Carotid endarterectomy: Practice guidelines. Report of the Ad Hoc Committee to the Joint Council of the Society for Vascular Surgery and the North American Chapter of the International Society for Cardiovascular Surgery

Abstract

In 1989, under the Omnibus Budget Reconciliation Act, the Agency for Health Care Policy and Research was established to enhance the quality, appropriateness, and effectiveness of health care services and access to services. The implementation arm of this agency is the Office of the Forum for Quality and Effectiveness in Health Care. The Joint Council of the Society for Vascular Surgery and the International Society for Cardiovascular Surgery has identified carotid endarterectomy as a surgical practice, within its purview, that is likely to be targeted for review. Therefore, an ad hoc committee was charged to prepare guidelines for carotid endarterectomy. These will be voluntarily submitted to the Forum for their consideration and published as a reference for those interested in reviewing the issue of appropriateness of carotid endarterectomy in managing the treatment of patients with the spectrum of carotid bifurcation disease. Lesions of the brachiocephalic trunks have not been included in this review. The subcommittee reviewed the literature concerning natural history, options for both medical and surgical management, as well as the treatment outcome of patients with carotid bifurcation disease. This report provides guidelines for the appropriate use of carotid endarterectomy. Stroke continues to be the third leading cause of death in the United States in addition to being responsible for major disability among survivors, despite an apparent decline in the stroke mortality rate from 94.8/100,000 population in 1950 to 72.9/100,000 population reported in 1983.1McDowell FH, Caplan LR, eds. Cerebrovascular survey report 1985. For the National Institute of Neurological and Communicative Disorders and Stroke. National Institutes of Health, Public Health Service, Bethesda, Md.Google Scholar Although the decrease in mortality rate is commendable, conflicting data exist as to whether or not the incidence of new strokes is decreasing, with some reports showing no change. 2Garraway WM Whisnant JP Furlan AJ Phillips II, LH Kurland LT O'Fallon WM Declining incidence of stroke.N Engl J Med. 1979; 300: 449-451Crossref PubMed Scopus (204) Google Scholar, 3Kotila M Declining incidence of mortality of stroke?.Stroke. 1984; 15: 255-259Crossref PubMed Scopus (82) Google Scholar, 4Alfredsson L Von Arbin M DeFaire U Mortality and incidence of stroke in Stockholm.BMJ. 1986; 292: 1299-1303Crossref PubMed Scopus (45) Google Scholar, 5Wolf PA O'Neal A D'Agostino RB et al.Declining mortality not declining incidence of stroke: the Framingham study.Stroke. 1989; 20: 158Google Scholar This may lead to an increasing prevalence of disabled patients, which adds immeasurably to the cost of health care. The current annual incidence of stroke is 195/100,000 population, with a death rate of approximately half of this. The incidence increases with age; 300/100,000 men aged 55 to 64 years and 1440/100,000 men aged 75 to 84 years.1McDowell FH, Caplan LR, eds. Cerebrovascular survey report 1985. For the National Institute of Neurological and Communicative Disorders and Stroke. National Institutes of Health, Public Health Service, Bethesda, Md.Google Scholar Approximately two thirds of those individuals who survive stroke for 1 month are permanently disabled to some degree. One half of stroke victims surviving 30 days from onset will continue to survive for at least 5 years, and one third of these survivors will require prolonged inpatient rehabilitation.6The national survey of stroke, a national institute of neurological and communicative disorders and stroke. American Heart Association Inc, 1981Google Scholar Stroke prevalence rates have identified two million surviving stroke victims in the United States. Nearly one half of the strokes in the United States appeared in the distribution of the carotid artery and may be related to carotid bifurcation disease.7Mohr JP Caplan LR Melski JW et al.The Harvard Cooperative Stroke Registry: a prospective registry.Neurology. 