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Acs0609 Surgical Treatment Of Carotid Artery Disease
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Acs0609 Surgical Treatment Of Carotid Artery Disease Document Transcript

  • 1. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 1 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE Wesley S. Moore, M.D., F.A.C.S. The rationale for operating on patients with carotid artery disease method rather than the European method. Moreover, it was deter- is to prevent stroke. It has been estimated that in 50% to 80% of mined by means of contrast angiography rather than duplex ultra- patients who experience an ischemic stroke, the underlying cause sonography (DUS) or magnetic resonance imaging. If the decision is a lesion in the distribution of the carotid artery, usually in the for CEA is to be based on DUS, some conversion of values is vicinity of the carotid bifurcation. It would follow, then, that required. A patient who has an 80% to 99% stenosis on DUS can appropriate identification and intervention could significantly generally be assumed to have a diameter-reducing stenosis of at reduce the incidence of ischemic stroke. least 60% on angiography; a stenosis that is less than 80% on DUS Carotid endarterectomy (CEA) for both symptomatic and may fall short of a 60% diameter-reducing stenosis on angiography. asymptomatic carotid artery stenosis has been extensively evaluat- ed in prospective, randomized trials. Symptomatic patients have Symptomatic Hemodynamically Significant Carotid Stenosis been studied in the North American Symptomatic Carotid Both NASCET and ECST found that symptomatic patients Endarterectomy Trial (NASCET),1 the European Carotid Stenosis with hemodynamically significant stenoses experienced fewer fatal Trial (ECST),2 and the symptomatic carotid stenosis trial from the and nonfatal strokes after CEA combined with best medical man- Veterans Affairs (VA) Cooperative Studies Program.3 The results of agement than after best medical management alone, provided that all three trials conclusively demonstrate that symptomatic patients the perioperative morbidity and mortality from stroke was 6.0% with greater than 50% stenosis on arteriography are at substantial- or less. Thus, patients with monocular or hemispheric TIAs are ly lower risk for stroke after CEA than control subjects receiving good candidates for CEA. Global ischemic attacks have also been medical management alone. Asymptomatic patients with hemody- used as an indication for CEA. This practice has not been evalu- namically significant stenosis also benefit from surgical treatment: tated in clinical trials; it is usually justified on the basis of the the Asymptomatic Carotid Atherosclerosis Study (ACAS)4 and the ACAS data alone. asymptomatic carotid stenosis trial from the VA Cooperative Patients who have previously experienced a hemispheric stroke Studies Program5 show that the risk of both transient ischemic but who are not disabled and have made a reasonable recovery are attacks (TIAs) and stroke is markedly lower in patients treated with also good candidates for CEA if they have a hemodynamically sig- CEA and best medical management than in control subjects treat- nificant stenosis. ed with best medical management alone. The Medical Research IMAGING Council study of the Asymptomatic Carotid Stenosis Trial (ACST) confirmed the findings of these two studies, citing results virtually Identification of a carotid lesion that can be treated with endar- identical to those originally reported by ACAS.6 terectomy usually begins with a carotid duplex scan. Indications Surgical reconstruction of the carotid artery yields the greatest for carotid duplex scanning fall into three main categories: symp- benefits when done by surgeons who can keep complication rates toms, signs, and risk factors. Symptoms include classic TIAs and to an absolute minimum. The majority of complications associat- strokes that give rise to clinical suspicion of carotid bifurcation dis- ed with carotid arterial procedures are either technical or judg- ease.The primary sign is the presence of a carotid bruit on auscul- mental; accordingly, in what follows, I emphasize the procedural tation. Risk factors include cigarette smoking, hypertension, dia- details that I consider particularly important for deriving the best betes mellitus, hypercholesterolemia, peripheral vascular disease, short- and long-term results from surgical intervention. and coronary artery disease. As the number of risk factors present increases, the likelihood of associated carotid bifurcation disease increases exponentially. Preoperative Evaluation Patients who present with focal ischemic symptoms are likely to have associated carotid bifurcation disease; however, other patho- PATIENT SELECTION logic conditions (e.g., emboli of cardiac origin, aortic arch disease, Indications for carotid artery surgery can be divided into two intracranial vascular disease, coagulopathy, and brain tumors) can major categories: (1) asymptomatic critical stenosis and (2) symp- also be responsible for focal symptoms. Accordingly, a complete tomatic hemodynamically significant stenosis.7 workup of a symptomatic patient should include cardiac evalua- tion as well as intracranial imaging. Asymptomatic Critical Stenosis The accuracy of carotid duplex scanning is highly dependent on The VA asymptomatic carotid stenosis study, ACAS, and ACST the technician performing it and on the laboratory where it is all found that in patients with diameter-reducing stenosis of 60% done. A carefully performed carotid duplex scan is often the most or greater on angiography, CEA resulted in fewer fatal and nonfa- accurate indicator of carotid bifurcation disease; however, a hasti- tal strokes over a 5-year period than nonoperative treatment with ly or carelessly performed scan can result in overestimation of the best medical management alone. It is important to keep in mind extent of the carotid bifurcation disease. For this reason, addition- that there are several different ways of measuring stenosis [see 6:2 al imaging studies (e.g., magnetic resonance angiography, com- Asymptomatic Carotid Bruit]. The 60% figure cited by ACAS and puted tomographic angiography, and, when there is serious doubt, the VA study was determined according to the North American contrast angiography) may be indicated.
  • 2. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 2 surgeon may well work better and achieve better results with one technique or the other. Whichever anesthetic approach is used, all patients should have a radial arterial line in place to allow continuous blood pressure monitoring and to provide access for determining blood gas levels. As a rule, there is no need to place a central venous line or a right heart catheter, except in patients with marginal cardiac function. PATIENT POSITIONING Proper positioning of the patient is necessary to provide opti- mal exposure of the neck from the clavicle up to the mastoid process on the side of the proposed operation [see Figure 1]. The patient is placed in the supine position with a folded sheet under the shoulders to induce a mild degree of neck extension. Excessive neck extension should be avoided, however, because it places ten- sion on the artery and actually hinders rather than facilitates exposure.This potential problem can be addressed by placing one Figure 1 Carotid arterial procedures. Shown is the recommend- or more towels under the head to adjust the neck to the optimal ed patient positioning. degree of extension. The patient’s head is then turned away from the side of the operation to improve cervical exposure further. Finally, the table top may be rotated slightly away from the side of Operative Planning the operation so as to provide a flat surgical field.The head of the table may be elevated slightly if the patient’s blood pressure is ade- Before operation is scheduled, the general health of the patient quate; this step helps lower venous pressure and reduce venous must be assessed, with particular attention paid to cardiac and pul- bleeding during the operation [see Figure 1]. monary status. Given that many patients with carotid artery disease are hypertensive or diabetic, good preoperative control of diabetes mellitus and blood pressure is mandatory. In addition, to reduce Operative Technique the risk of thromboembolic complications, patients should receive antiplatelet drugs (e.g., aspirin) up to and on the day of operation. STEP 1: INITIAL INCISION Finally, it is well documented that the risk of perioperative cardiac Either of two incisions may be used for exposure of the cervi- complications can be materially reduced by placing patients on a cal carotid artery. The more common choice is a vertical incision combination regimen that includes a statin and a beta blocker. placed along an imaginary line that extends from the sternoclav- ANESTHESIA icular junction to the mastoid process, paralleling the anterior margin of the sternocleidomastoid muscle as well as the course of Surgery on the cervical portion of the carotid artery may be the carotid artery and the contents of the carotid sheath [see Figure performed with the patient under either general or cervical block 2]. The incision is centered over the presumed location of the anesthesia. Both techniques have their advocates, their advan- carotid bifurcation. The advantage of this incision is that it pro- tages, and their disadvantages. The advantages of general anesthesia include a quiet operative field, maximal patient comfort, and good airway control. In addi- tion, general anesthesia may lead to improved cerebral blood flow and give better protection against reduced blood flow during carotid clamping.The disadvantages of general anesthesia include blood pressure swings during induction and the inability to moni- tor the patient’s conscious response to carotid clamping. Some reports also suggest that the incidence of cardiac complications is higher during general anesthesia than during cervical block anesthesia. The main advantage of cervical block anesthesia is the ability to monitor cerebral function during carotid clamping: an awake patient can be engaged in conversation and can be asked to carry out motor activities of the extremities.The disadvantages of cervi- cal block anesthesia include possible patient discomfort, restless- ness, and intolerance of the longer operations that are sometimes necessary for technical reasons. Another disadvantage is that on occasion, a patient cannot tolerate carotid clamping and demon- strates an immediate neurologic deficit with clamp application. Such an occurrence heightens the anxiety level of the surgical team, thereby increasing the risk that they will commit technical Figure 2 Carotid arterial procedures. The incision most com- errors in the rush to place an internal shunt. monly used to expose the cervical carotid artery is a vertical one Besides considering the inherent advantages and disadvan- placed along the anterior margin of the sternocleidomastoid mus- tages of these two anesthetic techniques with respect to the cle and centered over the presumed location of the carotid bifur- patient, it is important to consider their advantages and disad- cation. It may be extended proximally or distally, depending on vantages with re- spect to individual surgical practice. A given where the carotid bifurcation turns out to be.
