***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: Since the 1950s carotid endarterectomy has been performed in patients with symptomatic carotid artery stenosis , based on suggestive but inconclusive evidence for its effectiveness . Only during the last 5 years have r and omized studies clarified the indications for surgery . In preparing this report , panel members used the same rules of evidence used in the previous report1 2 ( Table ⇓ ) . View this table : Table 1 . Levels of Evidence and Grading of Recommendations Few studies have analyzed control of risk factors in a r and omized , prospect i ve manner following carotid endarterectomy . However , a wealth of data are available regarding the general relationship between risk factor control and stroke risk . These data provide some guidance for the care of endarterectomy patients . # # # Hypertension Hypertension is the most powerful , prevalent , and treatable risk factor for stroke.3 Both systolic and diastolic blood pressure are independently related to stroke incidence . Isolated systolic hypertension , which is common in the elderly , also considerably increases risk of stroke . Reduction of elevated blood pressure significantly lowers risk of stroke . Meta-analyses of r and omized trials found that an average reduction in diastolic blood pressure of 6 mm Hg produces a 42 % reduction in stroke incidence.3 4 Treatment of isolated systolic hypertension in people older than 60 years also reduces stroke incidence by 36 % without an excessive number of side effects such as depression or dementia.5 Long-term care of patients after endarterectomy should include careful control of hypertension ( Grade A recommendation for treatment of hypertension in general ; Grade C recommendation for postendarterectomy care ) . Perioperative treatment of hypertension  after carotid endarterectomy represents a special situation . Poor control of blood pressure after endarterectomy increases risk of cerebral hyperperfusion syndrome.6 7 8 9 This complication is characterized by unilateral headache , seizures , and occasionally altered mental status or focal neurological signs . Neuroimaging may show intracerebral hemorrhages10 11 12 or white OBJECTIVE To determine whether the addition of carotid endarterectomy to aggressive medical management can reduce the incidence of cerebral infa rct ion in patients with asymptomatic carotid artery stenosis . DESIGN Prospect i ve , r and omized , multicenter trial . SETTING Thirty-nine clinical sites across the United States and Canada . PATIENTS Between December 1987 and December 1993 , a total of 1662 patients with asymptomatic carotid artery stenosis of 60 % or greater reduction in diameter were r and omized ; follow-up data are available on 1659 . At baseline , recognized risk factors for stroke were similar between the two treatment groups . INTERVENTION Daily aspirin administration and medical risk factor management for all patients ; carotid endarterectomy for patients r and omized to receive surgery . MAIN OUTCOME MEASURES Initially , transient ischemic attack or cerebral infa rct ion occurring in the distribution of the study artery and any transient ischemic attack , stroke , or death occurring in the perioperative period . In March 1993 , the primary outcome measures were changed to cerebral infa rct ion occurring in the distribution of the study artery or any stroke or death occurring in the perioperative period . RESULTS After a median follow-up of 2.7 years , with 4657 patient-years of observation , the aggregate risk over 5 years for ipsilateral stroke and any perioperative stroke or death was estimated to be 5.1 % for surgical patients and 11.0 % for patients treated medically ( aggregate risk reduction of 53 % [ 95 % confidence interval , 22 % to 72 % ] ) . CONCLUSION Patients with asymptomatic carotid artery stenosis of 60 % or greater reduction in diameter and whose general health makes them good c and i date s for elective surgery will have a reduced 5-year risk of ipsilateral stroke if carotid endarterectomy performed with less than 3 % perioperative morbidity and mortality is added to aggressive management of modifiable risk factors BACKGROUND The efficacy of carotid