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UCLA » UCLA Healthcare » UCLA Neurology » Stroke Center » Brain Attack Newsletter: October 1999 |  |
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October 1999
Update Volume 1, Issue Number 1 Carotid Endarterectomy: 1999 UpdateNeil A. Martin, MD, Professor, Neurosurgery Since Cooley,Al-Maaman, and Carton first reported the performance of a successfulcarotid endarterectomy in the Journal of Neurosurgery in 1956, therehas been a substantial evolution in our knowledge of carotidatherosclerosis and carotid endarterectomy. Symptomatic carotidatherosclerosis: The European Carotid Surgery Trial (ECST, Lancet,1991), and the North American Symptomatic Carotid Endarterectomy Trial(NASCET, NEJM, 1991) conclusively demonstrated that carotidendarterectomy was superior to medical care (antiplatelet therapy)alone for patients with retinal or hemisphere ischemic symptoms due tosevere carotid stenosis. While different methods were used to estimatethe degree of stenosis in the two trials, "severe stenosis" is nowgenerally considered to consist of a carotid lumen diameter reductionof 70% or more. In NASCET the perioperative morbidity and mortalityrate for the surgical group was 5.8%. The risk for ipsilateral strokeat 2 years after entry into the trial was 9% for patients undergoingendarterectomy; and 26% for patients treated without surgery. In afollow-up study, the NASCET collaborators reported on the benefit ofcarotid endarterectomy among patients with stenosis of 50-69%. In thisgroup the 5 year rate of ipsilateral stroke was 16% in patients treatedsurgically, and 22.2% in patients treated medically. In patients withless than 50% stenosis, there was not a significant difference betweenthe patients treated surgically and those treated medically. Thebenefit associated with carotid endarterectomy for moderate stenosiswas greatest in men, in those with recent mild stroke as opposed toTIA, and in patients with hemispheric (as opposed to retinal) symptoms. Asymptomatic carotidstenosis: In 1995 the results of the Asymptomatic CarotidAtherosclerosis Study (ACAS) were published in the Journal of theAmerican Medical Association (JAMA). This study lent substantialsupport to the strategy of performing endarterectomy, for strokeprevention, in asymptomatic patients with significant stenosis(>60%). In this randomized clinical trial, the surgical group had a5.1% risk of ipsilateral stroke ( or perioperative morbidity) after 5years. The medical group had an 11% risk for stroke after 5 years. Over5 years, therefore, surgery reduced absolute risk by 5.9% and relativerisk by 53%. The absolute risk reduction annually, therefore, for thegroup as a whole was only about 1%. The benefits of endarterectomy forasymptomatic stenosis were greatest in patients under the age of 67,and in men. This study lead aspecial writing group of the Stroke Council of the American HeartAssociation in a consensus statement entitled, "Guidelines for CarotidEndarterectomy" to incorporate these findings in their recommendationsfor the treatment of asymptomatic patients with carotid stenosis ofgreater than 60%. However, others have pointed out that the magnitudeof risk reduction in this trial, while statistically significant, mayhave marginally clinical significance. Other studies have suggestedthat the benefit associated with endarterectomy for asymptomaticstenosis is greatest in patients with more severe stenosis (>80%),and have suggested that more selective criteria be employed foridentifying patients to undergo prophylactic endarterectomy. Complication avoidancefor carotid endarterectomy: The benefit of carotid endarterectomy isonly realized if the procedure is completed with a very low rate ofperioperative morbidity and mortality. It is clear that the risk ofcomplications associated with carotid endarterectomy vary widelybetween series', hospitals, and individual surgeons. In order toachieve the beneficial results described in the NASCET and ACASstudies, it is imperative that patients be treated in medical centers,and by surgeons who have comparably low rates of surgical morbidity andmortality.The most important intraoperative surgical complication involvescerebral ischemia during carotid clamping. A number of strategies havebeen used to identify the patients for whom carotid artery shunting isrequired: these include EEG, and transcranial Doppler. Theelectroencephalogram is sensitive to critical changes in cerebralperfusion and is the