  • 3. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 3 Skin flaps are raised in a subplatysmal layer, and the incision is deepened along the anterior border of the sternocleidomastoid muscle. The advantage of this alternative incision is that it may be more cosmetically acceptable; however, its inferior portion fre- quently crosses the neck anteriorly, which may make it more visible than an incision confined to the line of the sternocleidomastoid muscle would be.The disadvantage of this incision is that it requires the raising of skin flaps, which takes additional time and may limit the extent of any proximal exposure that may be required. STEP 2: EXPOSURE OF CAROTID ARTERY Once the incision through the platysmal layer has been com- pleted, an avascular areolar plane is developed along the anterior border of the sternocleidomastoid muscle for the full length of the incision so as to expose the carotid sheath. The internal jugular vein is usually the most visible vessel, and the carotid sheath is opened along this vessel’s anterior border. The common facial Figure 3 Carotid arterial procedures. An alternative incision to vein, which drains into the internal jugular vein, is a relatively con- the vertical incision is a transverse incision along a skin crease in stant landmark. Because the common facial vein is the venous the vicinity of the carotid bifurcation. analogue of the external carotid artery, it can generally be used as a guide to the position of the carotid bifurcation [see Figure 4]. On vides optimal exposure of the cervical carotid artery and can read- occasion, a patient has several accessory facial veins instead of a ily be extended either proximally or distally along the aforemen- single common facial vein. The common facial vein or the acces- tioned imaginary line to give additional exposure when needed sory facial veins are then divided between ligatures so that the (e.g., when the carotid bifurcation is unusually high). The disad- jugular vein can be retracted laterally.The common carotid artery vantage of this incision is that it runs against Langer’s lines; thus, and the carotid bifurcation lie immediately beneath the divided if a keloid occurs, it is likely to be in an unsightly position. In most facial veins. patients, the incision heals to a fine line, and it usually is not At this point, care must be taken to look for the vagus nerve. noticeable once healing is complete. This nerve is usually located posterior to the common carotid The alternative to the vertical incision is a transverse incision that artery, but it is sometimes rotated into a more superficial posi- is placed in a skin crease on the anterior portion of the neck and tion. Another important neurologic structure in this area is the then curved toward the mastoid process posteriorly [see Figure 3]. ansa cervicalis, which is formed by the junction of fibers from the hypoglossal (12th cranial) nerve and fibers from the first cer- vical nerve and which continues inferiorly as a single trunk, pro- viding innervation to the strap muscles. This nerve should be Common spared if possible, but it can be divided without significant Facial Vein sequelae if it interferes with optimal exposure of the carotid bifurcation. One convenient method of separating the nerve from the artery is to divide the fibers running from the first cervical nerve to the ansa cervicalis; when this is done, the nerve is readily mobilized and retracted anteriorly away from the carotid artery. The perivascular plane of the common carotid artery is then entered, and the common carotid artery is circumferentially mobi- Internal lized.The common carotid artery is palpated against a right-angle Jugular Vein clamp to determine the proximal extent of the atherosclerotic plaque. If possible, the common carotid artery should be mobi- lized proximal to the plaque until a circumferentially soft portion Common of that vessel is reached. During mobilization, the vagus nerve Carotid Artery should be identified in its usual location posterior to the vessel and carefully protected; this nerve sometimes spirals anterior to the carotid artery as the vessel is dissected distally. Dissection is then extended distally toward the carotid bifurca- tion and continued along both the internal and external carotid arteries. Excessive manipulation of the area around the carotid bifurcation must be avoided. In particular, it is important to be careful around the bulb of the internal carotid artery: this is where the majority of the plaque will be located, and manipulation can easily dislodge plaque or thromboembolic material.With exposure Figure 4 Carotid arterial procedures. After the sternocleidomas- of the carotid bifurcation, the hypoglossal nerve may come into toid muscle is mobilized off the carotid sheath, the jugular vein is view. Care should be taken not to injure this nerve, though it may identified. The perivascular plane along the jugular vein is opened have to be mobilized to permit sufficient distal exposure of the until the common facial vein is exposed. internal carotid artery.
  • 4. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 4 a The jugular vein is mobilized up toward the base of the skull, with care taken to look for additional accessory facial branches, which must be divided between ligatures so that the jugular vein can be fully mobilized and moved posteriorly. The perivascular plane of the internal carotid artery is carefully defined, and the artery is gently mobilized; the more distal portion of the internal carotid artery can then be mobilized downward. If the vessel is still insufficiently mobile, then the nerve to the carotid body and the ascending pharyngeal artery within the crotch between the inter- nal and external carotid arteries are mobilized and divided b between ligatures. These two structures often serve as a de facto suspensory ligament for the carotid bulb; dividing them allows the carotid bifurcation to drop down and permits further downward traction of the internal carotid artery as the vessel is gently mobi- lized distally [see Figure 6]. Once the internal carotid artery is further exposed distally and the hypoglossal nerve is mobilized along its vertical portion and moved anteriorly, the posterior belly of the digastric muscle is encountered. An areolar plane is developed posteriorly and supe- riorly along the inferior margin of the posterior belly of the digas- tric muscle, allowing the muscle to be mobilized anteriorly to yield additional exposure of the internal carotid artery. If the Ascending Pharyngeal Artery Autonomic Nerve to Carotid Body a Bulb of Internal Carotid Artery Figure 5 Carotid arterial procedures. After the common carotid artery and the internal and external carotid arteries have been mobilized, the internal carotid artery is palpated against a right- angle clamp in at least two planes (a, b) to confirm that the artery has been freed beyond the end point of the plaque. Next, dissection is continued distally beyond the bulb of the internal carotid artery to a point where the internal carotid artery is normal. At this point, the relevant portion of the vessel b is circumferentially mobilized and palpated against a right-angle clamp in at least two planes to confirm that the atheromatous plaque does not reach up to the level of the proposed clamping [see Figure 5]. Once this is accomplished, the external carotid artery is mobilized beyond the end point of plaque extension in a similar manner. If the patient has a high carotid bifurcation or if the plaque in the internal carotid artery extends further distally than usual, a more extensive exposure of the carotid bifurcation, the internal carotid artery, or both is required. To provide such Figure 6 Carotid arterial proce- exposure, the skin incision is extended all the way to the mas- dures. Once the common, internal, toid process.The sternocleidomastoid muscle is fully mobilized and external carotid arteries are up to the mastoid process, with care taken to look for the spinal fully mobilized, the structures portion of the accessory (11th cranial) nerve as it enters the between the internal and external sternocleidomastoid muscle on the medial surface. With the carotid arteries (a) are divided (b) sternocleidomastoid muscle fully mobilized and retractors in to allow the carotid bifurcation to place, the internal carotid artery can then be further exposed. drop down.
