***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 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 and Purpose — Experimental evidence indicates that ultrasound can accelerate thrombolysis . We report our findings on early recanalization during transcranial color-coded Doppler ( TCCD ) continuous monitoring in acute stroke patients with middle cerebral artery ( MCA ) main stem occlusion . Methods — We performed continuous TCCD monitorings in 6 consecutive patients with acute MCA main stem occlusion  using a 2-MHz transducer . Patients were not treated with recombinant tissue plasminogen activator . Results — Partial recanalization , defined as blunted waveforms , occurred during monitoring in 5 patients ( 83 % ) . The mean time to beginning of recanalization was 17.2±9.6 minutes . Complete recanalization at 24 hours occurred in only 1 patient . The mean National Institutes of Health Stroke Scale score in the patients who recanalized during monitoring was 21.2±4.1 at baseline , 19.2±5 at 2 hours , and 15.6±3.4 at 24 hours ( P = 0.1 ) . Conclusions — In this short series of patients with acute MCA main stem occlusion , not treated with recombinant tissue plasminogen activator , we found a high rate of early partial recanalization during continuous exposure to 2-MHz ultrasound OBJECT Mechanical thrombectomy is increasingly being used for the treatment of large-vessel ischemic stroke in patients who arrive outside of the 3-hour tissue plasminogen activator time window . In this study , the authors evaluated the cost and effectiveness of mechanical thrombectomy compared with st and ard medical therapy in patients who are ineligible to receive tissue plasminogen activator . METHODS Clinical outcomes of an open-label study of mechanical thrombectomy were compared with a hypothetical control group with a lower recanalization rate ( 18 vs 60 % ) and a lower rate of symptomatic intracranial hemorrhage ( 0.6 vs 7.8 % ) than the active treatment group . A Markov cost-effectiveness model was built to compare the health benefits and costs associated with mechanical thrombectomy compared with st and ard medical therapy . All probabilities , quality -of-life factors , and costs were estimated from the published literature . Univariate sensitivity analyses were performed to assess how variations in model parameters affect health and economic outcomes . RESULTS Treatment of acute ischemic stroke with mechanical thrombectomy increased survival time by 0.54 quality -adjusted life years ( QALYs ) , compared with st and ard medical therapy ( 2.37 vs 1.83 QALYs ) , at an increased cost of $ 6600 . This yielded an incremental cost-effectiveness ratio ( ICER ) of $ 12,120 per QALY gained , a value generally considered cost-effective . Sensitivity analysis showed that mechanical thrombectomy remained cost-effective ( ICER < $ 50,000 per QALY gained ) for all model inputs varied over a reasonable range , except for age at stroke treatment . For patients older than 82 years of age , the treatment was only borderline cost-effective ( ICER of $ 50,000 - 100,000 per QALY gained ) . CONCLUSIONS The treatment of large-vessel ischemic stroke with mechanical thrombectomy appears to be costeffective . These results require validation when data from a r and omized , controlled trial of mechanical thrombectomy become available 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 Intravenous thrombolysis with alteplase is the only approved treatment for acute ischemic stroke , but its efficacy and safety when administered more than 3 hours after the onset of symptoms have not been established . We tested the efficacy and safety of alteplase administered between 3 and 4.5 hours after the onset of a stroke . METHODS After exclusion of patients with a brain hemorrhage or major infa rct ion , as detected on a computed tomographic scan , we r and omly assigned patients with acute ischemic stroke in a 1:1 double-blind fashion to receive treatment with intravenous alteplase ( 0.9 mg per kilogram of body weight ) or placebo . The primary end point was disability at 90 days , dichotomized as a favorable outcome ( a score of 0 or 1 on the modified Rankin scale , which has a range of 0 to 6 , with 0 indicating no symptoms at all and 6 indicating death ) or an unfavorable outcome ( a score of 2 to 6 on the modified Rankin scale ) . The secondary end point was a global outcome analysis of four neurologic and disability scores combined . Safety end points included death , symptomatic intracranial hemorrhage , and other serious adverse events . RESULTS We enrolled a total of 821 patients in the study and r and omly assigned 418 to the alteplase group and 403 to the placebo group . The median time for the administration of alteplase was 3 hours 59 minutes . More patients had a favorable outcome with alteplase than with placebo ( 52.4 % vs. 45.2 % ; odds ratio , 1.34 ; 95 % confidence interval [ CI ] , 1.02 to 1.76 ; P=0.04 ) . In the global analysis , the outcome was also improved with alteplase as compared with placebo ( odds ratio , 1.28 ; 95 % CI , 1.00 to 1.65 ; P<0.05 ) . The incidence of intracranial hemorrhage was higher with alteplase than with placebo ( for any intracranial hemorrhage , 27.0 % vs. 17.6 % ; P=0.001 ; for symptomatic intracranial hemorrhage , 2.4 % vs. 0.2 % ; P=0.008 ) . Mortality did not differ significantly between the alteplase and placebo groups ( 7.7 % and 8.4 % , respectively ; P=0.68 ) . There was no significant difference in the rate of other serious adverse events . CONCLUSIONS As compared with placebo , intravenous alteplase administered between 3 and 4.5 hours after the onset of symptoms significantly improved clinical outcomes in patients with acute ischemic stroke ; alteplase was more frequently associated with symptomatic intracranial hemorrhage . ( Clinical Trials.gov number , NCT00153036 . BACKGROUND The MERCI ( Mechanical Embolus Removal in Cerebral Ischemia ) trial reported efficacy of the Merci Retriever for opening intracranial vessels in patients ineligible for intravenous ( IV ) tissue plasminogen activator ( tPA ) .  Patients who receive IV tPA but do not recanalize may also benefit from thrombectomy , but the revascularization efficacy and safety of this strategy has not been reported . METHODS Multi MERCI is an ongoing international , multicenter , prospect i ve , single-arm trial of patients with large vessel stroke treated within 8 hours 
    Output:
    
Based on observational data , the combination of IV tPA and mechanical thrombectomy for large-vessel ischemic stroke appears to be cost-effective compared to IV tPA alone .