Carotid Bypass and Reconstruction

Direct reconstruction of the cervical carotid artery by means of a surgical bypass may be indicated in situations where revascularization via endarterectomy and primary patch closure cannot be performed. ^{[1, 2]} Examples of such clinical scenarios, in addition to primary atherosclerotic occlusion, include the following:

• Primary and secondary (traumatic or mycotic) aneurysmal degeneration of the cervical carotid artery that is not amenable to endovascular therapy
• Redo carotid operations after failed endarterectomy
• Severe long-segment radiation arteritis that is not amenable to endovascular therapy
• Malignant invasion of the carotid artery that warrants resection and reconstruction
• Revascularization before treatment of an aortic arch aneurysm via endovascular coverage of an arch vessel origin
• Infected carotid patches that call for excision and reconstruction

The morbidity of carotid bypasses is higher than that observed in primary carotid endarterectomy (CEA) with regard to rates of stroke (0.5-8%) and nerve injury (up to 10%). ^{[3, 4, 5, 6, 7, 8]} The bulk of these cases involve reoperative situations; in addition, a more extensive and difficult neck dissection is required for certain pathologic conditions involving the cervical carotid artery (ie, malignancy and radiation exposure).

Indications for carotid bypass and reconstruction are as follows:

• Long-segment atherosclerotic stenosis or occlusion
• Aneurysmal disease ^{[9, 10, 11]}
• Infection of a previously placed prosthetic carotid patch
• Malignant invasion ^[12]
• Radiation arteritis
• Recurrent stenosis after a previous endarterectomy that is not amenable to endovascular therapy ^{[13, 14]} ; a study by Spinelli et al suggested that carotid bypass may be superior to carotid angioplasty and stenting (CAS) or redo CEA for post-CEA restenosis or for intrastent restenosis after CAS for post-CEA restenosis ^[15]
• Elective debranching (revascularization) of an arch vessel in lieu of aortic arch stenting or surgery

Aortocarotid bypass has yielded good results in patients with type A acute aortic dissection complicated by carotid artery occlusion. ^[16]  

Contraindications for carotid bypass and reconstruction are as follows:

• Debilitated patient with severe comorbidities
• Lack of an appropriate distal target for revascularization (intracranial extension)
• Unaddressed inflow disease

Anatomy

The principal arteries supplying the head and neck are the two common carotid arteries (CCAs). These vessels ascend in the neck, where each divides into two branches as follows:

• External carotid artery (ECA), which supplies the exterior of the head, the face, and the greater part of the neck
• Internal carotid artery (ICA), which supplies to a great extent the parts within the cranial and orbital cavities

(See Arterial Supply Anatomy and Arteries to the Brain and Meninges.)

Procedural planning

The approach to reconstructing the carotid artery depends largely on the etiology of the disease and the anatomic level of the lesion being treated. A thorough history and a careful physical examination should be performed to assess baseline cranial nerve and functional neurologic status.

In general, if wound healing and infection are not significant concerns, a prosthetic bypass graft should be used rather than autogenous vein because restenosis rates are lower. ^[4] If wound healing issues are encountered, as in the case of infection or irradiated tissue, the need for well-vascularized muscular flaps should be anticipated to cover the reconstruction.

For reoperations, the approach is generally different from the one used for conventional CEA. The basic principle of the bypass is to place the distal anastomosis into a previously undissected and disease-free area of the CCA or the ICA, avoiding dissection of and potential injury to the cranial nerves.

Preoperative planning is essential, and characterization of the inflow vessel (eg, aorta, subclavian artery, ipsilateral CCA, contralateral CCA, vertebral artery, ^[17]  or axillary artery ^[18] ) and the distal target by means of computed tomography (CT) angiography (CTA) or magnetic resonance angiography (MRA) must be performed. Carotid angiography may be an important adjunct for preoperative assessment; however, important anatomic relations to bony and soft-tissue structures are better characterized with CTA or MRA.

Defining the extent of the reconstruction preoperatively helps the surgeon determine whether additional exposure (eg, median sternotomy and mandibular subluxation) is likely to be necessary.

Complication prevention

The following measures should be employed to help prevent complications:

• Careful preoperative assessment of cranial nerves and neurologic examination
• Thorough preoperative assessment of the inflow and target vessels, the anatomic extent of the lesion, and the lesion’s relations to surrounding structures
• Strict attention to sterile technique in the handling of prosthetic grafts
• Systemic heparinization of patients with a target activated clotting time (ACT) longer than 250 seconds before the clamping of the vessels and after the completion of graft tunneling
• Judicious use of shunts
• Preparation to assess the reconstruction at the time of the operation by means of duplex ultrasonography (US) or intraoperative arteriography

In a study aimed at determining the long-term results of prosthetic subclavian-to-carotid bypass for occlusive disease of the CCA, Illuminati et al evaluated 45 patients (mean age, 67 years; median follow-up, 58 months), of whom 38 (84%) presented with neurologic symptoms (transitory ischemic attacks [TIAs] in 29 cases and minor strokes in nine). ^[19]  The combined postoperative stroke/mortality rate was 2%, and there were no graft infections during the follow-up period. At 60 months, the overall survival rate was 71%, the rate of freedom from stroke was 98%, and the graft patency rate was 95.5%.