  • 5. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 5 Middle Meningeal Artery Point of Division of Styloid Process Sternocleidomastoid Muscle Point of Division of Posterior Belly of Digastric Muscle Above Digastric 1. Superficial Temporal Artery 2. Internal Maxillary Interior Carotid Artery Artery 3. Posterior Auricular Artery Digastric Muscle Below Digastric Exterior Carotid Artery 1. Occipital Artery 2. Ascending Pharyngeal Artery 3. Facial Artery 4. Lingual Artery 5. Superior Thyroid Artery Inferior Alveolar Artery Submental Artery Vertebral Artery Omohyoid Muscle Common Carotid Artery Sternocleidomastoid First Rib Muscle Figure 7 Carotid arterial procedures. Division of the posterior belly of the digastric muscle yields addi- tional exposure of the internal carotid artery. If the internal carotid artery must be mobilized all the way to the base of the skull, further distal exposure is obtained by separating the attachments of the ligaments to the styloid process and dividing the styloid process. resulting exposure is not sufficient, the muscle may be carefully Additional adjunctive measures for more extensive exposure of encircled with a right-angle clamp and divided [see Figure 7]. In the internal carotid artery have been described.These include sub- those relatively uncommon cases in which even further distal luxation or dislocation of the mandible,8 wiring of the mandible exposure is required, the styloid process is palpated and the into a subluxed position, and division of the ramus of the mandible muscular and ligamentous attachments to the styloid process with rotation of the mandible away from the base of the skull. In divided, so that the styloid process can be exposed with a my view, these measures are unnecessary, provided that the stern- periosteal elevator. Once the styloid process has been complete- ocleidomastoid muscle and the jugular vein have been adequately ly freed of its muscular and ligamentous attachments and the mobilized, the plane around the internal carotid artery has been cranial nerves in the vicinity have been identified and carefully developed, and the carotid bifurcation has been released. protected, the styloid process is cut close to the base of the skull A significant risk associated with extended exposure of the [see Figure 7]. This step yields optimal exposure of the internal internal carotid artery is possible injury to the vagus nerve, the carotid artery all the way to the base of the skull. accessory nerve, or the hypoglossal nerve. Retraction of the vagus
  • 6. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 6 nerve may produce either temporary or permanent vocal cord a palsy, and extensive retraction of or injury to the hypoglossal nerve Anterior Communicating Artery causes denervation of the ipsilateral side of the tongue, manifest- Middle Cerebral Artery ed by tongue deviation to the ipsilateral side on protrusion or dif- ficulty with mastication or swallowing. In addition, posterior expo- P1 sure of a high carotid bifurcation may result in injury to branches of the glossopharyngeal (ninth cranial) nerve. Posterior Cerebral Artery A common error in carotid artery mobilization is failure to rec- ognize that the plaque in the internal carotid artery extends beyond the upper limit of the arterial exposure. It is far better to anticipate this problem before clamping and opening the artery Basilar Artery than to discover it afterward and be forced to mobilize the vessel after it has been clamped. Once the common carotid and internal carotid arteries have been mobilized sufficiently, they are encircled with umbilical tapes; Rumel tourniquets are used if an internal b shunt is required or desired. STEP 3: CEREBRAL CIRCULATORY SUPPORT Clamping of the carotid artery necessarily results in interruption of blood flow through the vessel. Patients who have good collateral circulation via the contralateral carotid artery or the vertebral arter- P1 ∝ P2 ies generally (though not always) tolerate the temporary interrup- tion of flow through the clamped artery well.9 Patients who have inadequate collateral blood flow require cerebral circulatory sup- port, usually in the form of placement of an internal shunt. There Internal Carotid are three basic approaches to shunt use: (1) routine use of an inter- Artery nal shunt, (2) selective use of an internal shunt, and (3) routine avoidance of shunting in an attempt to minimize clamp time. Shunting Options Routine shunting In approximately 10% of patients under- going carotid artery surgery, collateral blood flow is inadequate and temporary use of an indwelling shunt is necessary to prevent brain damage. In the remaining 90%, collateral blood flow is ade- quate and clamping generally well tolerated, and shunting is there- fore unnecessary. Clearly, routine use of an internal shunt takes P2 Clamp care of the 10% of patients who require shunts. Its disadvantage is that it is an additional procedure that carries its own complica- tions, to which not only the 10% of patients who require shunting but also the 90% who do not are subjected.The potential compli- cations associated with placement of a shunt include intimal injury (including the raising of an intimal flap), atheroma embolization (if atheromatous material is scooped up during shunt placement), and air embolization (if air bubbles are trapped within the shunt Figure 8 Carotid arterial procedures. (a) Shown is a graphic and not recognized). representation of the measurement of internal carotid artery back-pressure. (b) The needle is bent at a 45º angle before being Selective shunting Selective placement of a shunt has an inserted into the common carotid artery. advantage over routine placement in that the procedure and its potential complications are limited to the 10% of patients who actually require a shunt. Its main disadvantage is that the methods bral blood flow is measurement of back-pressure in the internal used to identify patients who require shunting may not be entire- carotid artery.10 Back-pressure has been shown to be a good index ly reliable. of the adequacy of collateral blood flow, and it correlates well with Selective identification of patients who require shunting can be the safety of temporary clamping and thus with the necessity of accomplished in several ways. The most direct—and perhaps placing an internal shunt. Back-pressure is measured by placing safest—method is to employ local or cervical block anesthesia so into the common carotid artery a needle that is connected to pres- that the effect of temporary carotid clamping can be assessed in a sure tubing and a pressure transducer.The tip of the needle is bent conscious patient; if clamping leads to a neurologic deficit, then the at a 45° angle. Systemic blood pressure is measured, and clamps patient clearly requires an internal shunt. Other methods of identi- are placed on the common carotid artery proximal to the needle fying patients who require a shunt make use of techniques such as and on the external carotid artery. The residual pressure in the continuous electroencephalographic monitoring, measurement of common carotid artery, which is in continuity with the internal somatosensory evoked potential, and monitoring of middle cere- carotid artery, is then allowed to equilibrate; the resulting pressure bral blood flow with transcranial Doppler ultrasonography. reading represents internal carotid artery back-pressure [see Figure A useful method of determining the adequacy of collateral cere- 8]. It has been determined that patients with back-pressures high-
  • 7. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 7 Ischemic Penumbra Anterior Cerebral Arteries Infarct Zone Embolus in Artery Collateral Blood Supply to Ischemic Penumbra Middle Cerebral Arteries Posterior Cerebral Artery Figure 9 Carotid arterial procedures. When a thromboembolic fragment occludes a cortical arterial branch, a central infarct zone develops, surrounded by an ischemic zone that derives some residual blood supply from collateral vessels. In this zone, known as the ischemic penumbra, the residual blood supply is sufficient to maintain viability. er than 25 mm Hg can tolerate temporary clamping without on the shunt and briefly opened to allow back-bleeding; good incurring brain damage. back-bleeding confirms that the shunt is lying free in the lumen of The utility of selective shunting in appropriate settings notwith- the internal carotid artery. The shunt is then secured by tighten- standing, routine shunting is recommended for patients who have ing a Rumel tourniquet, and the bulbous portion of the shunt is previously had a stroke, regardless of the degree of neurologic engaged to prevent dislodgment. recovery. In these patients, a central area of cerebral infarction is Next, the proximal portion of the shunt is placed into the com- surrounded by a zone of relatively ischemic tissue—the so-called mon carotid artery. As this is done, the clamp is removed from the ischemic penumbra. The ischemic penumbra is made up of live shunt so that backflow from the shunt will dislodge any loose and potentially functional brain tissue, but its viability is highly material and air within the common carotid artery. The shunt is dependent on maximization of cerebral perfusion pressure then reclamped, and the clamp is removed from the common through collateral channels. Accordingly, any interruption of carotid artery as the proximal portion of the shunt is passed into carotid circulation, regardless of the degree of collateral circula- that vessel. tion present, may threaten the ischemic penumbra and extend the When the proximal portion of the shunt is in the proper posi- infarct [see Figure 9]. In my opinion, all CEA patients with prior tion in the common carotid artery, it is secured by tightening a strokes should receive shunts on a routine basis. Rumel tourniquet on the vessel. The clamp on the shunt is then slowly opened so that the surgeon can observe flow through the Routine avoidance of shunting The advantage of routine- translucent device and thus verify that no solid particles or air ly avoiding the use of shunts is that the technical issues and poten- bubbles are passing through it. Because the shunt is relatively tial complications associated with the additional procedure are long, the surgeon has a reasonable amount of time in which to avoided entirely.The disadvantage is that unshunted patients with observe flow. If any particles or air bubbles are identified, the poor collateral blood flow may sustain ischemic brain damage, shunt can be quickly clamped, removed from the common particularly if the clamp time turns out to be longer than was carotid artery, and back-bled, and the procedure can then be anticipated. repeated. Once the shunt is secured in place and open, its length and Technique of Shunt Placement redundancy allow it to be easily manipulated medially and lateral- Internal shunts must be placed with great care if shunt-associ- ly; endarterectomy can then be performed without the encum- ated complications are to be avoided. Of the various shunts cur- brance of an inlying shunt. rently available, I prefer the Javid shunt, which is tapered, has STEP 4: RECONSTRUCTION OPTIONS smooth leading edges, and possesses external bulbous circumfer- ential extensions that permit it to be held in place with a circum- There are four principal reconstructions involving the com- ferential Rumel tourniquet, thereby minimizing the chances of mon carotid artery and the carotid bifurcation: (1) convention- inadvertent dislodgment. Optimal placement of an internal shunt al open CEA with either patch angioplasty or primary closure, may be achieved by means of the following steps [see Figure 10]. (2) eversion endarterectomy, (3) reconstruction for proximal After the patient has been adequately heparinized and the lesions of the common carotid artery, and (4) reconstruction artery clamped and opened, the distal portion of the internal for recurrent stenosis with resection of the carotid bifurcation shunt is placed into the internal carotid artery. A clamp is placed and grafting.
