Carotid Endarterectomy

Patient Selection

35.1.1 Carotid Stenosis

The North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial found that carotid endarterectomy (CEA) significantly decreased the incidence of ipsilateral stroke among patients with symptomatic carotid stenosis with greater than 70% carotid stenosis compared to medical management. ¹^, ² In addition, the latter study found that for a subset of high-risk patients, there was benefit of CEA for patients with high–moderate (50–69%) carotid stenosis. Several randomized clinical trials have also found that CEA reduces the risk of ipsilateral stroke in asymptomatic patients with greater than 60% stenosis. ³^, ⁴ For symptomatic patients, the benefit from CEA is greatest when it is performed within 2 weeks of the transient ischemic attack (TIA) or minor stroke. ⁵

35.1.2 Carotid Occlusion

The efficacy of CEA in patients with carotid occlusion or near-occlusion is controversial and metaanalysis of data from randomized clinical trials concluded that evidence to support CEA in this setting was lacking but the number of patients studied was very limited. ⁶ Nevertheless, it is our practice to operate in the setting of subacute and chronic carotid occlusion, particularly if there is any suggestion of a “string sign” on carotid angiography that may be consistent with carotid patency and the patient is symptomatic and not disabled ( ▶ Fig. 35.1).

Fig. 35.1 Anterior–posterior projection of a common carotid injection demonstrating near-complete vessel occlusion and angiographic “string sign” along the proximal internal carotid artery just distal to the carotid bifurcation.

35.1.3 Carotid Stenting

Carotid angioplasty and stenting (CAS) with or without distal protection devices has been suggested as an alternative to CEA. ⁷^, ⁸^, ⁹ The decision to treat carotid stenosis by CEA or CAS is controversial. In general, randomized clinical trials comparing these procedures have shown that both reduce the risk of stroke, although it is not clear if non-inferiority of CAS compared to CEA has been demonstrated. ⁹ CAS is associated with a higher risk of periprocedural stroke whereas CEA is associated with a higher risk of periprocedural myocardial infarction. Restenosis may be more common after CAS.

In general, the most widely accepted indications for CAS are patients with multiple medical illnesses, high anesthetic risk, restenosis after prior CEA, radiation-induced stenosis, and anatomical variations principally a very high carotid bifurcation. We remain unconvinced, particularly in regards to the elderly patient population, that CAS provides any tangible benefit to patients with carotid stenosis. In our series of patients older than 70 years, we found no difference in surgical outcome and further posit that the more friable and tortuous vessels commonly encountered in older patients only serve to complicate endovascular navigation. ¹⁰

35.2 Preoperative Evaluation

35.2.1 Imaging Studies

There is no consensus regarding the appropriate preoperative vascular imaging required prior to CEA. At our institution, the diagnosis of carotid stenosis must be confirmed either by carotid duplex ultrasound or computed tomography arteriogram (CTA). CT or catheter angiography are required before surgery. CTA is usually sufficient for surgical planning. If there is any ambiguity about the vascular anatomy, or if carotid bulb calcification renders the CTA insensitive, then we obtain a catheter angiogram—which remains the gold standard for preoperative evaluation of carotid stenosis.

35.2.2 Medical Management

Anticoagulation and Antiplatelet Therapy

Meta-analyses of several randomized controlled trials have demonstrated that antiplatelet therapy with aspirin reduces the risk of stroke of any cause in patients undergoing CEA. ¹¹ Patients with carotid stenosis may also be prescribed clopidogrel or warfarin for various indications; however, there is no direct evidence that either of those medications reduces the incidence of thromboembolic stroke related to carotid stenosis. Statins (HMG-CoA reductase inhibitors) may reduce carotid plaque progression and the incidence of transition from asymptomatic to symptomatic carotid stenosis. Other studies have also reported a clinically significant decrease in perioperative morbidity and mortality when patients are treated with a statin prior to CEA. ¹² Therefore, it is our practice to recommend that all patients with carotid stenosis take daily aspirin, a recommendation based on robust high-quality data, and a statin, based on more limited lower quality evidence, unless there are pharmacologic contraindications. ¹³

