***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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    ***EXAMPLES*** 
    Input: Two hundred forty-nine well-characterized difficult distal bypasses , entered into a multicenter dextran 40 trial , were reevaluated after 3 years . Seventy in situ ( IS ) vein grafts , 49 reversed saphenous ( RS ) vein grafts , 60 polytetrafluoroethylene ( PTFE ) grafts , and 70 umbilical vein ( UV ) grafts were used . Primary and secondary patency rates at 3 years were , respectively , 84 % and 90 % for IS , 66 % and 73 % for RS , 35 % and 48 % for PTFE , and 24 % and 32 % for UV . Subgroup analysis according to the site of distal anastomosis showed no significant differences in primary patency among these grafts at the above-knee level but significant differences between both vein grafts ( IS and RV ) and the others ( PTFE and UV ) below the knee ( 78 % vs 31 % , respectively ) . This difference increased at the tibial level ( 78 % vs 10 % ) but there was also a significant difference between IS grafts ( 88 % ) and RS grafts ( 63 % ) at this level . Hazard functional analysis showed all grafts except IS grafts begin to fail at an increasing rate again by 24 months . Although overall results appeared to favor PTFE over UV , 62 % of PTFE vs 16 % of UV terminated at the above-knee level and the patency results of these two grafts were not significantly different at any level . The only other factor than graft type and distal anastomotic site that consistently correlated with late patency was tobacco use . Diabetic patients actually fared significantly better than nondiabetic patients , presumably because of the higher use of IS grafts and lower use of tobacco . The choice of graft overshadows all other factors affecting patency and its influence is magnified with more distal terminal anastomosis Background — Patients with peripheral arterial disease are at high risk of ischemic events and therefore are treated with antithrombotics . In patients with coronary artery disease or cerebrovascular disease , bleeding is related to the subsequent occurrence of ischemic events . Our objective was to assess whether this is also the case in patients with peripheral arterial disease . Methods and Results — All patients from the Dutch Bypass and Oral Anticoagulants or Aspirin ( BOA ) Study , a multicenter r and omized trial comparing oral anticoagulants with aspirin after infrainguinal bypass surgery , were included . The primary outcome event was the composite of nonfatal myocardial infa rct ion , nonfatal ischemic stroke , major amputation , and cardiovascular death . To identify major bleeding as an independent predictor for ischemic events , crude and adjusted hazard ratios with 95 % confidence intervals were calculated with multivariable Cox regression models . From 1995 until 1998 , 2650 patients were included with 101 nonfatal major bleedings .  During a mean follow-up of 14 months , the primary outcome event occurred in 218 patients ; 22 events were preceded by a major bleeding . The mean time between major bleeding and the primary outcome event was 4 months . Major bleeding was associated with a 3-fold increased risk of subsequent ischemic events ( crude hazard ratio , 3.0 ; 95 % confidence interval , 1.9 to 4.6 ; adjusted hazard ratio , 3.0 ; 95 % confidence interval , 1.9 to 4.7 ) . Conclusions — In patients with peripheral arterial disease , as in patients with coronary artery disease or cerebrovascular disease , major bleeding was independently associated with major ischemic complications . Without compromising the benefits of antithrombotics , these findings call for caution relative to the risks of major bleeding Recent clinical studies indicate that the use of aspirin and dipyridamole improves graft patency rates in patients with infrainguinal polytetrafluoroethylene ( PTFE ) grafts and aortocoronary vein grafts . We undertook a prospect i ve , double-blind , r and omized study to determine whether these drugs administered postoperatively to patients with PTFE or autologous vein infrainguinal bypasses would improve graft patency during the first 24 months after operation . Patients received either aspirin 325 mg and dipyridamole 75 mg or identical placebo tablets three times a day , taken orally . Patency rates were compared by computing st and ard life tables and comparing cumulative patency rates .  