Carotid Bypass and Reconstruction 

Updated: Oct 31, 2018
Author: Cheong Jun Lee, MD; Chief Editor: Vincent Lopez Rowe, MD 

Overview

Background

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] 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%).[2, 3, 4, 5, 6, 7] 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

Indications for carotid bypass and reconstruction are as follows:

  • Long-segment atherosclerotic stenosis or occlusion
  • Aneurysmal disease [8, 9]
  • Infection of a previously placed prosthetic carotid patch
  • Malignant invasion
  • Radiation arteritis
  • Recurrent stenosis after a previous endarterectomy that is not amenable to endovascular therapy [10, 11] ; 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 [12]
  • Elective debranching (revascularization) of an arch vessel in lieu of aortic arch stenting or surgery

Contraindications

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

Technical Considerations

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.[3] 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 (aorta, subclavian artery, ipsilateral CCA, or contralateral CCA) 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

Outcomes

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).[13]  The combined postoperative stroke/mortality rate was 2%, and there were no graft infections during the follow-up period. was observed throughout follow-up. 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%.

 

Periprocedural Care

Equipment

Equipment used for carotid bypass and reconstruction includes the following:

  • Surgical loupes (×2.5, ×3.5)
  • Fine vascular clamps and instruments (ie, a cervical carotid endarterectomy [CEA] set), including detachable occluding clips (eg, Heifetz or Yasargil)
  • Short occluding balloons if the vessel is not amenable to clamping
  • Arterial shunts (eg, Javid or Sundt)
  • Polytetrafluoroethylene (PTFE) or other prosthetic grafts of appropriate length and caliber – Commonly, 6-mm grafts are used for the internal carotid artery (ICA) and 8-mm grafts for the common carotid artery (CCA)
  • Sternotomy set
  • Doppler ultrasonography (US) device for intraoperative assessment of blood flow

Patient Preparation

Anesthesia

Carotid bypass and reconstruction are usually performed with general anesthesia because extensive exposure of the neck and sternotomy may be necessary. If mandibular subluxation is required for high distal targets (C1 and above), nasotracheal intubation is used. It is critical to monitor intraoperative blood pressure control and oxygenation during arterial clamping. Placement of an arterial line is thus necessary. Judicious use of vasopressors or vasodilators by the anesthesia team to maintain optimal physiologic range is of paramount importance.

Monitoring of cerebral perfusion can be accomplished by measuring ICA back-pressure before clamping or by performing intraoperative electroencephalography (EEG). The authors’ practice has been to use selective shunt placement on the basis of ICA back-pressure measurements (mean arterial pressure < 40 mm Hg). In cases where the sole vessel to the brain requires clamping, high-dose propofol and burst suppression anesthesia may be useful.

Positioning

The procedure is performed with the patient supine and the neck extended. A shoulder roll is placed to assist with neck extension. The patient’s arms are tucked, and the back is raised slightly (10-20°) in a modified beach chair position, which helps reduce venous pressure. The patient’s head is turned so as to expose the side on which revascularization is required, and the endotracheal (ET) tube is positioned and taped away from that side.

If both sides require exposure (as in a carotid-to-carotid bypass), the ET tube is placed in the center and flexed away from neck. If the saphenous vein or the superficial femoral artery is required as a conduit, then the extremity from which the vessel will be procured is prepared and draped accordingly.

Monitoring & Follow-up

After the procedure, frequent neurologic assessment and maintenance of blood pressure (with appropriate treatment of hypotension or hypertension) are paramount. Drains are placed selectively for neck decompression or continued drainage of infected fluid. The operative wound is checked often. An expanding hematoma should be identified early and promptly managed in the operating room. Patients are maintained on an antiplatelet agent. Systemic anticoagulation is reserved for high-risk grafts; the risk of major bleeding is significant.

Surveillance of the reconstruction postoperatively can be effectively performed with duplex US, as is the case after CEA. Significant alterations in blood flow warrant prompt imaging with computed tomography (CT) angiography (CTA), magnetic resonance angiography (MRA), or conventional angiography to prevent graft occlusion.