1978; 28: 754-762Crossref PubMed Google Scholar Most of these infarctions are associated with an atherosclerotic plaque occurring within 3 cm of the bifurcation of the common carotid artery. The economic burden of stroke is enormous and rapidly escalating. Extrapolating direct and indirect cost to 1985 dollars reveals a total cost of 15.9 to 20.6 billion dollars annually.6The national survey of stroke, a national institute of neurological and communicative disorders and stroke. American Heart Association Inc, 1981Google Scholar In a recent Massachusetts study with conversion to 1985 dollars, the prediction of current stroke cost for male stroke victims age 35 to 54 years is more than $188,000 per patient. The timely identification of patients with carotid bifurcation disease who are at risk for stroke will provide the opportunity to perform carotid bifurcation endarterectomy as a means of stroke prevention. To the extent that carotid endarterectomy can be performed with minimum morbidity and death in those patients who have a risk of sufficient gravity for stroke will dictate the appropriateness of application of this surgical therapeutic modality. Endarterectomy of the carotid bifurcation has been offered as a means of stroke prevention for the past 35 years. It had been used with increasing frequency beginning with 17,000 operations in 1971 and reaching a zenith of 100,000 operations in 1984.8Ernst CB Rutkow IM Cleveland RJ et al.Vascular surgery in the United States.J Vasc Surg. 1987; 6: 611-621PubMed Scopus (58) Google Scholar At that time, the appropriateness of the trend as well as the value of the operation itself was questioned from the perspective of (1) operative indications,9Barnett HJM Plum F Walton JN Carotid endarterectomy—an expression of concern.Stroke. 1984; 15: 941-943Crossref PubMed Scopus (146) Google Scholar (2) morbidity and deaths in community hospitals, 10Easton JD Sherman DG Stroke and mortality rate in carotid endarterectomy; 228 consecutive operations.Stroke. 1977; 8: 565-568Crossref PubMed Google Scholar, 11Brott T Thalinger K The practice of carotid endarterectomy in a large metropolitan area.Stroke. 1984; 15: 950-955Crossref PubMed Scopus (159) Google Scholar and (3) comparative effectiveness of adding operation for stroke prevention versus medical management and risk factor control alone.12Dyken ML Pokras R The performance of endarterectomy for disease of the extracranial arteries of the neck.Stroke. 1984; 15: 948-950Crossref PubMed Scopus (141) Google Scholar Since that time a number of important natural history studies have been published as well as reports of both immediate and long-term outcome of patients undergoing carotid endarterectomy. Several prospective randomized trials were initiated, and a few have been completed or reached end points. It is now possible to make recommendations concerning the indications for carotid endarterectomy based on trial results and retrospective literature reviews. Indications for operation will depend on the lesion, the symptomatic status of the patient, the operative morbidity and mortality rates as defined by an audit of individual surgeons proposing to do the operation, and the appropriate selection of individual patients. Findings that identify patients at high risk for stroke are multiple. They include the symptomatic state of the patient, the nature of the lesion, and perhaps most importantly a combination of both symptom and lesion. Unfortunately, most reports to date have failed to look at these in combination. Patients are either analyzed according to their symptomatic status such as carotid or vertebrobasilar transient ischemic attack (TIA), prior stroke, or global ischemia. Lesions are identified as a function of percent stenosis, surface irregularity or ulceration, size of ulcer, and most recently the tissue characteristics of the atheromatous plaque (calcific versus soft). However, it is probable that the natural history of a patient with multiple hemispheric TIAs