the thorax.  It crosses the neck of the first rib anteriorly prior to giving off two branches which form the first and second posterior intercostal arteries.  These arterial branches supply the intercostal tissues of the first and second ribs in the same fashion as the lower intercostal arteries 2.

There is noted variation of the supreme intercostal artery in both its origin as well as its distribution. Usually originating from the costocervical trunk, the supreme intercostal artery also may arise from the thyrocervical trunk or its subsequent branches, such as the dorsal scapular artery or inferior thyroid artery. Additional origins may arise from the axillary artery, second intercostal artery, or the vertebral artery where it will pass through the transverse foramen of the 7th cervical vertebra and then course inferiorly and pass posterior to the ribs. There have been cases documented of the left supreme intercostal artery originating from the internal thoracic artery or as a fourth branch off the aortic arch 3.

Distribution varies from the expected region of the first and second intercostal spaces which occurs in approximately 72% of cases to involve the 2nd and 3rd spaces in approximately 8% of cases, while approximately 20% involve only the first intercostal space. Some researchers have suggested that the anatomically normal course of the supreme intercostal artery may only involve the 1st intercostal space 2. In cases where only the first intercostal space is supplied, the artery is diminutive when compared to arteries feeding both the 1st and 2nd spaces 3.

Clinical significance is limited, although in cases of arterial bleeding from the first or second intercostal arteries occurs, it is helpful for the interventional radiologist to know the origin of these vessels as well as their variants.

Additionally, the supreme intercostal arteries serve as a major source of collateral blood flow to the distal aorta in cases of coarctation, frequently from the bilateral supreme intercostal arteries 4 .

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