***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: Background and purpose It is unknown what the optimal anticoagulant level is to prevent thromboembolic stroke in patients with left ventricular assist device ( LVAD ) support . We aim ed to evaluate the relation between coagulation status and the occurrence of thromboembolic stroke in HeartMate-II LVAD assisted patients . Methods Thirty-eight consecutive patients with a HeartMate-II LVAD were included . Coagulation status was classified according to INR and aPTT ratio at : 1 ) the moment of first thromboembolic stroke ; and 2 ) during the two weeks preceding the first thromboembolic stroke to assess long-term coagulation status . In patients without stroke , coagulation status was determined just before heart transplant , VAD explantation or death , whichever came first , and at two weeks preceding these surrogate endpoints . Based on coagulation status , patients were divided in two groups : Group I ( reference group ) was defined as INR below 2 and aPTT ratio below 1.5 ; Group II ( adequate anticoagulation ) as INR above 2 or aPTT ratio above 1.5 . Logistic regression analysis was performed to assess the odds ratio for developing stroke for patients with adequate anticoagulation compared to the reference Group . Results Thromboembolic stroke occurred in six ( 16 % ) patients , none within 2 weeks after LVAD implantation . Considering coagulation status at the time of event , patients in coagulation Group II had no decreased risk for thromboembolic stroke ( OR 0.78 ; 95 % CI 0.12–5.0 ) . Results for coagulation status 2 weeks prior of event could not be calculated as all six strokes occurred in Group II . Conclusion In our experience anticoagulation within predefined targets is not associated with a reduced thromboembolic stroke risk in patients with a HeartMate-II LVAD on antiplatelet therapy . However , no firm statement about the effect of either anticoagulant or antiaggregant therapy can be made based on our study . A larger r and omized study is needed to support the hypothesis that there may be no additional benefit of coumarin or heparin therapy compared with antiplatelet therapy alone OBJECTIVES This study sought to evaluate the use of a continuous-flow rotary left ventricular assist device ( LVAD ) as a bridge to heart transplantation . BACKGROUND LVAD therapy is an established treatment modality for patients with advanced heart failure . Pulsatile LVADs have limitations in design precluding their use for extended support . Continuous-flow rotary LVADs represent an innovative design with potential for small size and greater reliability by simplification of the pumping mechanism . METHODS In a prospect i ve , multicenter study , 281 patients urgently listed ( United Network of Organ Sharing status 1A or 1B ) for heart transplantation underwent implantation of a continuous-flow LVAD .  Survival and transplantation rates were assessed at 18 months . Patients were assessed for adverse events throughout the study and for quality of life , functional status , and organ function for 6 months . RESULTS Of 281 patients , 222 ( 79 % ) underwent transplantation , LVAD removal for cardiac recovery , or had ongoing LVAD support at 18-month follow-up . Actuarial survival on support was 72 % ( 95 % confidence interval : 65 % to 79 % ) at 18 months . At 6 months , there were significant improvements in functional status and 6-min walk test ( from 0 % to 83 % of patients in New York Heart Association functional class I or II and from 13 % to 89 % of patients completing a 6-min walk test ) and in quality of life ( mean values improved 41 % with Minnesota Living With Heart Failure and 75 % with Kansas City Cardiomyopathy question naires ) . Major adverse events included bleeding , stroke , right heart failure , and percutaneous lead infection . Pump thrombosis occurred in 4 patients . CONCLUSIONS A continuous-flow LVAD provides effective hemodynamic support for at least 18 months in patients awaiting transplantation , with improved functional status and quality of life . ( Thoratec HeartMate II Left Ventricular Assist System [ LVAS ] for Bridge to Cardiac Transplantation ; NCT00121472 ) BACKGROUND Patients with advanced heart failure have improved survival rates and quality of life when treated with implanted pulsatile-flow left ventricular assist devices as compared with medical therapy . New continuous-flow devices are smaller and may be more durable than the pulsatile-flow devices . METHODS In this r and omized trial , we enrolled patients with advanced heart failure who were ineligible for transplantation , in a 2:1 ratio , to