as a result of a 90% stenosis with an irregular surface consisting of soft plaque material will be quite different from the patient with a single hemispheric event in whom a nonstenosing plaque is identified with a small ulcer. Yet, no large series has been undertaken to identify and compare these two extremes. Our analysis and recommendations will be organized by symptomatic presentation, but where possible, lesion analysis and alternative methods of management will be presented. Regardless of whether or not the patient undergoes carotid endarterectomy, risk factor control of the patient's disease is desirable. Cessation of smoking, control of hypertension, identification and management of diabetes, control of hyperlipidemia, regular exercise, optimizing body weight, and management of coronary artery disease should occupy an appropriate priority. Transient episodes of hemispheric or monocular dysfunction may represent manifestations of carotid artery lesions that place the patient at excess risk for stroke. These events produce a temporary loss of sensory function, motor function, or vision in one eye that resolves usually within minutes to hours, but by definition, always within 24 hours. However, newer imaging techniques suggest that so-called TIAs may be associated with cumulative and permanent neurologic damage. 13Toole JF The Willis lecture: transient ischemic attacks, scientific method, and new realities.Stroke. 1991; 22: 99-104Crossref PubMed Scopus (53) Google Scholar, 14Grigg MJ Papadakis K Nicolaides AN et al.The significance of cerebral infarction and atrophy in patients with amaurosis fugax and transient ischemic attacks in relation to internal carotid artery stenosis: a preliminary report.J Vasc Surg. 1988; 7: 215-222PubMed Scopus (38) Google Scholar Patients who present with TIAs are the best studied group with respect to their natural history and risk for subsequent stroke. Several problems exist in analyzing the natural history studies. Patients with TIAs who have been monitored usually have not had their lesions characterized by percent stenosis, luminal configuration, and nature of plaque consistency. Furthermore, a different outcome may occur in patients who have had a single event at the time of first evaluation in contrast to the patients who have had multiple events. Natural history studies are also somewhat at variance with respect to subsequent stroke risk, but a composite analysis would suggest that patients who present with TIAs have a 10% to 30% risk of stroke in the distribution of the TIA within the first year of onset of symptoms and 6% per year thereafter for the next 3 years, resulting in approximately a 35% to 50% stroke risk within the first 5 years after the onset of symptoms. 15Whisnant JP Matsumoto M Elveback LR The effect of anti-coagulant therapy on the prognosis of patients with transient cerebral ischemic attacks in a community. Rochester, Minnesota 1965–1969.Mayo Clin Proc. 1973; 48: 844-848PubMed Google Scholar, 16Hass WK Jonas S. Caution, falling rock zone: an analysis of the medical and surgical management of threatened stroke.Proc Inst Med. 1980; 33: 80PubMed Google Scholar, 17Acheson J Hutchinson EC. Observations on the natural history of transient cerebral ischemia.Lancet. 1964; 2: 871Abstract PubMed Scopus (70) Google Scholar, 18Baker RN Ramseyer JC Schwartz WS. Prognosis in patients with transient cerebral ischemic attacks.Neurology (NY). 1968; 18: 1157Crossref PubMed Google Scholar, 19Friedman GD Wilson WS Mosier JM et al.Transient ischemic attacks in a community.JAMA. 1969; 210: 1428Crossref PubMed Scopus (119) Google Scholar, 20Dennis M Bamford J Sandercock P Warlow C Prognosis of transient ischemic attacks in the Oxfordshire community stroke project.Stroke. 