Carotid Subclavian Bypass/Transposition and Vertebral Transposition

Introduction

Cervical reconstruction of arch branch vessels requires detailed understanding of neck and thoracic outlet anatomy. Revascularization of the subclavian arteries using a carotid subclavian bypass or transposition can be used to improve or preserve blood flow to the left subclavian and its branch vessels. Proximal occlusive lesions of the subclavian can be treated using these procedures avoiding open chest reconstruction and as an alternative if endovascular stenting has failed. Coronary and subclavian steal syndromes secondary to a proximal subclavian stenosis can be similarly treated. With increased use of thoracic endovascular aortic repair (TEVAR), the left subclavian artery may have to be intentionally covered to achieve an adequate proximal sealing zone in the treatment of thoracic aneurysms and dissections. This vessel can be revascularized with one of these techniques to preserve arterial perfusion to the vertebral artery and upper extremity and decrease the risk of spinal cord ischemia. A right-sided operation can also be performed to revascularize an aberrant right subclavian artery.

Surgical Planning

Decision making regarding the use of a carotid subclavian bypass versus transposition is based on clinical situation, anatomy, and surgeon experience/comfort. An absolute contraindication for a subclavian-to-carotid transposition is a patent left internal thoracic artery (ITA) to left anterior descending coronary artery bypass graft. In this situation, a carotid subclavian bypass is performed to maintain perfusion to the coronary artery bypass graft while the subclavian artery is clamped distal to the ITA. A very proximal vertebral artery may prohibit transposition of the subclavian. Other relative reasons to consider a bypass over a transposition are large arch aneurysms that displace the left subclavian artery and may make the dissection and mobilization challenging as well as presence of dominant vertebral artery.

In the setting of TEVAR, a benefit of a transposition as opposed to a bypass is that an additional procedure to embolize or occlude the origin of the subclavian is not necessary as the proximal subclavian artery is ligated during a transposition. For an elective TEVAR, current guidelines recommend routine preoperative revascularization; however, these recommendations are based on very low–quality evidence.

Preparation

To perform these procedures the patient is placed in the supine position with the head at the top of the operating table and with the neck extended and rotated toward the contralateral side. This can be facilitated with the use of a shoulder roll and positioning the bed in semi-Fowler, or “beach-chair,” position.