***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: Poor patency of synthetic grafts for infragenicular revascularization has led to use of distal vein patches or cuffs . The aim of this study was to compare the distally widened DistafloTM PTFE graft , which mimics a vein cuff , with a PTFE graft with distal vein modification . In this prospect i ve , r and omized , multicenter trial we compared use of a precuffed PTFE graft wit that of PTFE grafts with distal vein modification for infragenicular revascularization in patients with critical limb ischemia without saphenous vein . Study end points were primary and secondary patency and limb salvage rates at 2 years . From January 28,1999 to November 1 , 2000 , 104 patients were enrolled in 10 North American centers . Thirteen were excluded for protocol violation . Ninety-one bypasses were performed in 89 patients with a mean age of 73 years ( range 47 - 90 ) . By r and omization , 47 bypasses were done with the precuffed graft and 44 with PTFE graft with vein cuff . Both groups were comparable for comorbidities and operative variables , except for a higher incidence of acute ischemia in the precuffed group ( 19 % vs. 4.5 % , p = 0.03 ) . Bypass was a redo procedure in 53 % and was performed at the infrapopliteal vessels in 79 % . Operative mortality was 2.2 % ( 2/91 ) . Mean follow-up was 14 months ( range 1 - 30 ) . At 1 and 2 years , primary patency was 52 % and 49 % for the precuffed group and 62 % and 44 % for the vein cuffed group , respectively ( p = 0.53 ) . At 1 year and 2 years , the limb salvage rate was 72 % and 65 % for the precuffed group and 75 % and 62 % in the vein cuffed group ( p = 0.88 ) . Although numbers are small and follow-up short , this midterm analysis shows similar results for the Distaflo precuffed grafts and PTFE grafts with vein cuff . A precuffed graft is a reasonable alternative conduit for infragenicular reconstruction in the absence of saphenous vein and provides favorable limb salvage 1 . The activities of  phosphofructokinase ( PFK ) , citrate synthetase ( CS ) , lactate dehydrogenase ( LDH ) , 3-hydroxyacyl-CoA dehydrogenase ( ACDH ) and cytochrome-c oxidase(Cyt-ox ) in the calf muscle tissue were compared in subjects with intermittent claudication ( n = 38 ) and controls ( n = 20 ) . The activities of CS , ACDH and Cyt-ox were increased and the activity of Cytox was positively correlated to the maximal walking distance ( MWD ) in the patients . 2 . Thirty-three patients with intermittent claudication were r and omized to three treatment groups : ( 1 ) operative surgery , ( 2 ) operative surgery supplemented with physical training and ( 3 ) physical training alone . Before and after 6 - 12 months of treatment , symptom-free walking distance ( SFWD ) , MWD , ankle-brachial blood pressure quotient ( ankle index ) , maximal plethysmographic calf blood flow ( MPBF ) and the activities of PFK , CS , LDH , ACDH and Cyt-ox were measured . 3 . SFWD and MWD increased in all three groups . Ankle index and MPBF increased in groups 1 and 2 , but were unchanged in group 3 . The activities of Cyt-ox and CS decreased with operation , but the activity of Cyt-ox was further augmented with training in group 3 . Overall , the change in ankle index explained 80 - 90 % of the variability in walking performance . In a separate analysis , the increased activity of Cyt-ox in group 3 was positively correlated to , and explained 31 % of the variability in , the improvement in SFWD . 4 . These findings indicate that both physical activity and a reduced calf blood flow are necessary conditions for the enzymatic adaptation to take place . A causal relationship between metabolic adaptation in the muscle tissue and walking performance is suggested . ( ABSTRACT TRUNCATED AT 250 WORDS Intermittent claudication is the primary symptom of peripheral arterial disease , affecting between 1 and 3 million Americans . Symptomatic improvement can be achieved by endovascular revascularization , but such procedures are invasive , expensive , and may be associated with procedural adverse events . Medical treatment options , including claudication medications and supervised exercise training , are also known to be effective , albeit also with associated limitations . The CLEVER ( Claudication : Exercise Vs . Endoluminal Revascularization ) study , funded by the Heart , Lung , and Blood Institute of the National Institutes of Health , is a prospect i ve , multicenter , r and omized , controlled clinical trial evaluating the relative efficacy , safety , and health economic impact of four treatment strategies for people with aortoiliac peripheral arterial disease and claudication . The treatment arms are : ( 1 ) optimal medical care ( claudication pharmacotherapy ) ; ( 2 ) primary stent placement ; ( 3 ) supervised exercise rehabilitation ; and ( 4 ) combined stenting with supervised exercise rehabilitation . The CLEVER study is a 5-year r and omized , controlled clinical trial to be conducted at approximately 25 centers in the United States that will monitor 252 patients and their responses to treatment during an 18-month follow-up period . The primary end point is change in maximum walking duration on a grade d treadmill test . Secondary end points include the change at 18 months in maximum walking duration from baseline , comparisons of free-living daily activity levels assessed by pedometer , health-related quality of life , and cost-effectiveness . Other analyses include the effect of these treatment strategies on anthropomorphic and physiologic variables , including body mass index , waist circumference , blood pressure , pulse pressure , and resting pulse as well as biochemical markers of cardiovascular health , including fasting lipids , fibrinogen , C-reactive protein , and hemoglobin A 1c values OBJECTIVE Despite many clinical studies , there is still uncertainty as to whether venous material is superior to prosthetic material s for femoropopliteal reconstruction proximal