 

Technique

Approach Considerations

The basic premise of carotid revascularization is the provision of appropriate intracranial blood flow from a suitable inflow source to a healthy extracranial carotid segment. In the choice of conduit, the authors generally prefer prosthetic bypasses, but autogenous vein bypasses may be used if the size of the vein is suitable. Prosthetic bypasses avoid potential gross mismatch between a reversed vein and the recipient arteries. Patency rates are excellent with prosthetic grafts (higher than 80% at 10 years).[6, 7, 14]

The morbidity of carotid revascularization stems from cranial nerve injuries, which occur at higher rates with this procedure than with standard carotid endarterectomy. Stroke rates are comparable to those seen with endarterectomy and are acceptable (0.5-8%).[3, 6, 7]

Shunts are used selectively on the basis of the back-pressure measured in the internal carotid artery (ICA; see the image below). Intraoperative arteriography is an important adjunct if any technical concerns arise with regard to the reconstruction.

ICA is shunted during CCA-to-ICA bypass. CCA = com ICA is shunted during CCA-to-ICA bypass. CCA = common carotid artery; ICA = internal carotid artery.

Bypass and Reconstruction of Carotid

Exposure of cervical carotid artery

For exposure of the cervical carotid artery, a longitudinal incision along the anterior border of the sternocleidomastoid (SCM) is standard. The incision may be extended proximally toward the sternal notch or distally towards the mastoid process as needed. Soft tissue and platysma are divided, and the dissection is carried through the anterior border of the SCM until the carotid sheath is encountered.

If only the lower half of the ICA and the bifurcation require exposure, the internal jugular (IJ) vein is mobilized anteriorly; higher-level dissections are better visualized via a retrojugular approach. The facial vein branch of the IJ vein usually identifies the bifurcation. It is important to identify the hypoglossal nerve (cranial nerve [CN] XII) before dividing this vein because it can run behind and in proximity, particularly in high bifurcations. The vagus nerve (CN X) usually runs in the posterior carotid sheath but can spiral anteriorly and must be identified.

For high exposures of the ICA, the dissection is carried upward toward the mastoid process. Care must be taken to avoid injury to the spinal accessory nerve (CN XI), which enters the SCM at that level. Care must also be taken to identify the superior laryngeal nerve, which hugs the ICA. The posterior belly of the digastric muscle can be divided with impunity.

Further exposure is limited by the styloid process and the mandibular ramus, but these structures can be resected or removed to facilitate more distal access. Anterior subluxation of the mandible allows greater visualization of the distal ICA, which is accomplished by dividing the styloid process.

A common carotid artery (CCA)-to-ICA bypass with a polytetrafluoroethylene (PTFE) graft, performed for aneurysmal disease of the ICA, is shown in the image below.

CCA-to-ICA reconstruction with 6-mm PTFE graft, pe CCA-to-ICA reconstruction with 6-mm PTFE graft, performed for aneurysmal disease of carotid bifurcation. CCA = common carotid artery; ECA = external carotid artery; ICA = internal carotid artery; IJ = internal jugular vein; PTFE = polytetrafluoroethylene.

Exposure of subclavian artery

If arterial inflow is needed from the subclavian artery, supraclavicular exposure of the vessel is most often performed. The skin is incised transversely above the clavicle. Subcutaneous tissue and platysma are divided, and the dissection begins lateral to the jugular vein. The scalene fat pad can be either reflected or excised.

Meticulous ligation of all blood and lymphatic vessels is performed. The phrenic nerve is dissected off the anterior scalene muscle and preserved; the muscle can then be resected. Resection of a portion of the muscle is recommended to prevent reattachment and subsequent compression.

The arteriotomy is made in the superior wall of the subclavian artery. Any plaque at this level is left undisturbed, and any separation of the intima-media layer from the elastic lamina is affixed to the wall and incorporated in the suture line.

The proximal anastomosis is created by using a parachute suturing technique, which allows precise placement of the sutures without any slack in the subclavian artery. The graft is then tunneled to the carotid bifurcation behind the jugular vein ascending parallel to the native CCA.

Exposure of aortic arch

Traditionally, the ascending aortic arch and supra-aortic trunk vessels are approached via a median sternotomy. After the sternum is divided with an oscillating saw, the innominate vein is mobilized and the thymic vessels ligated. The ascending aorta is approached below the innominate vein after the pericardial sac is opened. A partially occlusive side-biting aortic exclusion clamp can be placed without the need for heparinization.

With the clamp secured, the aorta is opened, and the beveled end of the graft is anastomosed to the vessel with a continuous 4-0 or 3-0 polypropylene suture. To prevent air embolization, the patient is placed in the Trendelenburg position, and the anatomosis is tested and vented. If the anastomosis is found to be satisfactory, an occlusive clamp is placed immediately above it, and the table is returned to the original position. The patient is heparinized before the distal anastomosis is begun and after the graft has been tunneled.