35.3 Operative Procedure

35.3.1 Positioning

The patient is positioned supine; the head cradled in a foam donut cushion and five to six towels are placed between the patient’s shoulder blades to induce gentle cervical extension. The head is then turned approximately 15 to 30 degrees—depending on the relationship between the external carotid artery (ECA) and the internal carotid artery (ICA)—contralateral to the surgical side in order to maximize the distance between the jaw and the clavicle. Greater head rotation is required when the ICA is medially rotated (i.e., “hidden,” or tucked underneath the ECA).

Two anatomical landmarks are identified on the preoperative radiographic studies to estimate the rostral extent of the required exposure. The first is the angle of the mandible, which is palpated and marked before skin incision. The second is the position of the carotid bifurcation, particularly its relationship with the distal extent of the cervical plaque.

35.3.2 Anterior Cervical Dissection

A longitudinal incision is marked parallel to the anterior margin of the sternocleidomastoid muscle and is extended according to anatomic landmarks discussed previously—sometimes as low as the sternal notch and other times as high as the posterior auricular area ( ▶ Fig. 35.2). The skin is infiltrated with local anesthetic prior to incision with a number 15-blade scalpel. The platysma is opened sharply, also in the rostral-caudal plane. The edge of the sternocleidomastoid is identified and retracted laterally. A blunt Wietlaner, self-retaining retractor is used to maintain the exposure. The retractor is placed superficially on the medial aspect of the incision to prevent injury to the laryngeal nerves, but more deeply on the lateral aspect of the incision.

Fig. 35.2 A vertically oriented incision parallels the medial aspect of the sternocleidomastoid muscle. The L-shaped mark denotes the angle of the mandible.

Once deep to the investing fascia, the common facial vein is commonly encountered. This vessel is ligated with two 2–0 silk ties and sharply divided. Dissection continues along the anterior border of the internal jugular vein until the common carotid artery (CCA) is identified proximal to its bifurcation. The carotid sheath is typically opened just above the superior belly of the omohyoid muscle, but in the rare case of a low-lying carotid bifurcation, the omohyoid muscle may be divided with bipolar electrocautery and Metzenbaum scissors. When dividing the omohyoid, a stitch may be placed at the muscle edges to aid in reapproximation at the end of the procedure.

A blunt-toothed, self-retaining retractor can be used to retract the internal jugular vein away from the CCA, although one must be careful to avoid the vagus nerve. As seen in ▶ Fig. 35.3, we now prefer blunt fish-hooks attached to a retaing ring to secure the exposure and prevent nerve damage from retractor use. Once the carotid sheath is opened, a 0 silk tie is placed around the proximal CCA, secured with a Rummel tourniquet, to achieve proximal vascular control.

Carotid Exposure

A strict, “minimum-touch” technique is applied with respect to the CCA to prevent dislodgement of an atheromatous plaque. When the CCA is first identified, 5,000 units of intravenous heparin are administered by anesthesia. Infrequently, dissection along the carotid bifurcation elicits hemodynamic instability. If there is blood pressure lability, then the carotid sinus may be injected with 2 mL 1% Xylocaine (AstraZeneca, Wilmington, DE) via a 25-gauge needle.

The dissection of the carotid complex is completed when the surgeon has isolated the CCA, ECA, and ICA, each of which is then encircled with 0-silk ties or vessel loops. It is critically important to expose the ICA beyond the end of the plaque. The superior thyroid artery is also routinely identified during the anterior cervical dissection and may be controlled with an encircling 2–0 silk tie. The CCA is prepared for proximal control by placement of a Rummel tourniquet that facilitates constriction of the vessel around an intraluminal shunt, if necessary.

