There are two forms of carotid–carotid bypass: ipsilateral common carotid to internal carotid artery (ICA) interposition bypass and common carotid to common carotid crossover bypass. They are infrequently performed but the requisite skills are well within the province of any experienced vascular surgeon. In truth, neither type of bypass has ever been commonly indicated but many patients who previously may have been candidates (e.g., patients with symptomatic innominate artery occlusions or irradiated carotid bifurcations) now have stents placed.

Ipsilateral common carotid to ICA bypass graft, in our practice, is often a “bail-out” or emergent procedure in difficult elective “atherosclerotic” cases or when complications arise. Less commonly it is a planned elective procedure.

We favor the eversion technique for all patients undergoing elective carotid endarterectomy (CEA). In this, the ICA is divided from its origin and its wall is peeled off the plaque. The common carotid artery (CCA) and proximal external carotid artery (ECA) are next cleared of atheroma and finally the ICA is reanastomosed to its origin. As with conventional endarterectomy, the surgeon must identify a good “end-point” where the plaque ends and the intima becomes normal. This is readily accomplished in most patients but rarely (less than 1% of operations), the plaque is continuous with the intima and a clear end-point cannot be demarcated. In this instance, we transect the internal carotid distally and perform an interposition graft from the endarterectomized CCA to the distal ICA in an end-to-end fashion, usually using a 6-mm-diameter prosthetic graft. Such difficulties can also be encountered during “conventional” CEA when an unsatisfactory end-point is identified. In both “conventional” and eversion techniques, iatrogenic injuries may occur such as perforation or excessive thinning of the ICA wall. Some centers perform routine completion angiograms after CEA and large intimal flaps will mandate bypass.

When patients sustain an immediate postoperative arterial thrombosis following elective CEA, we reexplore them emergently. If the ICA is thrombosed, we excise all endarterectomized ICA due to its assumed thrombogenicity and replace it with a prosthetic or vein graft.

Carotid wall infection is rare, especially when using the eversion technique which eschews use of prosthetic material, but not unknown. It usually arises from an infected hematoma and presents as a pseudoaneurysm or secondary hemorrhage. In conventional CEA, where patching is standard of care, an infected prosthetic patch is the cause. In
both instances, a vein graft is used following excision of all grossly infected native artery. The final, rare emergent indication is penetrating trauma.

The commonest nonemergent indication is carotid artery restenosis following CEA. Although surgery (either redo CEA or bypass) has been supplanted by stenting, it still has a role in some patients—and, of course, in the management of in-stent restenosis (see Fig. 5.1). The second indication for bypass is patients with radiation arteritis. Atherosclerotic carotid artery aneurysms and extensive carotid body tumors (Shamblin types II and III) are the final elective indications.

Common carotid to common carotid crossover bypass was previously indicated for patients with occlusive proximal common carotid disease not amenable to subclavian-carotid bypass and not fit enough for or desirous of an ascending aorta to carotid bypass. The majority of these patients in most series (including our own) had symptomatic CCA stenoses. On rare occasion, it was performed for asymptomatic stenoses. Many of these open surgical operations have been supplanted by endovascular procedures. Ironically, endovascular therapy has generated a new indication for this operation. Stenting is now the treatment of choice for thoracic aortic aneurysms. Aortic arch “debranching,” by increasing the proximal “landing zone” for stent grafts allows more patients access to thoracic endovascular aneurysm repair (TEVAR). Debranching requires at least left common carotid to left subclavian artery bypass, but, on occasion, right CCA to left common carotid bypass as well. This permits the stent graft to lie across the origins of the left subclavian and left common carotid arteries. The last indications for carotid crossover bypass are giant cell arteritis and Takayasu’s arteritis affecting the proximal supra-aortic trunks and proximal innominate artery atherosclerosis causing severe right arm ischemia.

For patients undergoing either carotid bypass, assessment of benefit is key. This starts with a comprehensive history and physical examination. Cardiology evaluation is a prerequisite in most centers in the United States. In our center, at least, routine otorhinolaryngologic consultation is not obtained, even in patients who have already had contralateral carotid surgery. For all patients with suspected carotid disease, Duplex scanning is used to evaluate the extracranial carotid, subclavian, and vertebral arteries. It is rapid, noninvasive and highly sensitive and specific when performed by an experienced vascular technologist. The main limitation of carotid Duplex, however, is an inability to visualize the intrathoracic or intracranial vessels. We, therefore, often supplement Duplex with computerized tomographic angiography (CTA) to obtain a fuller picture of these arteries (see Fig. 5.1). Magnetic resonance angiography (MRA) still is used but its longer imaging times relative to CTA and lack of applicability in patients with impaired renal function has reduced its role. Catheter angiograms are reserved for those patients where there is a discrepancy between CTA and Duplex. It is more invasive than either, but is still regarded as the “gold standard” for evaluation the aortic arch and supra-aortic trunks. Given the potentially devastating consequences of carotid artery surgery, careful counseling of all patients is essential. The risk of minor and major stroke as well as the repercussions of cranial nerve damage must be explained to the patient and documented. In patients for whom vein will be needed for bypass, Duplex vein mapping and marking of the legs is performed.

On the morning of surgery, all patients have a complete blood count, basic metabolic panel and are typed and screened. They receive a prophylactic dose of intravenous antibiotics within 1 hour of skin incision, usually a first-generation cephalosporin such as cefazolin in patients who are not allergic to beta-lactams. For allergic patients, we use a weight-based dose of vancomycin. We do not routinely stop any antiplatelet agents but will stop warfarin or the newer oral antithrombin agents.