1990; 21: 848-853Crossref PubMed Scopus (286) Google Scholar Patients who present with TIAs should have an expedient evaluation to determine origin so that treatment can begin promptly. Evaluation should include a search for arterial lesions, coagulopathy, and cardiac sources of emboli (arrhythmia, valvular disease, mural thrombus, and the like). The best method to identify carotid bifurcation disease noninvasively is duplex scanning. This test can characterize the percent stenosis, determine the nature of plaque consistency, and detect surface irregularity. However, it is essential that the laboratory performing the test have established quality control to be certain that the results are accurate. Although controversial, it may be worthwhile to obtain brain imaging such as CT scanning or magnetic resonance imaging (MRI) to determine whether there are areas of cerebral infarction, or alternative pathology such as brain rumor, arteriovenous malformation, subdural hematoma, aneurysm, or other causes of cerebral symptoms. If a decision is made to proceed with carotid endarterectomy, contrast angiography is currently a preoperative standard. Contrast angiography should not be used for diagnostic purposes alone since it does carry a morbidity and mortality rate, albeit low. Diagnostic information can be obtained noninvasively without risk. Although some surgeons elect to proceed with carotid endarterectomy based on the findings of a carotid duplex scan and brain imaging, without an angiogram, this can only be justified if the duplex scan is performed in a laboratory whose reliability has been well documented with prior correlation of their results and angiographic findings. In addition, the duplex scan study must be of excellent quality and the results unequivocal. The role of duplex scanning as an alternative to angiography is currently in evolution. 21Gelabert HA Moore WS Carotid endarterectomy without angiography.Surg Clin North Am. 1990; 70: 213-223PubMed Google Scholar, 22Moore WS Ziomek S Quiñones-Baldrich WJ et al.Can clinical evaluation and non-invasive testing substitute for arteriography in the evaluation of carotid artery disease?.Ann Surg. 1988; 208: 91-94Crossref PubMed Scopus (77) Google Scholar, 23Wagner WH Treiman RL Cossman DV et al.The diminishing role of diagnostic arteriography in carotid artery disease: duplex scanning as definitive preoperative study.Ann Vasc Surg. 1991; 5: 105-110Abstract Full Text PDF PubMed Scopus (62) Google Scholar, 24Gertler JP Cambria RP Kistler JP et al.Carotid surtery without angiography: noninvasive selection of patients.Ann Vasc Surg. 1991; 5: 253-256Abstract Full Text PDF PubMed Scopus (35) Google Scholar Recently programs have been developed to obtain images of the vascular system by MRI (so-called MR angiography). This is a very promising technique that is still in development. Its accuracy has not yet been validated. The medical management of carotid bifurcation disease involves methods of preventing platelet aggregation and embolization. The use of antiplatelet drugs, specifically aspirin, has been widely advocated. 25The American-Canadian cooperative Study Group persantine-aspirin trial in cerebral ischemia, part II: end point results.Stroke. 1985; 16: 406Crossref PubMed Google Scholar, 26Bousser MJ Eschwege E Hagenau M et al.AICLA controlled trial of aspirin and dipyridamole in the secondary prevention of athero-thrombotic cerebral ischemia.Stroke. 1983; 14: 5Crossref PubMed Scopus (505) Google Scholar, 27The Canadian Cooperative Study Group: a randomized trial of aspirin and sulfimpyrazone in threatened strokes.N Engl J Med. 1978; 299: 53Crossref PubMed Scopus (886) Google Scholar, 28Sorenson PS Pedersen H Marquardsen J et al.Acetylsalicilic acid in the prevention of stroke in patients with reversible ischemic attacks. A Danish cooperative study.Stroke. 1983; 14: 15Crossref PubMed Scopus (165) Google Scholar, 29Fields WS LeMac NA Frankowski RF et al.Controlled trial of aspirin and cerebral ischemia.Stroke. 1977; 8: 301Crossref PubMed Scopus (480) Google Scholar, 30Fields WS LeMac NA Frankowski RF et al.Controlled trial of aspirin and cerebral ischemia. Part II. Surgical group.Stroke. 