The carotid plaque is identified by correlating intraoperative visual cues to landmarks noted on and measurements derived from the preoperative angiogram. The yellowish wall of the atherosclerotic carotid artery turns a pinkish-blue distal to the atheroma and it is critical to obtain distal control well beyond the plaque so as not to precipitate arterial thrombi. During exposure of the ICA, a 0-silk suture is passed around it and a Loftus encircling shunt clamp (Scanlan International, St. Paul, MN) is tested around the ICA in case shunting is required. Adequate proximal exposure of the CCA is necessary because the vessel loops are placed 1 cm distal to the area of the DeBakey cross-clamp and the clamp must be placed far enough inferiorly on the CCA so as to facilitate bloodless shunt placement.

35.3.3 Endarterectomy

After adequate proximal and distal vascular control is obtained, a sterile marking pen defines the intended arteriotomy ( ▶ Fig. 35.3). A bulldog clamp is then used to occlude first the ICA. Next, the DeBakey cross-clamp is used to occlude the CCA. Finally, a second bulldog clamp is applied across the lumen of the ECA. Next, a number 15-blade knife is used to make a stab incision in the proximal CCA. Potts scissors are then used to extend the incision rostrally—taking care to stay in the middle of the lateral exposure of the carotid artery, away from the apex of the bifurcation—until normal vessel lumen is identified.

The arteriotomy and endarterectomy are performed under 3.5x loupe-magnification. Some surgeons use the operating microscope. We use both EEG and SSEP monitoring on these cases. We do not use a shunt in every case, but rather determine whether a shunt is indicated based predominantly on whether there is adequate collateral perfusion of the ipsilateral cerebral hemisphere based on preoperative vascular imaging and whether carotid cross-clamping has any affect on the EEG or SSEP monitoring. Changes in the EEG or SSEP mandate a trial of induced hypertension facilitated by anesthesia; however, if there is no immediate improvement in the EEG or SSEP recording, then an intraluminal shunt is placed.

We use the custom, #10F Loftus CEA shunt of our own design (Integra NeuroCare, Plainfield, NJ). The shunt is first inserted into the CCA and the Rummel tourniquet is tightened around it, then the remaing shunt is passed more proximally into the CCA after the DeBakey clamp has been opened. This method eliminates bleeding from opening the clamp because the tourniquet has already been secured. The distal end is opened to confirm blood flow and to clear any debris from the tubing. The shunt is then inserted in the ICA and secured with the Loftus shunt clamp ( ▶ Fig. 35.4). ¹⁴ A handheld Doppler is applied to the tubing to auscultate flow.

Plaque removal begins with a Freer elevator (Sklar Instruments, West Chester, PA) or Scanlan plaque dissector (Scanlan Instruments, St. Paul, MN), either of which may be used gently to develop a cleavage plane between the atheromatous plaque and intimal layer of the vessel wall ( ▶ Fig. 35.5). Dissection begins at the rostral aspect of the plaque and continues caudally in a circumferential manner. Meticulous dissection prevents breaching through the lateral aspect of the vessel wall. If the plaque extends proximally into the CCA and no feathered edges are readily identified, then the plaque is transected sharply with either a number 15-blade knife or tenotomy scissors. If the dissection is taken superiorly enough, then the atheromatous plaque usually feathers distally into the ICA and can be easily removed. In some cases, however, at the distal endpoint the plaque may leave a “shelf” with tattered edges that must be cleaned, the edges of which must be tacked down with 6–0 Prolene (Ethicon Inc., New Brunswick, NJ) sutures to prevent arterial dissection. After separation of the plaque from the ICA and the CCA, the remaining plaque is secured with vascular forceps and removed from the ECA. If there is any question of residual plaque, then a separate arteriotomy and primary repair of the ECA should be undertaken.

Fig. 35.3 The carotid vessels are isolated and prepared for arteriotomy. Exposure of the internal carotid artery is continued cranially until the surgeon ensures that the intended arteriotomy will extend well above the rostral extent of the plaque. A blue line, demarcating the intended arteriotomy, is useful in preventing a jagged carotid opening, which is difficult to close. Note the presence of a Rummel tourniquet already in its appropriate position, proximally on the common carotid artery.

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