***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND In patients with ischemic stroke , endovascular treatment results in a higher rate of recanalization of the affected cerebral artery than systemic intravenous thrombolytic therapy . However , comparison of the clinical efficacy of the two approaches is needed . METHODS We r and omly assigned 362 patients with acute ischemic stroke , within 4.5 hours after onset , to  endovascular therapy ( intraarterial thrombolysis with recombinant tissue plasminogen activator [ t-PA ] , mechanical clot disruption or retrieval , or a combination of these approaches ) or intravenous t-PA . Treatments were to be given as soon as possible after r and omization . The primary outcome was survival free of disability ( defined as a modified Rankin score of 0 or 1 on a scale of 0 to 6 , with 0 indicating no symptoms , 1 no clinical ly significant disability despite symptoms , and 6 death ) at 3 months . RESULTS A total of 181 patients were assigned to receive endovascular therapy , and 181 intravenous t-PA .  The median time from stroke onset to the start of treatment was 3.75 hours for endovascular therapy and 2.75 hours for intravenous t-PA ( P<0.001 ) . At 3 months , 55 patients in the endovascular-therapy group ( 30.4 % ) and 63 in the intravenous t-PA group ( 34.8 % ) were alive without disability ( odds ratio adjusted for age , sex , stroke severity , and atrial fibrillation status at baseline , 0.71 ; 95 % confidence interval , 0.44 to 1.14 ; P=0.16 ) . Fatal or nonfatal symptomatic intracranial hemorrhage within 7 days occurred in 6 % of the patients in each group , and there were no significant differences between groups in the rates of other serious adverse events or the case fatality rate . CONCLUSIONS The results of this trial in patients with acute ischemic stroke indicate that endovascular therapy is not superior to st and ard treatment with intravenous t-PA . ( Funded by the Italian Medicines Agency , Clinical Trials.gov number , NCT00640367 . ) Background and Purpose — The only Food and Drug Administration ( FDA ) -approved treatment for acute ischemic stroke is tissue plasminogen activator ( tPA ) given intravenously within 3 hours of symptom onset . An alternative strategy for opening intracranial vessels during stroke is mechanical embolectomy , especially for patients ineligible for intravenous tPA .  Methods — We investigated the safety and efficacy of a novel embolectomy device ( Merci Retriever ) to open occluded intracranial large vessels within 8 hours of the onset of stroke symptoms in a prospect i ve , nonr and omized , multicenter trial . All patients were ineligible for intravenous tPA .  Primary outcomes were recanalization and safety , and secondary outcomes were neurological outcome at 90 days in recanalized versus nonrecanalized patients . Results — Recanalization was achieved in 46 % ( 69/151 ) of patients on intention to treat analysis , and in 48 % ( 68/141 ) of patients in whom the device was deployed . This rate is significantly higher than that expected using an historical control of 18 % ( P<0.0001 ) . Clinical ly significant procedural complications occurred in 10 of 141 ( 7.1 % ) patients . Symptomatic intracranial hemorrhages was observed in 11 of 141 ( 7.8 % ) patients . Good neurological outcomes ( modified Rankin score ≤2 ) were more frequent at 90 days in patients with successful recanalization compared with patients with unsuccessful recanalization ( 46 % versus 10 % ; relative risk [ RR ] , 4.4 ; 95 % CI , 2.1 to 9.3 ; P<0.0001 ) , and mortality was less ( 32 % versus 54 % ; RR , 0.59 ; 95 % CI , 0.39 to 0.89 ; P=0.01 ) . Conclusions — A novel endovascular embolectomy device can significantly restore vascular patency during acute ischemic stroke within 8 hours of stroke symptom onset and provides an alternative intervention for patients who are otherwise ineligible for thrombolytics Background and Purpose — Endovascular mechanical thrombectomy may be used during acute ischemic stroke due to large vessel intracranial occlusion . First-generation MERCI devices achieved recanalization rates of 48 % and , when coupled with intraarterial thrombolytic drugs , recanalization rates of 60 % have been reported . Enhancements in embolectomy device design may improve recanalization rates . Methods — Multi MERCI was an international , multicenter , prospect i ve , single-arm trial of  thrombectomy in patients with large vessel stroke treated within 8 hours of symptom onset . Patients with persistent large vessel occlusion after IV tissue plasminogen activator treatment were included . Once the newer generation ( L5 Retriever ) device became available , investigators were instructed to use the L5 Retriever to open vessels and could subsequently use older generation devices and /or intraarterial tissue plasminogen activator . Primary outcome was recanalization of the target vessel . Results — One hundred sixty-four patients received thrombectomy  and 131 were initially treated with the L5 Retriever .  