1985; 16: 406Crossref PubMed Scopus (257) Google Scholar Current recommendations include one to four adult aspirin tablets daily. Other antiplatelet drugs, such as ticlopidine, have undergone clinical evaluation and may soon be available after release by the Food and Drug Administration (FDA). Ticlopidine has been shown to be slightly more effective than aspirin in clinical trials but also carries an increased risk of complications related to the drug itself. It is expensive and currently not approved by the FDA.31Hass WK Easton JD Adams HP et al.A randomized trial comparing ticlopidine hydrochloride with aspirin for the prevention of stroke in high risk patients.N Engl J Med. 1989; 321: 501Crossref PubMed Scopus (1160) Google Scholar Dipyridamole is a safe drug but has not been proved to be more effective, either plain or in combination, than aspirin alone.25The American-Canadian cooperative Study Group persantine-aspirin trial in cerebral ischemia, part II: end point results.Stroke. 1985; 16: 406Crossref PubMed Google Scholar Some clinicians have recommended warfarin anticoagulation for those patients who continue to be symptomatic with antiplatelet drugs. 15Whisnant JP Matsumoto M Elveback LR The effect of anti-coagulant therapy on the prognosis of patients with transient cerebral ischemic attacks in a community. Rochester, Minnesota 1965–1969.Mayo Clin Proc. 1973; 48: 844-848PubMed Google Scholar, 32Jonas S Anticoagulant therapy in cerebrovascular disease: review and meta-analysis.Stroke. 1988; 19: 1043-1048Crossref PubMed Scopus (58) Google Scholar The limitations of antiplatelet drugs can be recognized when the plaque composition is studied. 33Imparato AM Riles TS Mintzer R Baumann FG The importance of hemorrhage in the relationship between gross morphologic characteristics and cerebral symptoms in 376 carotid artery plaques.Ann Surg. 1983; 197: 195-203Crossref PubMed Scopus (245) Google Scholar, 34Lusby RJ Ferrell LD Ehrenfeld WK et al.Carotid plaque hemorrhage: its role in the production of cerebral ischemia.Arch Surg. 1982; 117: 1479-1488Crossref PubMed Scopus (301) Google Scholar, 35Feeley TM Leen EJ Colgan MP et al.Histologic characteristics of carotid artery plaque.J Vasc Surg. 1991; 13: 719-724Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar Although platelet aggregate emboli represent one form of particulate material that can produce TIA and may be favorably influenced by antiplatelet drugs, the release of debris from degenerative atheromatous plaque including an admixture of necrotic atheromatous material will not be influenced by antiplatelet or anticoagulate therapy. Furthermore, high-grade critical stenoses that are in danger of imminent occlusion will probably not be influenced by either antiplatelet or anticoagulant drugs. A number of prospective randomized trials have compared aspirin and other antiplatelet drugs to each other or with placebo. 25The American-Canadian cooperative Study Group persantine-aspirin trial in cerebral ischemia, part II: end point results.Stroke. 1985; 16: 406Crossref PubMed Google Scholar, 26Bousser MJ Eschwege E Hagenau M et al.AICLA controlled trial of aspirin and dipyridamole in the secondary prevention of athero-thrombotic cerebral ischemia.Stroke. 1983; 14: 5Crossref PubMed Scopus (505) Google Scholar, 27The Canadian Cooperative Study Group: a randomized trial of aspirin and sulfimpyrazone in threatened strokes.N Engl J Med. 1978; 299: 53Crossref PubMed Scopus (886) Google Scholar, 28Sorenson PS Pedersen H Marquardsen J et al.Acetylsalicilic acid in the prevention of stroke in patients with reversible ischemic attacks. A Danish cooperative study.Stroke. 1983; 14: 15Crossref PubMed Scopus (165) Google Scholar, 29Fields WS LeMac NA Frankowski RF et al.Controlled trial of aspirin and cerebral ischemia.Stroke. 1977; 8: 301Crossref PubMed Scopus (480) Google Scholar, 30Fields WS LeMac NA Frankowski RF et al.Controlled trial of aspirin and cerebral ischemia. Part II. Surgical group.Stroke. 