  • 8. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 8 a b the endarterectomy at the point where the plaque is bulkiest. At this point, the medial fibers are usually gone, but as the dissection continues both proximally and distally, more normal medial tissue may be seen. It is important to develop the dissection plane between the intima and the media if possible because doing so permits the creation of a feathered end point distally as dissection proceeds into a relatively normal portion of the internal carotid artery [see Figure 12]. If the dissection plane is between the media and the adventitia, a feathered end point is much harder to achieve. Failure to achieve a feathered end point often results in a sharp shelf at the internal carotid artery level, which increases the risk of subsequent intimal dissection when blood flow is restored. Once the dissection plane is complete on one side of the arteri- otomy at the level of the common carotid artery, a right-angle clamp is gently inserted into the plane and advanced through it to the opposite side of the arteriotomy, thereby separating the plaque from the arterial wall around the entire circumference of the ves- sel. The clamp is then gently spread and brought downward to complete the circumferential dissection of the plaque proximally. The proximal end point of plaque dissection is obtained by cutting the intima with a No. 15 blade. With the same depth of dissection now existing on both sides of the open common carotid artery, dissection then continues distal- ly up to the carotid bifurcation. At this point, the plaque within the external carotid artery is carefully separated in a circumferential fashion. This is usually done by using a sharp mosquito clamp until all of the plaque has been separated from the vessel wall and dissection has reached normal intima. The freed plaque is gently Figure 10 Carotid arterial procedures. Shown is the technique of grasped with the opened mosquito clamp, traction is applied, and shunt placement, first distally (a) and then proximally (b). a b Open Carotid Endarterectomy Once the carotid bifurcation has been fully mobilized both prox- imal and distal to the lesion, systemic anticoagulation with heparin is initiated. I generally give 5,000 units, an amount that is sufficient to produce adequate anticoagulation for the duration of carotid clamp- ing but is not large enough to necessitate heparin reversal on comple- tion of the operation. If the patient has been receiving clopidogrel— particularly if clopidogrel was given in combination with aspirin— the heparin dose must be reduced to allow adequate hemostasis to be achieved after reconstruction. In these cases, I usually limit the heparin dose to 3,000 units. If internal carotid artery back-pressure is to be used to determine whether the patient requires an internal shunt, then it is measured at this time. If cerebral electrical activity is to be the determinant, then the internal, external, and common carotid arteries are clamped and electrical activity is monitored (e.g., via EEG) with the clamps in place. If electrical changes are noted with clamping, an internal shunt is required. Arteriotomy The common carotid artery and the carotid bifurcation are rotated so as to be positioned for an arteriotomy that begins on the common carotid artery and extends through the bulb of the internal carotid artery to a point 180° opposite the flow divider [see Figure 11]. This incision effectively bivalves the carotid bulb, thus making possible a more accurate primary or patch closure. The arteriotomy continues through the plaque and extends well up into the internal carotid artery, beyond the visible end point of the atherosclerotic plaque. Figure 11 Carotid arterial procedures: open endarterectomy. Clamps are applied to the common, internal, and external Plaque removal A dissection plane separating the athero- carotid arteries, and the structures are rotated (a) so that an sclerotic intima from the media and the adventitia is then devel- arteriotomy can be made in the common carotid artery 180° oped with a sharp-bladed dissector. As a rule, it is easiest to begin opposite the flow divider (b).
  • 9. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 9 a b c Right Wrong Dissection Dissection Plane Plane Intima Adventitia Media Internal External Elastic Elastic Lamina Lamina Figure 12 Carotid arterial procedures: open endarterectomy. (a) Dissection is started where plaque is thickest. Often, medial fibers are completely gone here. Dissection proceeds both proximally and distally along one side, and more normal medial tissue may be found. Development of a plane between intima and media, if possible, is valuable for creating a feathered end point distally. (b) Once dissection is complete on one side, the same plane is established on the opposite side. (c) The end point of proximal dissection is established by sharp division of plaque against the clamp. the distal end point of plaque dissection in the external carotid ed to confirm that all overlying dissected intima has been cleared. artery is obtained. Any residual dissected intima can be gently teased out with a mos- Dissection then continues up the internal carotid artery, with quito clamp. Once the vessel is completely clear, preparation is care taken to leave normal intima behind. Often, the plaque made for closure of the arteriotomy. becomes a relatively narrow tongue of atheroma on the posterior wall of the internal carotid artery. If the edge of the atheromatous Closure of arteriotomy If the arteriotomy is relatively short plaque is followed to its end, a tapered, feathered end point can be and extends only up to the central portion of the bulb of the inter- achieved. nal carotid artery, it can usually be closed primarily with a contin- uous 6-0 polypropylene suture. Placing very small stitches close Irrigation and clearing of debris After removal of the spec- together in the internal carotid artery should minimize the risk of imen, the intimectomized surface is vigorously irrigated with vessel narrowing. heparinized saline. Any medial debris present is carefully removed. If the vessel is relatively small or the arteriotomy was extended The distal end point is irrigated to determine whether there is a well up on the internal carotid artery to ensure a complete residual flap that might lead to subsequent intimal dissection; if endarterectomy, the arteriotomy should be closed with a patch there is a flap, it is carefully removed. If there is a sharp shelf at the angioplasty. Of the several patch options available, the basic choice distal end point, it is usually an indication that the endarterectomy is between a prosthetic patch and an autogenous patch composed has not been carried far enough distally.When this is the case, the of a segment of saphenous vein obtained from an extremity. The arteriotomy should be lengthened so that the endarterectomy can relative merits of autogenous and prosthetic patches have been be extended to a point where the intima is completely normal. If extensively debated in the literature, but no definitive conclusions the patient has a very high carotid bifurcation, very distal plaque, have been reached. One of the disadvantages of an autogenous or both and further dissection is impeded by the base of the skull, patch is that surgeons tend to use the entire open portion of the it may be necessary to secure the distal end point with tacking saphenous vein, which then dilates further under arterial pressure, sutures. Tacking sutures should be used only in exceptional cir- leading to an artery of aneurysmal proportions. Another disadvan- cumstances because their use may lead to healing abnormalities or tage is the potential for patch blowout, which, though rare, has to the presence of platelet aggregate material that can cause throm- been reported in several series. The main disadvantage of a pros- boembolic or occlusive complications. thetic patch is the risk of infection, but this is extremely low. Once the intimectomized surface is completely clear of debris, At present, it would appear that a prosthetic patch is at least as the lumen of the external carotid artery should be visually inspect- acceptable as an autogenous patch, and the prosthetic patch has