most effective technique for demonstrating theonset of neuronal dysfunction due to intraoperative ischemia. However,subtle changes may not be appreciated immediately. Transcranial Dopplermonitoring of flow velocity in the ipsilateral middle cerebral arteryprovides real-time quantitative assessment of cerebral hemisphericperfusion. The risk of cerebral ischemia is high when the middlecerebral artery velocity falls to less than 40% of baseline uponcarotid clamping. It is our practice to use EEG and transcranialDoppler in parallel, to provide both functional and hemodynamicassessment of the effects of carotid artery clamping, to providemonitoring redundancy as a "fail-safe" strategy. When either of thesetests demonstrate hemodynamic insufficiency after clamping, a shunt isemployed. Most postoperativecerebral ischemic complications are related to embolization, or delayedthrombosis originating at the endarterectomy site. Meticulousmicrosurgical technique minimizes the risks of these complications, byensuring that atherosclerotic plaque removal is optimal. The most significantlate complication of carotid endarterectomy is recurrent stenosis, dueeither to re-accumulation of atherosclerosis, or neointimalhyperplasia. There is accumulating evidence that the use of a patchgraft to expand the carotid bulb reduces the risk of late carotidstenosis, and it has become our practice to use a synthetic graft inthe majority of patients. In order to be surethat the desired anatomic result has been achieved we routinely performcompletion intraoperative angiography. Results of carotidendarterectomy at UCLA: At UCLA, carotid endarterectomy is performed bysurgeons in both the Divisions of Vascular Surgery and Neurosurgerywith exemplary results comparable to those published in NASCET, andACAS. On the Neurovascular Service, (N. Martin, M.D., J. Frazee, M.D.),there have been no perioperative deaths, and only one disablingperioperative stroke in the last 100 patients undergoing carotidendarterectomy. Conclusion: Recentlypublished evidence from large prospective randomized clinical trialshave definitively established the efficacy of carotid endarterectomyfor stroke prevention in both symptomatic and asymptomatic patients.The benefits of carotid endarterectomy, however, are only realized whencarefully and appropriately selected patients receive a technicallyexcellent endarterectomy. Carotid Angioplasty and StentingSince it was developedby Gruentzig in the early 1970's, balloon angioplasty foratherosclerotic stenoses has achieved wide use. More recently, vascularstents have been employed to maintain the luminal dilatation achievedwith angioplasty, and to reduce the rate of delayed recurrent stenosis.Extracranial carotid angioplasty has been employed in selected casesover the past decade, and clinical trials of angioplasty/stenting forcarotid stenosis, in comparison to carotid endarterectomy, are underwayor planned in both the United Kingdom and North America. However,despite the relative technical ease of carotid angioplasty andstenting, and the recently published encouraging results, a recentconsensus statement from the American Heart Association (and its StrokeCouncil) has emphasized that this procedure cannot yet be consideredcomparable to or a substitute for conventional endarterectomy. Thereare several reasons for this opinion (which was published in severaljournals in early 1998):1. Carotidendarterectomy has been proven, in the trials cited above, to beeffective for the management of symptomatic and asymptomatic carotidatherosclerosis; 2. While carotidangioplasty and stenting are "minimally invasive", carotidendarterectomy is a relatively safe and inexpensive procedure with ausually brief (1-3 day) hospital stay; 3. Before angioplastyand stenting can be considered for general use, the periproceduralmorbidity and mortality rates must be definitively established, and therisk of late recurrent stenosis determined.Carotid angioplasty and stenting may, in carefully selected cases, bethe optimal treatment for non-atherosclerotic causes of carotid arterystenosis such as prior radiation therapy, neointimal hyperplasia afterprior surgery, unstable symptomatic carotid dissection, andfibromuscular hyperplasia. Angioplasty and stenting may also beindicated for atherosclerotic stenoses that are located high above thecarotid bulb, where surgical endarterectomy may be difficult or risky.Carotid and intracranial angioplasty/stenting are performed, for theseindications, by