One hundred patients with 102 grafts were studied . The cumulative patency rate at 24 months was not significantly different for the treatment ( 57 % ) versus control ( 67 % ) groups or for any subgroup . We conclude that aspirin and dipyridamole administered postoperatively in the doses used in this study do not improve the overall patency rates of vein or PTFE infrainguinal bypass grafts OBJECTIVE To compare the consequences of occlusion of infrainguinal venous and prosthetic grafts . METHODS In total , 2690 patients were included in the Dutch BOA study , a multicenter r and omised trial that compared the effectiveness of oral anticoagulants with aspirin in the prevention of infrainguinal bypass graft occlusion . Two thous and four hundred and four patients received a femoropopliteal or femorodistal bypass with a venous ( 64 % ) or prosthetic ( 36 % ) graft . The incidence of occlusion and amputation was calculated according to graft material and the incidence of amputation after occlusion was compared with Cox regression to adjust for differences in prognostic factors . RESULTS The indication for operation was claudication in 51 % , rest pain in 20 % and tissue loss in 28 % of patients . The mean follow up was 21 months . After venous bypass grafting 171 ( 15 % ) femoropopliteal and 96 ( 24 % ) femorodistal grafts occluded . After prosthetic bypass grafting 234 ( 30 % ) femoropopliteal and 25 ( 38 % ) femorodistal grafts occluded . Patients with occlusions in the venous group had more severe ischemia , less runoff vessels and were older than the patients with prosthetic grafts . In the venous occlusion group 54 ( 20 % ) amputations were performed compared to 42 ( 16 % ) in the prosthetic occlusion group ; crude hazard ratio 1.17 ( 95 % CI 0.78 - 1.75 ) . After adjustment for above mentioned differences in patient characteristics the hazard ratio was 0.86 ( 95 % CI 0.56 - 1.32 ) . CONCLUSION The need for amputation after occlusion is not influenced by graft material in infrainguinal bypass surgery OBJECTIVE We aim ed to study the long-term development of health-related quality of life ( HR-QoL ) in patients with peripheral arterial disease after they underwent peripheral bypass surgery  and to evaluate the influence of adverse vascular events that occurred during follow-up . METHODS We compared current HR-QoL scores with previous measurements in patients who participated in the Dutch Bypass and Oral Anticoagulants or Aspirin ( BOA ) Study between 1995 and 1998 after they underwent infrainguinal bypass surgery . Patients from six centers that contributed most to the Dutch BOA Study ( n = 482 ) were followed up retrospectively from 1995 up to 2009 . RESULTS At a mean follow-up of 11 years since BOA r and omization , 165 of the 482 patients were alive of whom 123 ( 75 % ) completed the EQ-5D and R AND -36 question naires . Fifty-three patients completed the question naires three times : at BOA entry , at BOA close-out , and at BOA long-term follow-up . In these patients the HR-QoL scores decreased over time , especially for the physical health dimension . In comparison with the general population , matched for age and gender , the HR-QoL scores at both BOA entry and long-term follow-up were substantially lower , even if the patient 's graft was patent and no other vascular events had occurred . The occurrence of an adverse vascular event worsened the physical health state further . CONCLUSIONS The physical HR-QoL in patients with peripheral arterial disease ( PAD ) after peripheral bypass surgery was highly impaired , independent of graft patency , and deteriorated further over time . An adverse vascular event worsened the physical health state and underlined the importance of atherosclerotic risk management as well as stimulation of physical activity in patients with peripheral arterial disease to preserve OBJECTIVES The purpose of this study was to determine the optimal intensity of oral anticoagulation in patients who participated in a r and omized trial of oral anticoagulants or aspirin after infrainguinal bypass graft surgery . METHODS The distribution of patient-time spent in international normalized ratio ( INR ) classes of 0.5 INR unit was calculated assuming a linear change between successive measurements . INR-specific incidence rates of ischemic and hemorrhagic events were calculated as the ratio of the number of events at a certain INR category and the total patient-time spent in that class . The relationship between INR class and event rates was quantified by rate ratios calculated in a Poisson regression model . RESULTS In 1326 