The subclavian arteries provide blood supply to both upper extremities and give rise to major arterial branches, including the vertebral arteries, the internal thoracic arteries, and the costocervical and thyrocervical trunks. The internal thoracic artery is also called the left internal mammary artery (LIMA). This branch of a subclavian artery is significant in its frequent use for coronary artery bypass graft (CABG) surgery. It is often used for bypass of the left anterior descending artery of the heart, and thus, if subclavian stenosis is present in such patients, coronary insufficiency can result. It is important to know that the LIMA has an anterior take off from the subclavian artery when attempting to cannulate this vessel for ­selective angiography.

The left subclavian artery branches directly from the aortic arch, whereas the right subclavian artery arises from the brachiocephalic trunk, also known as the innominate artery (Figure 32-1). The subclavian artery courses posteriorly to the clavicle and travels between the anterior and middle scalene muscles of the lateral neck.¹

The right subclavian artery may arise directly from the aorta. A so-called “bovine” aortic arch is present in about 7% of individuals where the left carotid artery arises from the innominate artery (Figure 32-2) or shares a common trunk with the innominate artery. This term is a misnomer because this variant has no relation to the aortic arch branching pattern found in cattle. In cattle, a single great vessel originates from the aortic arch. This large brachiocephalic trunk gives rise to both subclavian arteries and a bicarotid trunk. The bicarotid trunk then bifurcates into the left common carotid artery and right common carotid artery. The vertebral artery may arise not from the subclavian artery but from the aorta itself in <1% of patients (Figure 32-3).

The term arteria lusoria refers to an aberrant right subclavian artery. The first description of this variation was provided in 1735 by Hunauld.² When an aberrant right subclavian artery variant is present, the brachiocephalic trunk is absent and 4 large arteries arise from the arch of the aorta: the right common carotid artery, the left common carotid artery, the left subclavian artery, and the final artery with the most distal left-sided origin, the right subclavian artery (Figure 32-4).

The true prevalence of subclavian artery stenosis in the general population is unknown. In the United States, estimates suggest a prevalence of 2% to 7% using clinical definitions, a number thought to underestimate its true occurrence.³ Studies in patients undergoing coronary angiography have suggested a prevalence of approximately 4%, reaching a high of 19% among patients with a history of peripheral vascular disease.^4-6 Approximately 30% to 50% of patients who require intervention for subclavian artery stenosis have concomitant coronary, carotid, or vertebral artery disease.^4,7

Subclavian stenosis is generally more prevalent among women than men. When adjusted for age and sex, it is more prevalent among African Americans and non-Hispanic whites, compared with Hispanic and Chinese individuals.⁶

The most common etiology of subclavian artery stenosis is ­atherosclerosis. Subclavian stenosis is strongly associated with traditional cardiovascular risk factors such as age, hypertension, diabetes, smoking, and high body mass index as well as markers of subclinical atherosclerosis such as increased elevated artery pulse pressure, carotid artery intima-media thickness, and ­coronary artery calcium score.⁶ Other reported causes include large artery ­vasculitis (namely Takayasu arteritis), radiation therapy, ­thoracic ­outlet ­syndrome, neurofibromatosis, and fibromuscular dysplasia.^8-12

CLINICAL FEATURES

The majority of patients with subclavian stenosis remain asymptomatic. The absence of clinical manifestations is attributed to the abundance of anastomotic vessels in the chest and neck that can maintain adequate circulation to the arm and the development of brachiocephalic collaterals in cases of slowly progressive ­stenosis.^13,14 Among those who develop symptoms, upper ­extremity claudication is one of the most common clinical manifestations associated with subclavian stenosis. Patients complain of unilateral arm pain or fatigue with exertion that is often reproducible. Pain at rest and paresthesias have also been described.^15,16

Given the arterial anatomy of the subclavian and vertebral arteries, a significant stenosis of the subclavian artery prior to the origin of the vertebral artery may cause a flow reversal in one of the vertebral arteries, resulting in the so-called subclavian steal syndrome (Figure 32-5). The subclavian steal syndrome is a functional basilar artery insufficiency that is attributed to the decrease in pressure distal to the subclavian stenosis leading to a reversed pressure gradient across the vertebral artery on the diseased side. Although significant vertebrobasilar insufficiency due to a steal phenomenon is fairly rare with isolated subclavian stenosis, patients may experience recurrent episodes of vertigo, diplopia, nausea, vision loss, and sudden generalized weakness, all of which are closely associated in time with exertion of the affected extremity.^7,16,17

A similar phenomenon, called the coronary subclavian steal ­syndrome, may be observed among patients with an internal mammary artery (IMA) bypass graft and concomitant subclavian stenosis on the ipsilateral side. If the stenosis arises proximal to the IMA graft, this shared circulation may be compromised with increased demand in the affected upper extremity, leading to angina or infarction (Figure 32-6).^18,19