undergo implantation of a continuous-flow device ( 134 patients ) or the currently approved pulsatile-flow device ( 66 patients ) . The primary composite end point was , at 2 years , survival free from disabling stroke and reoperation to repair or replace the device . Secondary end points included survival , frequency of adverse events , the quality of life , and functional capacity . RESULTS Preoperative characteristics were similar in the two treatment groups , with a median age of 64 years ( range , 26 to 81 ) , a mean left ventricular ejection fraction of 17 % , and nearly 80 % of patients receiving intravenous inotropic agents . The primary composite end point was achieved in more patients with continuous-flow devices than with pulsatile-flow devices ( 62 of 134 [ 46 % ] vs. 7 of 66 [ 11 % ] ; P<0.001 ; hazard ratio , 0.38 ; 95 % confidence interval , 0.27 to 0.54 ; P<0.001 ) , and patients with continuous-flow devices had superior actuarial survival rates at 2 years ( 58 % vs. 24 % , P=0.008 ) . Adverse events and device replacements were less frequent in patients with the continuous-flow device . The quality of life and functional capacity improved significantly in both groups . CONCLUSIONS Treatment with a continuous-flow left ventricular assist device in patients with advanced heart failure significantly improved the probability of survival free from stroke and device failure at 2 years as compared with a pulsatile device . Both devices significantly improved the quality of life and functional capacity . ( Clinical Trials.gov number , NCT00121485 . BACKGROUND The HeartWare Ventricular Assist System ( HeartWare Inc , Framingmam , MA ) is a miniaturized implantable , centrifugal design , continuous-flow blood pump . The pivotal bridge to transplant and continued access protocol s trials have enrolled patients with advanced heart failure in a bridge-to-transplant indication . METHODS The primary outcome , success , was defined as survival on the originally implanted device , transplant , or explant for ventricular recovery at 180 days . Secondary outcomes included an evaluation of survival , functional and quality of life outcomes , and adverse events . RESULTS A total of 332 patients in the pivotal bridge to transplant and continued access protocol s trial have completed their 180-day primary end-point assessment . Survival in patients receiving the HeartWare pump was 91 % at 180 days and 84 % at 360 days . Quality of life scores improved significantly , and adverse event rates remain low . CONCLUSIONS The use of the HeartWare pump as a bridge to transplant continues to demonstrate a high 180-day survival rate despite a low rate of transplant . Adverse event rates are similar or better than those observed in historical bridge-to-transplant trials , despite longer exposure times due to longer survival and lower transplant rates Objectives : Left ventricular assist devices ( LVAD ) , used in the setting bridge-to-transplantation and destination therapy , for patients with deteriorating severe heart failure are continuously developing . The second generation , the axial flow pumps , have been introduced since some years . Design : Eleven consecutive patients , seven male , with severe heart failure due to ischemic cardiomyopathy ( n=5 ) , dilated cardiomyopathy ( n=5 ) and cytotoxic ethiology ( n=1 ) were implanted with the HeartMate-II ™ . They were preoperatively treated with inotropic support ( n=9 ) , ventricular assist device ( n=2 ) and mechanical ventilation ( n=4 ) . Results : Eight patients were bridged to transplant after median 155 days ( range , 65 to 316 days ) . One patient is ongoing for 748 days , intended for destination therapy . Ten of eleven patients were discharged after median 64 days ( range , 40 to 105 days ) . Four patients were reoperated due to bleeding . Two embolic events were recorded . One perioperative death . Conclusion : Eleven HM-II ™ LVAD 's have been implanted in our institution with good early results . Eight patients were successfully bridged to heart transplantation . One patient is intended for destination therapy and is ongoing since November 2006 . In these severely ill patients , this technique offers a good chance surviving until heart transplantation . In selected cases the technique also offers the possibility of a permanent support and longevity OBJECTIVES The aim of this study was to conduct an initial clinical evaluation of the new HeartWare Ventricular Assist System ( HeartWare , Inc. , Framingham , Massachusetts ) in a multicenter , prospect i ve , nonr and omized single-arm clinical trial . BACKGROUND Heart failure is a