1985; 16: 406Crossref PubMed Scopus (257) Google Scholar Although all of these studies have shown a tendency toward reduced stroke risk in patients treated with antiplatelet medication, no single study has shown a statistically significant benefit in favor of aspirin when compared with placebo. It was only with the combination of end points including death, myocardial infarction, TIA, and stroke that aspirin has been shown to have statistically significant benefit. It has always been argued that the tendency toward stroke risk reduction would have achieved statistical significance had there been enough patients in the trial. To increase sample size, the patient populations from all trials have been combined in a technique called metaanalysis. When metaanalysis is carried out, there appears to be a 15% stroke risk reduction in favor of aspirin.36Sze PC Reitman D Pincus MM et al.Antiplatelet agents in the secondary prevention of stroke: meta-analysis of the randomized control trials.Stroke. 1988; 19: 436-442Crossref PubMed Scopus (68) Google Scholar This is at best a modest benefit. It is interesting to note that metaanalysis has shown a 40% risk reduction with respect to the end points of myocardial infarction and myocardial infarction related death. This would appear to explain why the admixture of end points including death and myocardial infarction together with TIA and stroke demonstrated a statistically significant benefit in favor of aspirin. The effect on death and myocardial infarction were apparently the most important benefits of aspirin, and its effect on TIA and stroke were less important. The morbidity and mortality rates for patients undergoing carotid endarterectomy for TIAs have shown considerable variability as reported in the literature. The combined rates will vary from 3% to 18%. 37Easton JD Sherman DG Stroke and mortality rate in carotid endarterectomy: 228 consecutive operations.Stroke. 1977; 8: 565-568Crossref PubMed Scopus (196) Google Scholar, 38Byer JA Easton JD Transient cerebral ischemia: review of surgical results.Prague Cardiovas Dis. 1980; 22: 389-396Abstract Full Text PDF PubMed Scopus (7) Google Scholar, 39Brott TG Labutta RJ Kempczinski RF Changing patterns in the practice of carotid endarterectomy in a large metropolitan area.JAMA. 1986; 225: 2609-2612Crossref Scopus (85) Google Scholar, 40Modi JR Finch WT Sumner DS. Update of carotid endarterectomy in two community hospitals: Springfield revisited.Stroke. 1983; 14: 128Google Scholar, 41Hertzer NR Beven EG O'Hara PJ Krajewski LP A prospective study of vein patch angioplasty during carotid endarterectomy. Three-year results for 801 patients and 917 operations.Ann Surg. 1987; 206: 628-635Crossref PubMed Scopus (189) Google Scholar, 42Rubin JR Pitluk HC King TA et al.Carotid endarterectomy in a metropolitan community: the early results after 8,535 operations.J Vasc Surg. 1988; 7: 256-260PubMed Scopus (43) Google Scholar, 43Nunn DB Carotid endarterectomy in patients with territorial transient ischemic attacks.J Vasc Surg. 1988; 8: 447-452PubMed Scopus (21) Google Scholar, 44Edwards WH Morris JA Jenkins JM et al.Evaluating quality, cost-effective health care.Ann Surg. 1991; 213: 433-439Crossref PubMed Scopus (46) Google Scholar The stroke council of the American Heart Association has recommended that morbidity and mortality rate for carotid endarterectomy with TIA as an indication should not exceed 5% for the results to be beneficial when compared with the natural history of the disease.45Beebe UG Clagett GP DeWeese JA et al.Assessing risk associated with carotid endarterectomy.Stroke. 1989; 20: 314-315Google Scholar It is clear that many centers of excellence report a morbidity and mortality rate of considerably less than that. Patients who successfully undergo carotid endarterectomy for symptoms of transient cerebral ischemia will experience a marked risk reduction of stroke in the distribution of the operated artery. The annual stroke rate in patients subsequent to carotid endarterectomy has been reported to be between 1% and 2%, 41Hertzer NR Beven EG O'Hara PJ Krajewski LP A prospective study of vein patch angioplasty during carotid endarterectomy. 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Results of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) 52North American Symptomatic Carotid Endarterectomy Trial NASCET Investigators clinical alert: benefit of carotid endarterectomy for patients with high-grade stenosis of the internal carotid artery.Stroke. 