Mean age±SD was 68±16 years , and baseline median ( interquartile range ) National Institutes of Health Stroke Scale score was 19 ( 15 to 23 ) . Treatment with the L5 Retriever result ed in successful recanalization in 75 of 131 ( 57.3 % ) treatable vessels and in 91 of 131 ( 69.5 % ) after adjunctive therapy ( intraarterial tissue plasminogen activator , mechanical ) . Overall , favorable clinical outcomes ( modified Rankin Scale 0 to 2 ) occurred in 36 % and mortality was 34 % ; both outcomes were significantly related to vascular recanalization . Symptomatic intracerebral hemorrhage occurred in 16 patients ( 9.8 % ) ; 4 ( 2.4 % ) of these were parenchymal hematoma type II . Clinical ly significant procedural complications occurred in 9 ( 5.5 % ) patients . Conclusions — Higher rates of recanalization were associated with a newer generation thrombectomy device compared with first-generation devices , but these differences did not achieve statistical significance . Mortality trended lower and the proportion of good clinical outcomes trended higher , consistent with better recanalization Background Supporting 21st century health care and the practice of evidence -based medicine ( EBM ) requires ubiquitous access to clinical information and to knowledge-based re sources to answer clinical questions . Many questions go unanswered , however , due to lack of skills in formulating questions , crafting effective search strategies , and accessing data bases to identify best levels of evidence . Methods This r and omized trial was design ed as a pilot study to measure the relevancy of search results using three different interfaces for the PubMed search system . Two of the search interfaces utilized a specific framework called PICO , which was design ed to focus clinical questions and to prompt for publication type or type of question asked . The third interface was the st and ard PubMed interface readily available on the Web . Study subjects were recruited from interns and residents on an inpatient general medicine rotation at an academic medical center in the US . Thirty-one subjects were r and omized to one of the three interfaces , given 3 clinical questions , and asked to search PubMed for a set of relevant articles that would provide an answer for each question . The success of the search results was determined by a precision score , which compared the number of relevant or gold st and ard articles retrieved in a result set to the total number of articles retrieved in that set . Results Participants using the PICO templates ( Protocol A or Protocol B ) had higher precision scores for each question than the participants who used Protocol C , the st and ard PubMed Web interface . ( Question 1 : A = 35 % , B = 28 % , C = 20 % ; Question 2 : A = 5 % , B = 6 % , C = 4 % ; Question 3 : A = 1 % , B = 0 % , C = 0 % ) 95 % confidence intervals were calculated for the precision for each question using a lower boundary of zero . However , the 95 % confidence limits were overlapping , suggesting no statistical difference between the groups . Conclusion Due to the small number of search es for each arm , this pilot study could not demonstrate a statistically significant difference between the search protocol s. However there was a trend towards higher precision that needs to be investigated in a larger study to determine if PICO can improve the relevancy of search results Background and Purpose — Little is known in regard to cerebral arterial reocclusion after successful thrombolysis . In the absence of arteriographic information , the National Institute of Neurological Disorders and Stroke ( NINDS ) rt-PA Stroke Trial investigators prospect ively identified clinical deterioration following improvement ( DFI ) as a possible surrogate marker of cerebral arterial reocclusion after rt-PA – induced recanalization . Also , we identified