patients ( mean age , 69 years ) 41,928 INR measurements were recorded in 1698 patient-years . Patients spent 50 % of the total time within the target range of 3.0 to 4.5 INR . Most of the patient-time ( 60 % ) was spent between 2.5 and 3.5 INR . For each increasing class of 0.5 INR , the incidence of ischemic events ( n = 154 , INR data on event available in 49 % ) decreased by a factor of 0.97 ( 95 % CI , 0.87 - 1.08 ) . The incidence of major bleeding ( n = 123 , INR data on event available in 65 % ) increased significantly by a factor of 1.27 ( 95 % CI , 1.19 - 1.34 ) for each increasing 0.5 INR category . The optimal target range was 3.0 to 4.0 INR , with an incidence of 3.8 events ( 0.9 ischemic and 2.9 hemorrhagic ) per 100 patient-years . CONCLUSIONS The target range of 3.0 to 4.0 INR is the optimal range of achieved anticoagulation intensity and is safe for the prevention of ischemic events in patients after infrainguinal bypass graft surgery A r and omized , double-blind clinical trial was design ed to assess the effect of aspirin ( ASA ) alone or in combination with dipyridamole ( DIP ) on the patency rates of exp and ed PTFE grafts placed in the infrainguinal position . Forty-nine patients were r and omized into three groups who received three times daily either two placebos ( 17 patients ) , 325 mg ASA and placebo ( 16 patients ) , or 325 mg ASA and 75 mg DIP ( 16 patients ) . The patients were seen at 3-month intervals for 1 year , and coded medication bottles were dispensed and returned pills counted to assess patient compliance . Treatment failure was defined as the first graft occlusion . The data were analyzed using the Breslow statistic for progressively censored survival type data . The 1-year cumulative patency rate for the entire series was 59 % . The rates for above-knee grafts in the ASA group ( 100 % ) and the ASA/DIP group ( 100 % ) were significantly higher than the rates for the placebo group ( 50 % ) ( P = 0.05 ) . The 1-year cumulative patency rates for patients with below-knee grafts were not statistically different among the groups , although the patients who received ASA alone had a higher rate than did the other two groups ( 65 % versus 21 % for placebo and 19 % for ASA/DIP ) . There were fewer occlusions in the above-knee grafts as compared to below-knee grafts in all groups , but the differences were statistically significant only in the ASA/DIP group . There were no statistical differences between the two active treatment groups OBJECTIVES We examined the procedural and 30-day clinical outcomes among patients receiving aspirin and either ticlopidine or clopidogrel during coronary stenting . BACKGROUND Ticlopidine-plus-aspirin has become st and ard antiplatelet therapy for the prevention of thrombotic complications after coronary stenting . Clopidogrel has a similar mechanism of action as ticlopidine , but both its efficacy and its safety as a pharmacologic adjunct to coronary stenting have not been well described . METHODS This single-center , prospect i ve analysis examined the in-hospital procedural and 30-day clinical outcomes among 875 consecutive patients undergoing coronary stenting who received adjunctive aspirin and either clopidogrel ( n = 514 ; 58.7 % ) or ticlopidine ( n = 361 ; 41.3 % ) therapy . RESULTS Procedural success rates were similar among the clopidogrel- ( 99.6 % ) and ticlopidine-treated patients ( 99.4 % ) . Subacute stent thromb 
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There was no difference between the treatment groups for limb amputation or mortality .
For the remaining treatment comparisons there is not currently enough evidence to draw any robust conclusions about the efficacy or safety of the treatment on graft patency after peripheral bypass .
Antiplatelet therapy with aspirin or with aspirin plus dipyridamole had a beneficial effect on primary patency of peripheral bypass grafts compared to placebo or no treatment .
This effect was not evident when evaluating venous grafts alone , but antiplatelet therapy did have a beneficial effect on patency in those who had prosthetic grafts .
There was no evidence of differences in side effects ( including general , gastrointestinal , bleeding or infection ) , amputation , cardiovascular events or mortality between the treatment groups .
We found no difference in primary graft patency when aspirin or aspirin with dipyridamole was compared to a vitamin K antagonist or when clopidogrel with aspirin was compared to aspirin alone .