1991; 22: 816-817Crossref PubMed Scopus (301) Google Scholar, 53Reinmuth OM Dyken Jr, ML Carotid endarterectomy: bright light at the end of the tunnel.Stroke. 1991; 22: 835-836Crossref PubMed Scopus (7) Google Scholar, 54N Engl J Med. 1991; 325: 445-453Crossref PubMed Scopus (7862) Google Scholar and European Carotid Surgery Trial (ESCT) 55European Carotid Surgery Trialist's Collaborative GroupMRC European carotid surgery trial: interim results for symptomatic patients with severe (70–99%) or with mild (0–29%) carotid stenosis.Lancet. 1991; 337: 1235-1243Abstract PubMed Scopus (3126) Google Scholar, 56Editorial: operating to prevent stroke.Lancet. 1991; 337: 1255-1256Abstract PubMed Scopus (10) Google Scholar, 57Robinson RW Dimirel M LeBeau RJ Natural history of cerebral thrombosis: 9–19 year follow-up.J Chron Dis. 1968; 21: 221-230Abstract Full Text PDF PubMed Scopus (36) Google Scholar, 58Enger E Boyesen S. Long term anticoagulant therapy in patients with cerebral infarction: a controlled clinical study.Acta Med Scand. 1965; 178: 1Google Scholar have now definitely established the increased stroke risk of symptomatic patients with stenoses 70% or greater in spite of aspirin therapy. The aspirin dose was 1300 mg/day. It was disappointing that aspirin failed to be more effective in view of the fact that previous studies would have suggested otherwise. 25The American-Canadian cooperative Study Group persantine-aspirin trial in cerebral ischemia, part II: end point results.Stroke. 1985; 16: 406Crossref PubMed Google Scholar, 26Bousser MJ Eschwege E Hagenau M et al.AICLA controlled trial of aspirin and dipyridamole in the secondary prevention of athero-thrombotic cerebral ischemia.Stroke. 1983; 14: 5Crossref PubMed Scopus (505) Google Scholar, 27The Canadian Cooperative Study Group: a randomized trial of aspirin and sulfimpyrazone in threatened strokes.N Engl J Med. 1978; 299: 53Crossref PubMed Scopus (886) Google Scholar, 28Sorenson PS Pedersen H Marquardsen J et al.Acetylsalicilic acid in the prevention of stroke in patients with reversible ischemic attacks. A Danish cooperative study.Stroke. 1983; 14: 15Crossref PubMed Scopus (165) Google Scholar, 29Fields WS LeMac NA Frankowski RF et al.Controlled trial of aspirin and cerebral ischemia.Stroke. 1977; 8: 301Crossref PubMed Scopus (480) Google Scholar In contrast, the risk reduction of stroke and/or death in patients treated with carotid endarterectomy was highly statistically significant. (See section on clinical trials) Carotid endarterectomy is appropriate for the following circumstances as long as the combined operative morbidity and mortality is kept under 5% in this category. Patients who present with multiple TIAs in the distribution of the diseased carotid artery with lesions of high-grade stenosis, low profile plaques with ulceration, or plaques of mixed consistency represent a clear indication for carotid endarterectomy. Patients who experience a single TIA and who have a demonstrable carotid bifurcation lesion in excess of 70% diameter stenosis also represent a clear indication for operation. Finally, patients who experience recurrent TIAs while on antiplatelet drugs and who have an accessible lesion of the carotid bifurcation (stenosis, ulceration, or plaque of mixed consistency) are candidates for carotid endarterectomy as long as no other cause of the symptoms can be identified. Patients who are at high risk for operation and have a limited life expectancy may be considered candidates for medical management in contrast to operative intervention. Patients who experience a single TIA in the presence of a low profile plaque should have an initial trial of medical management. Recurrent symptoms on antiplatelet drugs would then constitute a failure of medical management and an indication for operation. Many patients will experience a stroke and make an excellent recovery with minimal or no residual deficit. These patients should be evaluated with regard to candidacy for carotid endarterectomy. The question arises as to how much deficit should be considere