An aorta-to-CCA reconstruction for a patient with extensive radiation arteritis of the left CCA is shown in the image below.

Aorta-to-CCA bypass using 8-mm Dacron graft. AA = Aorta-to-CCA bypass using 8-mm Dacron graft. AA = ascending aortic arch; CCA = common carotid artery.

Carotid-to-carotid bypass

If inflow to the CCA is compromised in the mediastinum, donor inflow can be obtained from a healthy contralateral CCA.[15] The bypass between the two CCAs lies low in the midline, extending across the neck through the retropharyngeal space. The tunnel for the bypass is behind the pharynx and in front of the prevertebral fascia. A nonringed prosthesis up to 8 mm in diameter can be tunneled without pharyngeal compression (see the image below).

CT scan demonstrating CCA-to-CCA bypass using retr CT scan demonstrating CCA-to-CCA bypass using retropharyngeal route. CCA = common carotid artery; PTFE = polytetrafluoroethylene (bypass graft).

Complications

Complications of carotid artery bypass and reconstruction include the following:

  • Cranial nerve injury
  • Stroke
  • Thoracic duct leak
  • Bleeding or hematoma
  • Graft thrombosis
  • Graft infection
 

Medication

Medication Summary

Carotid bypass and reconstruction are usually performed with general anesthesia because extensive exposure of the neck and sternotomy may be necessary. If mandibular subluxation is required for high distal targets (C1 and above), nasotracheal intubation is used.

Anesthetic Agents

Class Summary

After standard monitoring equipment is attached and peripheral venous access achieved but before the arterial line is inserted, the midazolam dose is administered. Before placement of the arterial line, it should be ensured that a radial artery graft will not be used for CABG.

Propofol (Diprivan)

Propofol is a phenolic compound unrelated to other types of anticonvulsants. It has general anesthetic properties when administered intravenously. Propofol IV produces rapid hypnosis, usually within 40 seconds. The effects are reversed within 30 minutes following the discontinuation of infusion. Propofol has also been shown to have anticonvulsant properties.

Etomidate (Amidate)

Amidate is a nonbarbiturate imidazole compound with sedative properties. It is short-acting and has a rapid onset of action; the duration of action is dose dependent (15-30 minutes). Its most useful feature as an induction agent is that it produces deep sedation while causing minimal cardiovascular effects.

The major application of etomidate is induction for endotracheal intubation, particularly in patients with, or at risk for, hemodynamic compromise. Amidate has been shown to depress adrenal cortical function; however, this effect is not significant clinically during short-term administration. Since the drug is mixed in propylene glycol, continuous infusion not recommended.

Thiopental

Thiopental is a short-acting barbiturate sedative-hypnotic with rapid onset and a duration of action of 5-20 minutes. Like methohexital, it is most commonly used as an induction agent for intubation. To use thiopental as a sedative, titrate in dosage increments of 25 mg (adjust to lower dose in children).

Isoflurane (Forane, Terrell)

Isoflurane is an inhalation anesthetic. It may have a myocardial protective effect and therefore is especially useful in off-pump surgery. Isoflurane potentiates the effects of muscle relaxants. Small doses of muscle relaxants can achieve complete paralysis when administered concomitantly with isoflurane.

Neuromuscular Blockers, Nondepolarizing

Class Summary

Nondepolarizing neuromuscular blockers are used in combination with a sedative as part of the rapid-sequence intubation process.

Pancuronium

Vecuronium may increase myocardial oxygen demand. It is used to facilitate endotracheal intubation and provide neuromuscular relaxation during intubation and mechanical ventilation. It is given as an adjunct to a sedative or hypnotic agent.

Vecuronium

Vecuronium may cause bradycardia in association with opioids. It is used to facilitate endotracheal intubation and provide neuromuscular relaxation during intubation and mechanical ventilation. It is given as an adjunct to a sedative or hypnotic agent.

Rocuronium (Zemuron)

Rocuronium may cause tachycardia. It is used to facilitate endotracheal intubation and provide neuromuscular relaxation during intubation and mechanical ventilation. It is given as an adjunct to a sedative or hypnotic agent.

Atracurium

Atracurium is not considered suitable for operations of long duration. It can cause hypotension secondary to histamine release. It is used to facilitate endotracheal intubation and provide neuromuscular relaxation during intubation and mechanical ventilation. It is given as an adjunct to a sedative or hypnotic agent.