worldwide epidemic . The effectiveness of heart transplantation and medical therapy is limited , result ing in the emergence of mechanical circulatory support as a primary treatment for end-stage heart disease . Left ventricular assist devices that use rotary pumps are small and durable , which might reduce morbidity and mortality during support . METHODS Fifty heart transplant c and i date s with New York Heart Association functional class IV symptoms were supported at 5 international centers by the HeartWare System for 180 days , until heart transplant , myocardial recovery and device explant , or death . Patients who continue to be supported have been followed for a minimum of 2 years . RESULTS Of the 50 patients , 20 ( 40 % ) received transplants , 4 ( 8 % ) had the pump explanted after myocardial recovery , and 17 ( 34 % ) continue support at 2 years . Nine ( 18 % ) patients died during support from sepsis ( n = 3 ) , multiple organ failure ( n = 3 ) , or hemorrhagic stroke ( n = 3 ) . The actual survival at 6 , 12 , and 24 months was 90 % , 84 % , and 79 % , respectively . In the survivors , measures of quality of life showed a significant improvement over baseline values . Significant improvements were found for recognition memory at 3 months after implant ( p = 0.006 ) . The most frequent adverse events were infection and bleeding . CONCLUSIONS Patients with end-stage heart failure can be safely and effectively supported by the HeartWare Ventricular Assist System with improved quality of life and neurocognitive function BACKGROUND The use of left ventricular assist devices is an accepted therapy for patients with refractory heart failure , but current pulsatile volume-displacement devices have limitations ( including large pump size and limited long-term mechanical durability ) that have reduced widespread adoption of this technology . Continuous-flow pumps are newer types of left ventricular assist devices developed to overcome some of these limitations . METHODS In a prospect i ve , multicenter study without a concurrent control group , 133 patients with end-stage heart failure who were on a waiting list for heart transplantation underwent implantation of a continuous-flow pump . The principal outcomes were the proportions of patients who , at 180 days , had undergone transplantation , had cardiac recovery , or had ongoing mechanical support while remaining eligible for transplantation . We also assessed functional status and quality of life . RESULTS The principal outcomes occurred in 100 patients ( 75 % ) . The median duration of support was 126 days ( range , 1 to 600 ) . The survival rate during support was 75 % at 6 months and 68 % at 12 months . At 3 months , therapy was associated with significant improvement in functional status ( according to the New York Heart Association class and results of a 6-minute walk test ) and in quality of life ( according to the Minnesota Living with Heart Failure and Kansas City Cardiomyopathy question naires ) . Major adverse events included postoperative bleeding , stroke , right heart failure , and percutaneous lead infection . Pump thrombosis occurred in two patients . CONCLUSIONS A continuous-flow left ventricular assist device can provide effective hemodynamic support for a period of at least 6 months in patients awaiting heart transplantation , with improved functional status and quality of life . ( Clinical Trials.gov number , NCT00121472 [ Clinical Trials.gov ] . ) BACKGROUND An ongoing challenge in the management of patients with heart failure who receive left ventricular assist devices ( LVADs )  is achieving optimal anticoagulation . Adverse prothrombotic events include hemolysis or pump thrombus ( H/T ) and neurologic events ( NEs ) , and all limit the success of LVAD therapy . Our aim was to study the incidence and clinical outcomes associated with these events in a large single-center cohort . METHODS We retrospectively review ed our prospect ively collected data base of all patients receiving a HeartMate II ( Thoratec Corp , Pleasanton , CA ) LVAD from 2005 to 2012 .  Demographic , clinical , and outcome data were analyzed using st and ard statistical methods . All adverse events were recorded . RESULTS Of 193 patients receiving LVADs , we identified 39 H/T events in 26 ( 13.4 % ) patients and 22 NEs in 19 ( 9.8 % ) patients . Seventy-four percent of events occurred in the last 3 years of the series , during which time 63 % of implants were placed . Of patients with H/T , 
    Output:
    
Conclusions Ischemic stroke and ICH are common after LVAD placement , but heterogeneous event rates are reported in the literature .