endarterectomy in patients with asymptomatic carotid stenosis has not been confirmed in r and omized clinical trials , despite the widespread use of operative intervention in such patients . METHODS We conducted a multicenter clinical trial at 11 Veterans Affairs medical centers to determine the effect of carotid endarterectomy on the combined incidence of transient ischemic attack , transient monocular blindness , and stroke . We studied 444 men with asymptomatic carotid stenosis shown arteriographically to reduce the diameter of the arterial lumen by 50 percent or more . The patients were r and omly assigned to optimal medical treatment including antiplatelet medication ( aspirin ) plus carotid endarterectomy ( the surgical group ; 211 patients ) or optimal medical treatment alone ( the medical group ; 233 patients ) . All the patients at each center were followed independently by a vascular surgeon and a neurologist for a mean of 47.9 months . RESULTS The combined incidence of ipsilateral neurologic events was 8.0 percent in the surgical group and 20.6 percent in the medical group ( P < 0.001 ) , giving a relative risk ( for the surgical group vs. the medical group ) of 0.38 ( 95 percent confidence interval , 0.22 to 0.67 ) . The incidence of ipsilateral stroke alone was 4.7 percent in the surgical group and 9.4 percent in the medical group . An analysis of stroke and death combined within the first 30 postoperative days showed no significant differences . Nor were there significant differences between groups in an analysis of all strokes and deaths ( surgical , 41.2 percent ; medical , 44.2 percent ; relative risk , 0.92 ; 95 percent confidence interval , 0.69 to 1.22 ) . Overall mortality , including postoperative deaths , was primarily due to coronary atherosclerosis . CONCLUSIONS Carotid endarterectomy reduced the overall incidence of ipsilateral neurologic events in a selected group of male patients with asymptomatic carotid stenosis . We did not find a significant influence of carotid endarterectomy on the combined incidence of stroke and death , but because of the size of our sample , a modest effect could not be excluded BACKGROUND Percutaneous transluminal angioplasty and stenting ( endovascular treatment ) can be used to treat carotid stenosis , but risks and benefits are uncertain . We therefore compared endovascular treatment with conventional carotid surgery . METHODS In a multicentre clinical trial , we r and omly assigned 504 patients with carotid stenosis to endovascular treatment ( n=251 ) or carotid endarterectomy ( n=253 ) . For endovascular patients treated successfully , we used stents in 55 ( 26 % ) and balloon angioplasty alone in 158 ( 74 % ) . An independent neurologist followed up patients . Analysis was by intention to treat . FINDINGS The rates of major outcome events within 30 days of first treatment did not differ significantly between endovascular treatment and surgery ( 6.4 % vs 5.9 % , respectively , for disabling stroke or death ; 10.0 % vs 9.9 % for any stroke lasting more than 7 days , or death ) . Cranial neuropathy was reported in 22 ( 8.7 % ) surgery patients , but not after endovascular treatment ( p<0.0001 ) . Major groin or neck haematoma occurred less often after endovascular treatment than after surgery ( three [ 1.2 % ] vs 17 [ 6.7 % ] , p<0.0015 ) . At 1 year after treatment , severe ( 70 - 99 % ) ipsilateral carotid stenosis was more usual after endovascular treatment ( 25 [ 14 % ] vs seven [ 4 % ] , p<0.001 ) . However , no substantial difference in the rate of ipsilateral stroke was noted with survival analysis up to 3 years after r and omisation ( adjusted hazard ratio=1.04 , 95 % CI 0.63 - 1.70 , p=0.9 ) . INTERPRETATION Endovascular treatment had similar major risks and effectiveness at prevention of stroke during 3 years compared with carotid surgery , but with wide CIs . Endovascular treatment had the advantage of avoiding minor complications OBJECTIVE Current clinical trials evaluating carotid stenting have focused on high-risk patients and may not reflect the broad population of patients with carotid stenosis who undergo treatment to prevent stroke . The Carotid Revascularization Using Endarterectomy or Stenting