any significant clinical deterioration ( CD ) even if not preceded by improvement . This observational analysis was design ed to determine the incidence of DFI and CD in each treatment group , to identify baseline or posttreatment variables predictive of DFI or CD , and to determine any relationship between DFI , CD , and clinical outcome . Methods — DFI was defined as any 2-point deterioration on the NIH Stroke Scale after an initial 2-point improvement after treatment . CD was defined as any 4-point worsening after treatment compared with baseline . All data were collected prospect ively by investigators blinded to treatment allocation . A noncontrast brain CT was m and ated when a 2-point deterioration occurred . All cases were vali date d by a central review committee . Results — DFI was identified in 81 of the 624 patients ( 13 % ) ; 44 were treated with rt-PA and 37 were treated with placebo ( P = 0.48 ) . DFI occurred more often in patients with a higher baseline NIH Stroke Scale score . CD within the first 24 hours occurred in 98 patients ( 16 % of all patients ) ; 43 were given rt-PA and 55 were given placebo  ( P = 0.19 ) . Baseline variables associated with CD included a less frequent use of prestroke aspirin  and a higher incidence of early CT changes of edema or mass effect or dense middle cerebral artery sign .  Patients with CD had higher rates of increased serum glucose and fibrin degradation products , and they also had higher rates of symptomatic intracranial hemorrhage and death . Patients who experienced either DFI or CD were less likely to have a 3-month favorable outcome . Conclusions — We found no association between DFI , CD , and rt-PA treatment , and no clinical evidence to suggest reocclusion . Deterioration was strongly associated with stroke severity and poor outcome and was less frequent in patients whose stroke occurred while they were on aspirin CONTEXT Intravenous tissue-type plasminogen activator can be beneficial to some patients when given within 3 hours of stroke onset , but many patients present later after stroke onset and alternative treatments are needed . OBJECTIVE To determine the clinical efficacy and safety of intra-arterial ( IA ) recombinant prourokinase ( r-proUK ) in patients with acute stroke of less than 6 hours ' duration caused by middle cerebral artery ( MCA ) occlusion . DESIGN PROACT II ( Prolyse in Acute Cerebral Thromboembolism II ) , a r and omized , controlled , multicenter , open-label clinical trial with blinded follow-up conducted between February 1996 and August 1998 . SETTING Fifty-four centers in the United States and Canada . PATIENTS A total of 180 patients with acute ischemic stroke of less than 6 hours ' duration caused by angiographically proven occlusion of the MCA and without hemorrhage or major early infa rct ion signs on computed tomographic scan . INTERVENTION Patients were r and omized to receive 9 mg of IA r-proUK plus heparin ( n = 121 ) or heparin only ( n = 59 ) . MAIN OUTCOME MEASURES The primary outcome , analyzed by intention-to-treat , was based on the proportion of patients with slight or no neurological disability at 90 days as defined by a modified Rankin score of 2 or less . Secondary outcomes included MCA recanalization , the frequency of intracranial hemorrhage with neurological deterioration , and mortality . RESULTS For the primary analysis , 40 % of r-proUK patients and 25 % of control patients had a modified Rankin score of 2 or less ( P = .04 ) . Mortality was 25 % for the r-proUK group and 27 % for the control group . The recanalization rate was 66 % for the r-proUK group and 18 % for the control group ( P<.001 ) . Intracranial hemorrhage with neurological deterioration within 24 hours occurred in 10 % of r-proUK patients and 2 % of control patients ( P = .06 ) . CONCLUSION Despite an increased frequency of early symptomatic intracranial hemorrhage , treatment with IA r-proUK within 6 hours of the onset of acute ischemic stroke caused by MCA occlusion significantly improved clinical outcome at 90 days BACKGROUND Present mechanical devices are unable to achieve recanalisation in up to 20 - 40 % of large vessel occlusion strokes . We compared efficacy and safety of the Trevo Retriever , a new stent-like device , with its US Food and D 
    Output:
    
Conclusion Stent retrievers have the potential to achieve a high rate of recanalization and functional independence whilst being relatively safe .