Primer in Cerebrovascular Disease: Innominate and Subclavian Disease

Introduction

Diseases of the subclavian and innominate artery are rare entities that impact less than 5% of the population. Limited data are available to describe their prevalence and natural history, and current knowledge is derived predominantly from case reports and small case series.

Evaluation and Workup

Diseases involving the subclavian and innominate arteries are largely asymptomatic and discovered incidentally on radiographic imaging performed for other reasons. Any patient suspected of, or diagnosed with, subclavian or innominate disease, should undergo a complete history and physical examination including a thorough cardiac, neurological, and vascular evaluation. Vascular examination should include bilateral upper extremity pulses, individual upper extremity blood pressure measurements, auscultation for bruits, evaluation for pulsatile masses, documentation of upper extremity claudication or rest pain, and evidence of upper extremity embolization. A thorough neurological examination should evaluate both anterior and posterior circulation. Finally, patients should be examined for symptoms of compression of the central structures surrounding the aortic arch as well as more distal subclavian arteries. These symptoms may include nerve palsy resulting from compression of the brachial plexus, hoarseness from compression of the recurrent laryngeal nerve, and tracheal compression/deviation.

Imaging of the aortic arch has evolved rapidly since mid-1990s. Historically, aortography was considered the gold standard for diagnosis of brachiocephalic disease; however, it has been replaced by computerized tomography (CT) and magnetic resonance (MR) angiography both for the purpose of diagnosis and operative planning. CT or MR of the brain should also be performed before any planned revascularization. Presence of recent infarcts may affect the timing of an intervention due to the associated risk of reperfusion injury. Knowledge of the circle of Willis patency along with concomitant carotid bifurcation disease can aid in operative planning. Duplex ultrasound can provide indirect evidence of proximal subclavian or innominate stenosis, such as reversal of flow in vertebral arteries, or reduced flow velocities in right common carotid and subclavian arteries. However, its value can be limited due to overlying bony structures.

Prior to intervention, a thorough preoperative risk assessment is necessary for all patients. The incidence of concomitant coronary atherosclerosis approaches 40% , and cardiac evaluation is recommended particularly if open surgery is being considered. This assessment should comprise of a transthoracic echocardiogram and 12-lead electrocardiogram. Patients with a low ejection fraction (<50%) or ischemic changes on their electrocardiogram should be referred for additional workup with a stress test or coronary angiography.

Subclavian and Innominate Stenosis