Systems ( CaRESS ) phase I study is a multicenter , prospect i ve , nonr and omized trial design ed to address the question of whether carotid stenting ( CAS ) with cerebral protection is comparable to carotid endarterectomy ( CEA ) in patients with symptomatic and asymptomatic carotid stenosis . METHODS Patients with symptomatic ( with > 50 % stenosis ) or asymptomatic ( with > 75 % stenosis ) carotid stenosis were entered into the study in a 2:1 ratio of carotid stent and GuardWire Plus distal protection device . This unique trial model was developed through collaboration with the International Society of Endovascular Specialists , the Food and Drug Administration , the Centers for Medicare and Medicaid Services , the National Institutes of Health , and industry representatives . The primary end points included death and stroke at 30 days and a composite 1-year end point of death , stroke , or myocardial infa rct ion ( MI ) from 0 to 30 days and death or stroke from 31 days to 1 year . The secondary end points included residual stenosis , restenosis , repeat angiography , and carotid revascularization at 30 days and 1 year and quality -of-life changes at 1 year . RESULTS A total of 397 patients ( 254 CEA and 143 CAS ) were enrolled in the study : 32 % were symptomatic and 68 % were asymptomatic . There were no significant differences in patient characteristics , symptoms , or surgical risk profiles between groups at baseline . Kaplan-Meier analysis revealed no significant differences in combined death/stroke rates at 30 days ( 3.6 % CEA vs 2.1 % CAS ) or at 1 year ( 13.6 % CEA vs 10.0 % CAS ) . Similarly , there was no significant difference in the combined end point of death , stroke , or MI at 30 days ( 4.4 % CEA vs 2.1 % CAS ) or at 1 year ( 14.3 % CEA vs 10.9 % CAS ) . There were no significant differences between CEA and CAS in the secondary end points of residual stenosis ( 0 % CEA vs 0.9 % CAS ) , restenosis ( 3.6 % CEA vs 6.3 % CAS ) , repeat angiography ( 2.1 % CEA vs 3.6 % CAS ) , carotid revascularization ( 1.0 % CEA vs 1.8 % CAS ) , or change in quality of life ( -1.56 points CEA vs -4.22 points CAS ) . CONCLUSIONS The CaRESS phase I study suggests that the 30-day and 1-year risk of death , stroke , or MI with CAS is equivalent to that with CEA in symptomatic and asymptomatic patients with carotid stenosis BACKGROUND Among patients with substantial carotid artery narrowing but no recent neurological symptom ( stroke or transient ischaemia ) , the balance of surgical risks and long-term benefits from carotid endarterectomy ( CEA ) was unclear . METHODS During 1993 - 2003 , 3120 asymptomatic patients with substantial carotid narrowing were r and omised equally between immediate CEA ( half got CEA by 1 month , 88 % by 1 year ) and indefinite deferral of any CEA ( only 4 % per year got CEA ) and were followed for up to 5 years ( mean 3.4 years ) . Kaplan-Meier analyses of 5-year risks are by allocated treatment . FINDINGS The risk of stroke or death within 30 days of CEA was 3.1 % ( 95 % CI 2.3 - 4.1 ) . Comparing all patients allocated immediate CEA versus all allocated deferral , but excluding such perioperative events , the 5-year stroke risks were 3.8 % versus 11 % ( gain 7.2 % [ 95 % CI 5.0 - 9.4 ] , p<0.0001 ) . This gain chiefly involved carotid territory ischaemic strokes ( 2.7 % vs 9.5 % ; gain 6.8 % [ 4.8 - 8.8 ] , p<0.0001 ) , of which half were disabling or fatal ( 1.6 % vs 5.3 % ; gain 3.7 % [ 2.1 - 5.2 ] , p<0.0001 ) , as were half the perioperative strokes . Combining the perioperative events and the non-perioperative strokes , net 5-year risks were 6.4 % versus 11.8 % for all strokes ( net gain 5.4 % [ 3.0 - 7.8 ] , p<0.0001 ) , 3.5 % versus 6.1 % for fatal or disabling strokes ( net gain 2.5 % [ 0.8 - 4.3 ] , p=0.004 ) , and 2.1 % versus 4.2 % just for fatal stro 
    Output:
    
Meta- analysis of trials to date shows CAS is associated with higher 30-day risk of stroke/death compared with CEA .
Thus , for the patient at average surgical risk , the role of CAS is unproven , especially for symptomatic patients .
And for the patient at high surgical risk , the role of any intervention is uncertain in the setting of competing comorbidities .