Carotid Subclavian Reconstructions
Mark D. Morasch
Indications/ContraindicationsTreatment for occlusive lesions involving the proximal subclavian artery is indicated in patients with posterior brain circulation or ipsilateral arm ischemia and in patients with coronary artery steal after the use of an internal mammary artery in coronary artery bypass grafting. Patients with subclavian steal syndrome, which results when blockage in the first portion of the subclavian artery causes pressure distally to drop below that at the vertebrobasilar junction, present with posterior cerebrovascular symptoms as blood is siphoned away from the basilar artery. Less commonly, myocardial ischemia can occur as a result of coronary steal which can develop in patients with subclavian disease proximal to an internal mammary revascularization of the coronary arteries. Patients may also develop varying degrees of arm ischemia ranging from the claudication observed in patients with subclavian steal to limb-threatening ischemia resulting from extensive arterial occlusion or emboli. Asymptomatic occlusive lesions in the proximal subclavian artery should be considered for repair in patients contemplating myocardial revascularization via an internal mammary artery and in patients with bilateral subclavian artery disease in order to permit and facilitate blood pressure management. Truly asymptomatic lesions of the proximal subclavian artery, without alternative indications for repair, should be observed.
With the advent of thoracic endovascular therapy, surgical manipulation of the supra-aortic trunks to prepare patients with thoracic and thoracoabdominal aortic aneurysms, dissections, or traumatic tears for an endovascular stent-graft repair has become accepted. Subclavian artery reconstruction is performed in this circumstance to preserve vertebral and left upper extremity flow while extending the proximal neck “landing zone” prior to endograft deployment. Not only is preservation of the vertebral artery critical, but it is equally important to mobilize and preserve the valuable internal mammary artery. In contradistinction to carotid-subclavian bypass, a subclavian transposition not only preserves arm, vertebral and mammary flow, it obviates the need for proximal subclavian ligation or transcatheter embolization of the vessel to prevent the development and persistence of a large retrograde Type II endoleak.
Rarely, patients with developmental anomalies involving the arch vessels require subclavian artery reconstruction to treat symptoms arising from esophageal or tracheal compression from a normal or aneurysmal aberrant retroesophageal right subclavian
artery (ARRSA). Only ARRSA that are symptomatic, or have undergone significant aneurysmal degeneration, should be considered for repair.
artery (ARRSA). Only ARRSA that are symptomatic, or have undergone significant aneurysmal degeneration, should be considered for repair.
Preoperative Planning
Arch duplex ultrasound is utilized in some centers as a screening tool, but ultrasound can be difficult to interpret as insonation through the bony structures of the mediastinum requires the skills of an experienced technologist. Once a diagnosis has been established, multiplanar views of the aortic arch utilizing digital subtraction angiography are still considered to be the best tool for planning revascularization. A complete arch and four-vessel study should be performed with specific emphasis placed upon the vessel’s origins and late views to show vascular reconstitution from steal. Magnetic resonance and CT angiography are less-invasive modalities that are being used more frequently as the primary imaging modality.
Risk assessment and preoperative cardiac evaluation should follow guidelines similar to those for carotid bifurcation surgery. Patients may be considered at higher risk if there is history of significant cardiorespiratory disease or prolonged steroid use, the inability to hyperextend their necks or arteritis from prior radiation therapy. These patients may be considered for endolumenal therapeutic options.
SurgeryPositioning
Both subclavian transposition and carotid-subclavian bypass are completed with patients in supine, semi-Fowler’s position. The head is turned away from the operative site and the table tilted slightly to the opposite side. The operator may stand on either side of the patient, but may find the dissection of the subclavian artery during transposition to be facilitated by standing on the side opposite the surgical incision.
Subclavian to Carotid Transposition
Cervical reconstruction via transposition is the surgical technique of choice for single proximal occlusive lesions involving the subclavian arteries. Subclavian transposition is completed through a short, transverse cervical incision above the clavicle. The exposure is carried out between the two heads of the sternocleidomastoid muscle. This is an important contradistinction to carotid-subclavian bypass which is carried out lateral to the entire sternocleidomastoid muscle (Fig. 3.1). After dividing the omohyoid muscle between ligatures or with electrocautery, the jugular vein is reflected laterally and the common carotid is reflected medially with the vagus nerve. The carotid is mobilized circumferentially with the dissection carried out deeply toward the mediastinum. On the left side, the thoracic duct and small identifiable lymphatic vessels are identified, ligated, and divided (Fig. 3.2
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