  • 10. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 10 a b d c Line of Division Artery Everted Plaque Figure 13 Carotid arterial procedures: eversion endarterectomy. (a, b) The internal carotid artery is divided from the common carotid artery in an oblique line. (c) The divided internal carotid artery is everted on itself so that it can be separated from the underlying plaque. Eversion proceeds distally until the plaque end point is encountered, and the plaque is removed from the internal carotid artery. Proximal endarterectomy of the common carotid artery and endarterectomy of the external carotid artery are then carried out. (d) Once all of the plaque has been removed, the internal carotid artery is reverted and an end-to-side anastomosis is fashioned between the common carotid artery opening and the internal carotid artery. an additional advantage in that there is no need to remove a nor- sponge. If any obvious defect is noted between sutures, an addi- mal saphenous vein segment from an extremity. Prosthetic patch- tional stitch should be placed. es can be composed of either fabric or polytetrafluoroethylene (PTFE). Fabric patches now come impregnated with either colla- Eversion Endarterectomy gen or gelatin to make them leakproof; PTFE patches do not leak Eversion endarterectomy was designed and developed to elim- on the surface, but they are prone to leakage at suture needle inate the need for a suture line on the internal carotid artery, in the puncture sites. hope that doing so would reduce the incidence of myointimal Patch size is a crucial consideration: it is important that the hyperplasia and consequent restenosis. There is evidence to sug- patch be neither too wide nor too narrow. If the patch is too nar- gest that the use of eversion endarterectomy has led to some row, it will not provide the additional material needed to restore reduction in the incidence of myointimal hyperplasia, but the data the carotid bifurcation to a normal diameter. If the patch is too are controversial and certainly are not conclusive. Nonetheless, the wide, it will provide too much additional material and create what technique may well have merit, and it should be a part of the vas- virtually amounts to a carotid aneurysm; this would represent a cular surgeon’s armamentarium. significant disadvantage to the patient in terms of flow dynamics Besides the avoidance of a suture line on the internal carotid and the risk of producing laminated thrombus in the most dilated artery, the advantages of eversion endarterectomy include the sim- portion of the carotid bulb. My preference is to use a 6.0 mm wide ple end-to-side anastomotic closure and the possibility of manag- collagen-impregnated fabric patch for patch angioplasty. ing a redundant internal carotid artery by moving it down the com- Whichever patch is selected is cut to length, beveled at each end, mon carotid artery. One disadvantage is the potential difficulty of and sewn in place with a continuous 6-0 polypropylene suture. achieving an end point in cases in which the bifurcation is high or Before completion of the closure, the internal carotid artery and plaque extends well up the internal carotid artery toward the base the external carotid artery are back-bled and the common carotid of the skull. Another disadvantage arises with patients who require artery flushed. The arteriotomy is then completely closed. an internal shunt, in that it is not possible to keep an internal shunt Removing the clamp on the internal carotid artery allows blood in place for the entire duration of an eversion endarterectomy.Yet flow to fill the carotid bulb and permits one last internal flush.The another disadvantage is that the distal end point cannot be viewed origin of the internal carotid artery is then occluded with a vascu- as clearly as it can in open endarterectomy. A fourth disadvantage lar forceps, and the clamps are removed first from the external is that eversion endarterectomy is poorly suited to cases in which carotid artery and then from the common carotid artery to allow the internal carotid artery is relatively small and contracted and resumption of blood flow. After several heartbeats, the forceps on thus better treated with patch angioplasty. the origin of the internal carotid artery is removed, and blood flow through the internal carotid artery is restored.There may be some Eversion and plaque dissection After the carotid bifurca- leakage of blood along the suture line, which can usually be con- tion is fully mobilized, the internal, external, and common carotid trolled with the placement of thrombin-soaked absorbable gelatin arteries are clamped. A circumferential incision is placed in an
  • 11. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 11 oblique fashion at the junction of the common carotid artery and carotid artery. The vagus nerve is identified and carefully protect- the bulb of the internal carotid artery to permit division of the bul- ed. The common carotid artery is then mobilized both proximally bous portion of the internal carotid artery from the common and distally; proximal mobilization should extend as far behind the carotid [see Figure 13].The edges of the adventitia of the bulb of the sternoclavicular junction as the surgeon can comfortably manage. internal carotid artery are grasped, and the outer layers of the ves- sel wall are gradually everted away from the plaque within the Transection and anastomosis The common carotid artery artery. Eversion continues cephalad until it reaches the distal end is clamped proximally and distally, then divided; the proximal por- point of the atherosclerotic lesion, which is marked by the presence tion of the vessel is oversewn. The transected common carotid of a thin, filmy intima that clearly separates with the specimen, leav- artery is brought posterior to the jugular vein in the vicinity of the ing normal vessel behind.The plaque in the common carotid artery subclavian artery. The subclavian artery is clamped proximally and the external carotid artery is then removed in the traditional and distally, a longitudinal arteriotomy is made, and a small ellipse manner; the opening in the common carotid artery may be ex- of subclavian arterial tissue is removed. The end of the common tended proximally to facilitate this portion of the endarterectomy. carotid artery is then sewn to the side of the subclavian artery with a continuous 6-0 polypropylene suture. Reversion and reanastomosis The internal carotid artery Before completion, the vessels are back-bled and flushed. Once is then reverted to its normal anatomic position, and an anasto- the anastomosis is complete, blood flow is restored, first to the dis- mosis between the end of the divided bulb of the internal carotid tal subclavian artery and then to the common carotid artery. artery and the common carotid artery is fashioned with a contin- uous 6-0 polypropylene suture. If the internal carotid artery is Reconstruction for Recurrent Carotid Stenosis redundant [see Special Considerations, below], the arteriotomy on For an initial recurrence of carotid stenosis that primarily the common carotid artery is extended proximally and the arteri- results from myointimal hyperplasia, conversion to a patch angio- otomy on the medial aspect of the bulb of the internal carotid plasty is generally the best treatment. For second or third recur- artery is extended distally so that the carotid bifurcation may be rences or for recurrences that develop in spite of patch angioplas- advanced between the internal and common carotid arteries to ty, resection of the carotid bifurcation with interposition grafting eliminate the redundancy. between the common carotid artery and the normal distal inter- nal carotid artery is the best treatment. Reconstruction for Proximal Lesions of Common Carotid Artery Exposure and mobilization Exposure of a carotid bifur- Lesions at the origin of the common carotid artery, either at the cation for treatment of recurrent carotid stenosis can be chal- level of the aortic arch (in the case of the left common carotid lenging. The initial skin incision is reopened, and dissection is artery) or at the innominate bifurcation (in the case of the right carried down through the scar tissue to the common carotid common carotid artery), are relatively rare but do occur. Such artery. The common carotid artery is sharply dissected from the lesions may arise either in isolation or in combination with carotid surrounding scar tissue, with the dissection plane kept close to bifurcation disease. They can be managed by dividing the com- the adventitia to minimize the risk of injury to the vagus nerve mon carotid artery and transposing it to the adjacent subclavian and the hypoglossal nerve. Once the common carotid