Topography and irrigation [3, 4, 5]
CT scan images provided help to illustrate the zonal vascularization (figures 1 - 7), while figure 8 summarizes the irrigation of the different arteries.
Subclavian artery
The subclavian artery arises from the brachiocephalic trunk on the right, and directly from the aortic arch on the left. It exits the thorax between the anterior and middle scalene, and courses between the clavicle and the first rib, giving rise to multiples branches, described below in a proximal to distal order:
- Vertebral artery.
- Internal mammary artery: constant in origin, it arises opposite or immediately distal to the vertebral artery and courses posterior to the clavicle, internal jugular vein, innominate vein and the first rib cartilage. Then, it descends posterior to the 1st - 6th ribs and gives two branches:
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- Musculophrenic: courses posterior to the 7th - 11th ribs giving branches to the 7th - 9th intercostal spaces and breaks through the diaphragm.
- Superior epigastric: it arises at the 6th intercostal space. No chest wall irrigation from this branch.
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- Irrigation:
- Pectoralis major: 1st - 6th perforating branches.
- Breast: 2nd - 4th perforating branches.
- Skin of the anterosuperior chest wall.
- 1st - 6th intercostal spaces: perforating branches mentioned above.
- Thyrocervical trunk: originates lateral to the vertebral artery and courses medial to the anterior scalene. It gives the suprascapular artery, although this may arise directly from the subclavian, from which an acromial and a subscapular branch originate. The inferior thyroid and superficial cervical arteries also emerge from this trunk.
- Irrigation: glenohumeral joint, supraspinatus and infraspinatus through the suprascapular branch.
- Costocervical trunk: origin in posterior wall, coursing between the C7 transverse process and the 1st rib (or between C6 and C7 transverse processes). It gives two branches:
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- Supreme intercostal: may originate directly from the aorta. It courses through the 1st and 2nd intercostal spaces.
- Deep cervical.
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- Irrigation: 1st - 3rd intercostal spaces.
- Dorsal scapular artery: emerges from the superior wall and courses lateral to the middle scalene, descending posterior to the medial border of the scapula.
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- Irrigation:
- Supraspinatus.
- Infraspinatus.
- Latissimus dorsi.
Axillary artery
The axillary artery courses between the lateral margin of the first rib, proximally, and the lateral margin of the teres major tendon, distally. It gives multiples branches for the shoulder girdle and chest wall, including, proximal to distal:
- Superior thoracic artery: courses under subclavius muscle, then posterior or anteromedial to pectoralis minor, and slides between both pectoral muscles to finally emerge to the chest wall.
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- Irrigation:
- Pectoralis major and minor.
- 1st - 3rd intercostal spaces.
- Thoracoacromial artery: usually a short common trunk, following the medial border of the pectoralis minor and giving rise to four branches:
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- Pectoral: descends between both pectoral muscles.
- Acromial: courses over the coracoid process and under the deltoid, piercing it and reaching the acromion.
- Clavicular: travels up and medially reaching the sternoclavicular joint.
- Deltoid/humeral: frequently arising with the acromial branch, it courses between the pectoralis major and deltoid muscles.
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- Irrigation:
- Pectoralis major and minor.
- Deltoid: its acromial branch supplies the anterior portion of the muscle.
- Lateral thoracic artery: may arise from the subscapular branch. It courses lateral to the pectoralis minor, then posterior to the pectoralis major and emerges to the thoracic wall in the 4th and 5th intercostal spaces.
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- Irrigation:
- Pectoralis major and minor: lateral portion.
- Breast: perforating branches.
- Serratus major: main artery.
- Subscapularis.
- Subscapular artery: it emerges from the inferior margin of the subscapularis muscle, following it until the inferior scapular angle.
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- Circumflex scapular: surrounds the scapula and courses posterior.
- Thoracodorsal artery: travels lateral to the scapula between the latissimus dorsi and serratus.
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- Irrigation:
- Subscapularis.
- Serratus major: thoracodorsal branch.
- Latissimus dorsi: thoracodorsal branch.
- Intercostal spaces: thoracodorsal branch.
- Deltoid: the circumflex scapular branch supplies its posterior portion.
- Anterior humeral circumflex artery: considerably smaller than the posterior, it courses posterior to the coracobrachialis and the small head of the biceps.
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- Irrigation: glenohumeral joint.
- Posterior humeral circumflex artery: emerges at the lower margin of the subscapularis muscle and runs posteriorly through the quadrangular space.
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- Irrigation:
- Deltoid muscle: posterior portion.
- Glenohumeral joint.
The anastomotic network of subclavian and axillary arterial axis is illustrated in figure 9.
Angiographic anatomy - tips for the interventional radiologist
Angiography is the gold standard for the detection of “the bleeding vessel”. Unfortunately, most of the anatomical references mentioned are not available during this imaging approach. Therefore, the interventional radiologist must adopt a more practical view (figures 10, 11, 12, 13 and 14): caliper, the pattern of bifurcation, and the most frequent variants of each vessel and the use of MIP reconstructions of CT images, as well as angiographic runs and Cone – beam CT are helpful.
Significant variability occurs in the subclavian-axillary axis. Therefore, a fixed angiographic pattern should not always be expected. Some of the branches might be absent or have a replaced origin in another close trunk. Moreover, the compression exerted by the hematoma and the hemodynamic status of the patient may alter the acknowledged anatomy. From the angiographic point of view, both subscapular artery as the most lateral and internal thoracic / internal mammary artery as the medial edge are reliably constant, large arteries, easily recognizable to define the segment of the subclavian-axillary access to explore. The inferior border at the middle third of the clavicle is a good reference to mark the transition between subclavian and axillary artery.
The aim of embolization should be to block a demonstrated bleeding artery, but also to hypoperfuse the territory of the hematoma. Therefore, each of the involved arteries should not be seen as a close terminal compartment but a network of connecting branches and sometimes more than one artery should be embolized, combining resorbable and non-resorbable materials if considered.
As in other spontaneous hematomas related to anticoagulation, patient selection and timing to angiography and eventual embolization is sometimes difficult and lacks evidence-based parameters, being active hemorrhage on CT scan, hemodynamic instability and anemization (>4 g/dL) some of the criteria to carry the decision.
Ipsilateral radial or humeral access is probably the most convenient and saves time since catheterization of supra-aortic trunks and selective negotiation of distal branches in the subclavian-axillary axis could be difficult due to elongation or atheromatosis. Berenstein, vertebral or RIM catheters are among the most useful shapes in this context. Selective catheterization with microcatheter is recommended to avoid non target embolization and to prevent spasm and other complications. Spongostan, particles and liquid materials such as glue are among the most useful agents depending on the case (figures 15 and 16).
Key points
- The anastomotic network is profuse, existing communications between most of the subclavian and axillary branches, implying that all main branches should be interrogated on angiography and sometimes is advisable to embolize some of these communications despite not demonstrating active bleeding.
- Most relevant variants (up to 30% of cases): independent origin on the axillary artery (pectoral branch of the thoracoacromial artery), absence (superior thoracic artery) and substituted origin on a close-by artery (lateral thoracic from subscapular, superior thoracic from thoracoacromial). Therefore, a 2-3-4-axillary artery branching pattern could be found.
- Pectoral branch of the thoracoacromial artery is key supplier to pectoral muscles.