the interventional neuroradiology services at UCLA. The general consensus,at this point in time, is that with certain exceptions, the use ofcarotid angioplasty and stenting should be limited to ongoingcontrolled randomized trials. References Figures courtesy of Pablo Villablanca, MD, UCLA Division of Neuroradiology Fig 2.: Three dimensional volume rendering of CT angiogram seen in Fig. 1. ------------------------------------ UC Regents-UCLA Stroke Center UCLA Stroke Center and Neurovascular Program Event Calendar Monthly Stroke Conference - UCLA physicians and guest faculty address innovative research and clinical issues in stroke4:00 p.m., 2nd Tuesday of the Month Weekly Neurovascular Case Conference - Case reviews, highlighting imaging, neurointerventional neuroradiology, and surgical techniques with multidisciplinary discussion of outcomes and clinical management Call the UCLA Stroke Hotline 24 hours a day (310) 825-6466 for:
UCLA Stroke Center and Neurovascular Overview:The UCLA Stroke Centerand Neurovascular Program offers a comprehensive approach to patientswith cerebrovascular disorders. The Stroke Center/Neurovascular Programprovides coordinated diagnostic and treatment plans for the following:
Patients receiveevaluation and treatment by a multidisciplinary team of specialiststhat include stroke neurologists, vascular neurosurgeons,interventional neuroradiologists, emergency medicine physicians, andrehabilitation physicians, as well as nurses and therapists (seephoto). In the past five years, the UCLA Stroke Center andNeurovascular Program have developed an international referral base.The UCLA Stroke Center and Neurovascular Program have recently beenrecognized in U.S. News and World Report and Time Magazine as centersof excellence and innovation in vascular neurology and neurosurgery. In addition, theseprograms are designed to be responsive to the needs of managed carepayors and referring physicians. As part of UCLA's ClinicalEffectiveness Initiative, we have established clinical pathways andoutcome measurements for acute ischemic stroke, intracranial aneurysm,carotid endarterectomy and subarachnoid hemorrhage. These clinicaltools allow us to reduce variations in care and thus facilitateexcellence and efficiency in patient management of this diverse andoften medically challenging patient population. The UCLA Stroke Centerand Neurovascular Program coordinate the following programs thatsupport clinical research and optimal patient care:
Study Purpose Design Diffusion/Perfusion To demonstrate the efficacy of intra-venous and Single center, open nonrandomized MR in Thrombolysis intra-arterial clot-dissolving medication using trial. Large vessel occlusion. Initiation Diffusion/Perfusion MR. within 6 hours of symptom onset. Vitamin in Stroke To determine whether multivitamins with high Multicenter, double-blind, randomized Prevention (VISP) or low dose folic acid supplement reduces trial. Age 35-85. Enrollment within 120 the risk of new vascular events in stroke patients. days of nondisabling cerebral infarction. Unruptured Aneurysm Trial To determine the optimal treatment for unruptured Multicenter, observational, cohort study. aneurysms (surgery vs medical management). WASID To determine whether aspirin or warfarin is more Multicenter, double-blind, randomized effective in preventing recurrent stroke in patients trial. Treatment assignment within with intracranial stenoses. 90 days of prior stroke or TIA. Clomethiazole (CLASS) To demonstrate the efficacy of the Clomethiazole in patients with acute neuroprotective agent. ischemic stroke. Randomized, double- blind trial. Treatment within 12 hours of symptom onset. MR Imaging in Stroke To use diffusion/perfusion magnetic resonance Randomized, double-blind trial. Treatment imaging to demonstrate the efficacy of the Treatment within 12 hours of symptom neuroprotective agent magnesium in patients onset. with acute ischemic stroke. BRAVO To demonstrate the efficacy of the novel Randomized, double-blind trial. antiplatelet agent Lotrafiban added to aspirin Treatment within 30 days of a stroke or for prevention of stroke and other vascular transient ischemic attack. events. Magnesium in the Field To test the safety and explore the effectiveness Open-label treatment trial. Treatment of paramedics administering the neuroprotective within 12 hours of symptom onset. agent magnesium to acute stroke patients in the field. UCLA Stroke Center
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