artery has artery, provided that there is no occlusive disease in the ipsilateral been adequately mobilized, dissection is carried distally to subclavian artery. include the carotid bifurcation and the internal carotid artery. In the course of distal dissection, care must be taken to watch for Exposure and mobilization If the lesion at the origin of the the hypoglossal nerve, which may be incorporated into the scar common carotid artery is the only one being treated, both the tissue; this structure must be carefully dissected away from the common carotid artery and the subclavian artery should be artery and protected. exposed through a supraclavicular incision that parallels the clav- Distal dissection continues beyond the end point of the previ- icle. If a carotid bifurcation lesion is present in conjunction with ous closure of the internal carotid artery. Beyond this end point, the lesion at the origin of the common carotid artery, the supra- it is usually possible to enter a previously undissected plane of the clavicular incision is supplemented with a vertical incision along internal carotid artery; from here onward, the artery typically is the sternocleidomastoid muscle to permit exposure of the carotid soft around its circumference and is not involved in the recurrent bifurcation. Exposure of the bifurcation has already been stenosis. The external carotid artery is then mobilized sufficiently addressed (see above); accordingly, I focus here on exposure of the to allow the surgeon to control back-bleeding. subclavian artery and the proximal common carotid artery. A supraclavicular incision is placed approximately 1.5 finger- Conversion to patch angioplasty If the artery was origi- breadths above the clavicle and centered over the lateral head of nally closed primarily, an arteriotomy is made through the old the sternocleidomastoid muscle. The lateral head of the stern- suture line and carried distally through the area of stenosis and ocleidomastoid muscle is divided, and the scalene triangle is onto a relatively normal area of the internal carotid artery. defined. The scalene fat pad is mobilized off the anterior scalene Exploration of the luminal surface usually reveals a smooth, glis- muscle. The phrenic nerve is identified, mobilized off the scalene tening neointima, and observation of the cut section of the artery muscle, and gently retracted. A plane is developed with gentle dis- reveals an area where a whitish, firm thickening of the intimal wall section between the posterior portion of the anterior scalene mus- has occurred as a result of myointimal hyperplasia. No attempt cle and the underlying subclavian artery, and the anterior scalene should be made to reendarterectomize the stenotic area, because muscle is divided. Division of the muscle exposes the underlying the intimal lesion is not, in fact, plaque but scar tissue. If the inti- subclavian artery, a sufficient length of which can then be mobi- ma is removed, the cascade of events that led to the myointimal lized in the perivascular plane to permit an anastomosis. hyperplasia will simply be reinitiated. Accordingly, the healed inti- The jugular vein is identified at the medial aspect of the incision mal surface should be carefully protected. A patch angioplasty and mobilized anteriorly and medially to expose the common across the stenotic area, extending from the common carotid
  • 12. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 12 artery proximally to a relatively normal portion of the internal carotid artery distally, is usually sufficient to treat the lesion. Resection of carotid bifurcation with interposition graft- ing If the stenosis is recurring for the second or third time or the artery was originally closed with a patch, the surgeon should pro- ceed with resection and interposition grafting. In most cases, it is necessary to sacrifice the external carotid artery and oversew its origin. The internal carotid artery is divided distal to the intimal hyperplastic lesion, the common carotid artery is divided proxi- mally, and the diseased specimen is removed. I prefer to use 6.0 mm thin-walled PTFE for the interposition graft.The internal carotid artery distally and the common carotid Figure 14 Carotid arterial artery proximally are spatulated by making vertical incisions procedures: repair of fibro- approximately 6.0 mm in length.The PTFE graft is appropriately muscular dysplasia. Depicted beveled both proximally and distally, and beveled or spatulated is the so-called string of beads end-to-end anastomoses are performed, first to the internal deformity of the cervical por- carotid artery and then to the common carotid artery. tion of the internal carotid Before completion, the vessels are back-bled and flushed; once artery, which is characteristic the anastomoses are complete, blood flow is reestablished. of medial fibroplasia. Some surgeons may be tempted to use autogenous saphenous vein for the interposition graft. To use such grafts would appear, on the face of it, to be a good idea; in fact, it is a mistake. For rea- In symptomatic patients with fibromuscular dysplasia, the sons not clearly understood, the use of autogenous saphenous vein carotid bifurcation may be exposed in the usual manner. If there in the neck has an extremely poor track record, yielding unaccept- is significant redundancy of the internal carotid artery, as docu- ably high rates of recurrent stenosis and occlusion in comparison mented by preoperative imaging, the artery should be mobilized with the use of prosthetic grafts. relatively extensively so that it can be straightened by downward traction before intraluminal dilatation is begun. If, on the other Special Considerations hand, the artery is relatively straight, only minimal mobilization is Fibromuscular dysplasia of internal carotid artery required. It should be kept in mind that approximately 25% of Fibromuscular dysplasia of the internal carotid artery is a congeni- patients with fibromuscular dysplasia have associated atheroma- tal or acquired lesion that has been subdivided into four pathologic tous disease of the carotid bifurcation that must be dealt with at varieties, of which the most common is medial fibroplasia. On con- the time of operation. In addition, about the same number of trast angiography, medial fibroplasia has a characteristic appear- ance, resembling a string of beads in the extracranial portion of the a internal carotid artery [see Figure 14]. A common initial manifesta- tion is a relatively loud bruit in the neck of a young woman. b Fibromuscular dysplasia can cause symptoms of monocular or hemispheric TIAs, or it may go on to cause a stroke, usually as a consequence of a dissection resulting in thrombotic occlusion. If symptoms develop, they can generally be controlled by means of antiplatelet drugs. Currently, the only indication for surgical inter- vention is the persistence of symptoms despite antiplatelet therapy. Treatment of fibromuscular dysplasia has evolved over the years.The first attempts at surgical repair involved a total resection of the internal carotid artery coupled with interposition of a graft (usually composed of saphenous vein). This technique has largely been abandoned because of the extensive surgical dissection required and the substantial risk of cranial nerve injury; its only remaining application is in cases where there is associated aneurysmal dilatation in the dysplastic segment that calls for resec- tion and graft interposition. At present, the two most popular modes of therapy both involve intraluminal dilatation with disrup- tion of the small septa within the artery. One mode achieves intra- luminal dilatation via an open approach, and the other achieves the same end via a percutaneous approach that includes balloon angioplasty. Dilatation and fracturing of the intraluminal septa Figure 15 Carotid arterial procedures: repair of fibromuscular often result in the release of particles of septal tissue, which in turn dysplasia. (a) The proximal portion of the internal carotid bulb is can lead to cerebral embolization and infarction. Consequently, an clamped, a transverse arteriotomy is made, and a coronary dilator open approach, which enables the surgeon to flush out the dis- is passed into the internal carotid artery and advanced up the ves- rupted segments, or balloon angioplasty with cerebral embolic pro- sel to the base of the skull. (b) The small septa in the internal tection is usually favored. carotid artery are disrupted by the advancing probe.
  • 13. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 13 a b c a patch angioplasty. Provided that the arteriotomy extends beyond the apex of the kink, the patch should smooth out the curvature of the redundant vessel and eliminate the kink. If it appears that inter- nal carotid artery redundancy is greater than can be corrected by an elongated patch, then detachment of the internal carotid artery followed by eversion endarterectomy and reimplantation is indicated. If the arteriotomy has already been closed when it becomes apparent that a kink is present, the problem may be dealt with by mobilizing the external carotid artery sufficiently and then resect- ing a segment of the common carotid artery and pulling down on the carotid bifurcation with a new end-to-end anastomosis to straighten the redundant internal carotid artery [see Figure 17]. Segmental resection of the internal carotid artery itself combined with end-to-end repair has also been described; this approach is less desirable, being more technically demanding and hence more subject to technical error. Patients with coiling of the internal carotid artery may present a more difficult problem. If the atheromatous plaque involves only the first portion of the internal carotid artery and the vessel Figure 16 Carotid arterial procedures: repair of coiling or kink- beyond that first portion is relatively normal up to the point where ing of the internal carotid artery. (a, b) Redundancy of the inter- coiling begins, the surgeon can simply avoid the problem by leav- nal carotid artery can result in one or more 360º coils in the ves- ing the smooth coil in place and not carrying out an extensive dis- sel. (c) Degenerative atheromatous changes of the internal carotid tal dissection. If, on the other hand, it appears that there may be artery can cause elongation with associated kinking or buckling. plaque in the coil, then the entire coil must be dissected free, and the patient is left with a very redundant internal carotid artery that must be dealt with. Once again, the best method of managing the patients have associated intracranial aneurysms that should be problem is to resect the redundant segment of the internal carotid checked for by means of intracranial imaging studies. artery, with or without eversion endarterectomy, and to reimplant Once the carotid bifurcation has been suitably mobilized and it the internal carotid artery onto the distal common carotid artery has been established that no associated atheromatous plaque is at the point of transection. present, a small transverse incision is made on the bulb of the internal carotid artery, with flow being maintained between the common and external carotid arteries. Serial intraluminal dilata- tions are then performed with coronary artery dilators of progres- sively increasing diameter [see Figure 15].The first dilator (usually a b 2.5 mm in diameter) is passed up the carotid artery to the base of the skull under digital control.The dilator is then withdrawn, and the artery is back-bled to flush out any fractured segments. The next larger dilator (3.0 mm in diameter) is passed in a similar fash- ion. Dilatation is repeated with progressively larger dilators (3.5, 4.0, and possibly 4.5 mm in diameter) to complete the procedure. The transverse arteriotomy is closed with 6-0 polypropylene suture material and flow is reestablished. A completion angiogram verifies that the dysplastic segment is fully restored. Coiling or kinking of internal carotid artery Redun- dancy of the internal carotid artery, often resulting in a 360° coil of the high cervical portion of the internal carotid artery, is usual- ly thought to be developmental in origin [see Figure 16a]. Elon- gation of the internal carotid artery, which often results in kinking of the vessel, is believed to be related to the degenerative changes that occur with aging and atherosclerosis [see Figure 16b]. Both of these phenomena, in and of themselves, are usually asymptomatic; exceptions occur when an atheromatous plaque develops at the apex of the coil or when kinking of the internal carotid artery is accentuated with changes in head position in a patient who depends on relatively normal blood flow through that vessel. Redundancy of the internal carotid artery often becomes a tech- Figure 17 Carotid arterial procedures: repair of coiling or kinking nical consideration during standard surgical treatment of a carotid of the internal carotid artery. Kinking or redundancy of the inter- bifurcation atheroma.When redundancy occurs, it must be appro- nal carotid artery can be managed by mobilizing the external priately dealt with to prevent postoperative complications. carotid artery, then resecting a segment of the common carotid Anticipated redundancy of the internal carotid artery at the time artery (a). The surgeon can then draw down the carotid bifurcation of carotid bifurcation endarterectomy can usually be managed with for a new primary anastomosis (b).
  • 14. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 14 Upon completion of the reconstruction, a completion angio- the equipment. Standard B-mode imaging, in conjunction with gram should be obtained to verify that the coiling or kinking has Doppler ultrasonography, can accurately identify patent or com- been adequately treated. promised internal and external carotid arteries. Once the surgeon has confirmed that a good technical recon- STEP 5: COMPLETION IMAGING struction has been achieved, preparations can be made for closure. Given that the majority of neurologic complications after STEP 6: CLOSURE carotid artery surgery are attributable to technical error, it is imperative that the technical accuracy of the reconstruction be The dissected area around the reconstructed carotid artery is confirmed before the incision is closed and the patient is sent to carefully irrigated with an antibiotic solution, and the wound is the recovery room. There are two principal methods of determin- meticulously inspected for hemostasis. Even when good hemosta- ing the technical quality of the reconstruction: on-table angiogra- sis has been achieved, it is my practice to place a drain overnight— phy and direct-contact duplex scanning of the carotid artery. To specifically, a 7.0 mm Jackson-Pratt drain brought out through a perform either of these techniques routinely in all patients adds small separate stab wound. The platysmal layer is closed with a relatively little time to the surgical procedure and offers significant continuous 3-0 absorbable suture, and the skin is closed with a advantages to both the patient and the surgeon.11,12 continuous 4-0 subcuticular absorbable suture. A clear adhesive My preferred method of confirming the quality of the recon- plastic dressing is applied to the skin, and the patient is sent to the struction is completion angiography using a C-arm with digital recovery room. imaging. For this reason, the operation is done on a table that has angiographic capability, and the radiology technician and the equipment are called for at the beginning of the arteriotomy clo- Postoperative Care sure. A 10 ml syringe is connected to flexible tubing, and a 20- The main patient variables to be evaluated in the postoperative gauge needle is attached to the end of the tubing and bent at a 45° period are neurologic status, blood pressure, and wound stability. angle. Air bubbles are carefully evacuated from the tubing and the On awakening from anesthesia, the patient is carefully observed needle. Placing the needle into the artery or, in the case of a with a view to determining gross cerebral function on the basis of patched artery, into the midportion of the patch in a retrograde response to commands and movement of extremities. When the fashion will provide good stability for the needle, which lies in the patient is fully awake, vagus nerve and hypoglossal nerve function lumen of the artery in an axial position. Once the C-arm is in place can be tested. and the fluoroscopy unit turned on, the contrast material is inject- Blood pressure monitoring is of critical importance after CEA. ed by hand. The resulting image of the carotid bifurcation can be It is essential first to decide on an acceptable blood pressure range continuously replayed until maximal radiographic opacity of the for the patient and then to ensure that this pressure is maintained: carotid bifurcation and the intracranial circulation has been neither hypertension nor hypotension is acceptable. Patients with attained. The image is then carefully inspected for defects at the severe carotid bifurcation disease who have undergone CEA tem- end points in the internal and external carotid arteries. porarily lose autoregulation on the side of the operation; therefore, Intimal defects in the internal carotid artery are unusual, hypertension can result in reperfusion injury to that side of the though not rare. Defects in the external carotid artery are more brain, ranging all the way from simple headache to fatal intracere- common because the endarterectomy is essentially done in a blind bral hemorrhage. or closed manner. Defects in the external carotid artery are mat- The surgical site should be carefully observed for possible ters of concern because they may lead to thrombus formation in wound expansion resulting from hematoma formation. Even this vessel; if the thrombus propagates proximally, it may embolize when good hemostasis is achieved and a drain is in place, there is up the internal carotid artery and cause a stroke.13 For this reason, still the possibility of delayed bleeding leading to hematoma and if a defect is found in the external carotid artery, it is repaired at airway compromise. If an expanding hematoma is noted, the safest the time of the operation. To accomplish the repair, clamps are response is to return the patient to the OR so that the hematoma placed on the external carotid artery proximally at its origin and can be evacuated and a bleeding site sought. The earlier this is distally beyond the intimal flap. A transverse arteriotomy is made done, the better. in the external carotid artery to permit identification and removal If the patient is neurologically intact, blood pressure is well con- of the intimal flap. Once the flap has been carefully removed, the trolled, and there is no evidence of an expanding hematoma, then transverse arteriotomy is closed with two or three interrupted 6-0 the remaining postoperative care can be provided in a regular hos- polypropylene sutures and flow is restored. pital room. It is seldom necessary to observe the patient in the Completion angiography also has the advantage of permitting intensive care unit, as was once standard practice. the surgeon to image the intracranial circulation. Now that many operations are being performed on the basis of preoperative carotid duplex scanning, intracranial imaging is typically unavail- Follow-up able beforehand, which means that the status of the intracranial Periodic follow-up examination is essential.There are two major circulation with respect to atherosclerotic lesions in the area of the areas of concern: (1) the possibility of recurrent stenosis on the side siphon or the middle cerebral artery or with respect to intracranial that was operated on and (2) the possibility of disease developing or aneurysms is usually unknown at the start of the procedure. A progressing in the contralateral carotid artery. It is my practice to completion angiogram gives the surgeon the opportunity to rule see the patient approximately 3 weeks after CEA. In that visit, the out these lesions by looking not only at the area around the recon- patient is examined for quality of wound healing and the presence struction but also at the intracranial circulation. or absence of a carotid bruit on both the operated side and the con- An alternative to completion angiography is intraoperative tralateral side, and a carotid duplex scan is performed. If at this time DUS. DUS can be a highly satisfactory way of examining the area there are no grounds for concern about the contralateral side, scan- of reconstruction, provided that the operating room has duplex ning is done only on the side of the operation. The scan serves to scanning capability and that a technologist is available to operate establish the new baseline and confirms that the carotid reconstruc-
  • 15. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 9 SURGICAL TREATMENT OF CAROTID ARTERY DISEASE — 15 tion is satisfactory. The new baseline is then used as the basis for istry, but the important part of the study was a randomized, mul- assessing patient status during subsequent follow-up. ticenter trial involving 307 patients at 29 investigational sites. Of The next patient visit takes place 6 months after operation, at these 307 patients, 156 were entered into the CAS–cerebral pro- which time a bilateral carotid duplex scan is performed. If the oper- tection arm and 151 into the CEA arm. The primary end points ated side continues to be normal and there are no major problems were (1) death, any stroke, or nonfatal myocardial infarction (MI) on the contralateral side, the patient is seen again at the 1-year within 30 days after the procedure and (2) 30-day major morbidi- anniversary of the procedure. If examinations yield satisfactory ty plus death and ipsilateral stroke between 31 days and 12 months results at this time, the patient may thereafter be seen at 1-year after the procedure. Secondary end points included (1) patency intervals, with bilateral carotid duplex scanning done at each visit. (defined by restenosis < 50%), (2) disabling stroke between 30 days and 6 months, and (3) a composite of major adverse clinical events at 6 months, 1 year, 2 years, and 3 years. Alternatives to Direct Carotid Reconstruction At 30 days, there were no statistically significant differences Carotid angioplasty with stenting (CAS) has been investigated between the two study arms when the individual parameters— as a therapeutic alternative to CEA for carotid artery stenosis [see death, stroke, and nonfatal MI—were considered separately. 6:10 Carotid Angioplasty and Stenting]. In the Wallstent trial (an When these events were viewed in the aggregate, their composite industry-supported prospective, randomized study), patients with incidence was 5.8% in the CAS–cerebral protection group and stenosis of 60% to 99%, which was angiographically confirmed 12.6% in the CEA group.When death and stroke were considered according to the North American method of measurement, were together, however, the incidence was 4.5% in the CAS–cerebral randomly assigned to undergo either CAS or CEA.14 Initially, it protection group and 6.6% in the CEA group. Thus, it is appar- was proposed that the study would include 700 patients with ent that the major benefit of CAS over CEA lies in reducing the symptomatic lesions; however, the trial was stopped by the safety- incidence of nonfatal MI. monitoring committee after 219 patients were randomized. The In November 2006, the results of a large French trial that com- results were reported at the 26th International Stroke Conference pared CAS with CEA in good-risk symptomatic patients were pub- in February 2001. lished.16 The study design called for the prospective randomiza- Of the 219 patients, 107 were entered into the CAS arm and tion of 872 patients so as to yield a statistical power of 80%, the 112 into the CEA arm. Patients were well matched with respect to aim being to determine whether CAS was not inferior to CEA. age, gender, symptoms, degree of stenosis, and median follow-up. After the inclusion of 527 patients, the trial was stopped prema- The primary end point was ipsilateral stroke, procedure-related turely for reasons of unsafety and futility.The 30-day incidence of death, or vascular death within 1 year. At approximately 1 year, the any stroke or death was 3.9% after CEA and 9.6% after CAS. At primary end-point rate was 12.1% in the CAS group and 3.6% in 6 months, the incidence of stroke or death was 6.1% after CEA the CEA group. The 30-day stroke morbidity and mortality was and 11.7% after CAS.16 12.1% in the CAS group and 4.5% in the CEA group. Upon ces- On the basis of the evidence accumulated to date, the Medicare sation of the study, the investigators concluded that CAS was not guidelines are still appropriate. CAS is indicated only for (1) equivalent to CEA for treatment of symptomatic carotid stenosis. symptomatic patients in whom CEA, in the opinion of a vascular In the SAPPHIRE (Stenting and Angioplasty with Protection in surgeon, poses unacceptable risks or (2) patients who are willing Patients at High-Risk for Endarterectomy) trial, which was also an to participate in an approved clinical trial (e.g., CREST [Carotid industry-sponsored study, CAS with the use of a cerebral antiem- Revascularization Endarterectomy versus Stenting Trial]). CEA bolism device was compared with CEA.15 Nonrandomized remains the treatment of choice for patients with suitable lesions patients were entered into either a stent registry or a surgical reg- of the carotid bifurcation. References 1. Beneficial effect of carotid endarterectomy in 6. Asymptomatic Carotid Surgery Trial struction: a valuable tool. J Vasc Surg 7:260, 1988 symptomatic patients with high-grade carotid Collaborators. The MRC Asymptomatic Carotid 13. Moore WS, Martello JY, Quiñones-Baldrich WJ, et stenosis. North American Symptomatic Carotid Surgery Trial (ACST). Carotid endarterectomy al: Etiologic importance of the intimal flap of the Endarterectomy Trial Collaborators. N Engl J Med prevents disabling and failed carotid territory external carotid artery in the development of post- 325:445, 1991 strokes. Lancet 363:1491, 2004 carotid endarterectomy stroke. Stroke 21:1497, 2. MRC European Carotid Surgery Trial: interim 7. Moore WS, Barnett HJM, Beebe HG, et al: 1990 results for symptomatic patients with severe (70- Guidelines for carotid endarterectomy—a multi- disciplinary consensus statement from the Ad Hoc 14. Alberts MJ: Results of a multicenter prospective 99%) or with mild (0-29%) carotid stenosis. randomized trial of carotid artery stenting vs. European Carotid Trialists’ Collaborative Group. Committee, American Heart Association. Circulation 91:566, 1995 carotid endarterectomy (abstr). Stroke 32:325d, Lancet 337:1235, 1991 2001 3. Mayberg MR, Wilson SE, Yatsu F, et al: Carotid 8. Fisher DF Jr, Clagett GP, Parker JI, et al: Mandibular subluxation for high carotid exposure. 15. Yadav J, for the SAPPHIRE Investigators: Stenting endarterectomy and prevention of cerebral and angioplasty with protection in patients at high ischemia in symptomatic carotid stenosis. Veterans J Vasc Surg 1:727, 1984 risk for endarterectomy: the SAPPHIRE study Affairs Cooperative Studies Program 309 Trialist 9. Moore WS, Yee JM, Hall AD: Collateral cerebral (abstr). Circulation 106:2986a, 2002 Group. JAMA 266:3332, 1991 blood pressure—an index of tolerance to tempo- rary carotid occlusion. Arch Surg 106:520, 1973 16. Mas J-L, Chantellier G, Beyssen B, et al: 4. Endarterectomy for asymptomatic carotid artery Endarterectomy versus stenting in patients with stenosis. Executive Committee for the 10. Moore WS, Hall AD. Carotid artery back pres- sure—a test of cerebral tolerance to temporary symptomatic severe carotid stenosis. N Engl J Med Asymptomatic Carotid Atherosclerosis Study. carotid occlusion. Arch Surg 99:702, 1969 355:1660, 2006 JAMA 273:1421, 1995 5. Hobson RW II, Weiss DG, Fields WS, et al: 11. Blaisdell FW, Lim R Jr, Hall AD: Technical results Efficacy of carotid endarterectomy for asympto- of carotid endarterectomy: arteriographic assess- matic carotid stenosis. The Veterans Affairs ment. Am J Surg 114:239, 1967 Acknowledgment Asymptomatic Cooperative Study Group. N Engl 12. Schwartz RA, Peterson GJ, Noland KA, et al: J Med 328:221, 1993 Intraoperative duplex scanning after carotid recon- Figures 1 through 17 Tom Moore.