to the knee joint . A prospect ively r and omized clinical trial was design ed to evaluate the effectiveness of reversed saphenous vein in comparison with that of collagen impregnated woven polyester prosthesis in above-knee arterial reconstruction . METHODS In a 3-year period , 103 above-knee femoropopliteal bypass graft operations were performed and followed in 85 patients ( 52 male , 33 female ) . The indication for operation was severe claudication in 74 cases , rest pain in 7 cases , and ulceration in 4 cases . For the bypass graft , a reversed saphenous vein was used in each of 51 cases , and a collagen impregnated woven polyester prosthesis was used in each of 52 cases . Preoperative risk factors were diabetes ( 24 % ) , a history of myocardial infa rct ion ( 23 % ) , and current status with respect to smoking ( 74 % ) . There was no hospital mortality ; 5 % of patients had minor postoperative complications . RESULTS After 2 years of follow-up , the primary patency was 81 % for saphenous vein and 67 % for collagen impregnated woven polyester prosthesis ( P=0.065 ) ; the secondary patency was 81 % for saphenous vein and 77 % for collagen impregnated woven polyester prosthesis ( P=0.298 ) . During this follow-up period of 2 years , we found no statistically significant difference in primary and secondary patency between saphenous vein and collagen impregnated woven polyester prosthesis . We found no predictive factor for the occlusion of either bypass graft . CONCLUSION The use of collagen impregnated woven polyester prosthesis above the knee is a reasonable alternative in femoropopliteal bypass grafting that is associated with acceptable short-term patency rates OBJECTIVE To evaluate the feasibility and efficacy of simultaneous combined endovascular and open lower extremity arterial reconstruction . DESIGN Case series study with retrospective analysis of prospect ively collected non-r and omised data . METHODS Patients were divided into three groups : group 1 and group 2 included patients who underwent endovascular reconstruction proximal and distal to the site of open reconstruction , respectively , whereas group 3 included patients who underwent open surgery with both proximal and distal endoluminal procedures .  Patency analyses were performed using Kaplan-Meier life tables . Univariate and multivariate analyses were used to assess the influence of various risk factors on primary patency . RESULTS Complete data were obtained from 60 patients who underwent 61 single-step hybrid procedures .  Technical and haemodynamic success rates were 100 % and 95 % , respectively . The perioperative mortality rate was 3 % . The primary and assisted- primary patency rates at 12 months were 71 % and 98 % , respectively . Primary patency rates were lower in group 3 when compared with groups 1 and 2 ( log-rank test , p=0.006 ) . The presence of diabetes and dyslipidaemia were independent predictors of decreased primary patency ( p=0.003 and p=0.014 , respectively ) . CONCLUSIONS Hybrid procedures provide an effective treatment management of selected patients with multilevel lower extremity arterial disease . The extent of the disease , diabetes and dyslipidaemia are associated with worse outcome BACKGROUND An intention-to-treat analysis of  r and omized Bypass versus Angioplasty in Severe Ischaemia of the Leg ( BASIL ) trial data showed that initial r and omization to a bypass surgery (BSX)-first strategy was associated with improvements in subsequent overall survival ( OS ) and amputation-free survival ( AFS ) of about 7 and 6 months , respectively . We describe the nature and timing of first , crossover , and re interventions and examine AFS and OS by first treatment received . We also compare vein with prosthetic BSX and transluminal with subintimal balloon angioplasty ( BAP ) and examine outcomes from BSX after failed BAP . METHODS We r and omly assigned 452 patients with SLI due to infrainguinal disease in 27 United Kingdom hospitals to a BSX first ( n = 228 ) or a BAP first ( n = 224 ) revascularization strategy . All patients have been monitored for 3 years and more than half for > 5 years . We prospect ively collected data on every procedure , major amputation , and death . RESULTS Patients r and omized to BAP were more likely to have their assigned treatment first ( 94 % vs 85 % , P = .01 , chi(2)test ) . BAP had a higher immediate technical failure rate of 20 % vs 2.6 % ( P = .01 , chi(2)test ) . By 12 weeks after r and omization 9 BAP ( 4 % ) vs 23 BSX ( 10 % ) patients had not undergone revascularization ; 3 BAP ( 1.3 % ) vs 13 BSX ( 5.8 % ) had undergone the opposite treatment first ; and 35 BAP ( 15.6 % ) and 2 ( 0.9 % ) BSX had received the assigned treatment and then undergone the opposite treatment . BSX distal anastomoses were divided approximately equally between the above and below knee popliteal and crural arteries ; most originated from the common femoral artery . About 25 % of the grafts were prosthetic and > 90 % of vein BSX used ipsilateral great saphenous vein . Most ( 80 % ) BAP patients underwent treatment of the SFA alone ( 38 % ) or combined with the popliteal artery ( 42 % ) and crural arteries ( 20 % ) . Outcome of vein BSX was better for AFS ( P = 0.003 ) but not OS ( P = 0.38 , log-rank tests ) than prosthetic BSX . There were no differences in outcome between approximately equal numbers of transluminal and subintimal BAP . AFS ( P = 0.006 ) but not OS ( P = 0.06 , log rank test ) survival was significantly worse after BSX after failed BAP than after BSX as a first revascularization attempt . CONCLUSIONS BAP was associated with a significantly higher early failure rate than BSX . Most BAP patients ultimately required surgery . BSX outcomes after failed BAP are significantly worse than for BSX performed as a first revascularization attempt . BSX with vein offers the best long term AFS and OS and , overall , BAP appears superior to prosthetic BSX Background Endovascular treatment options for the superficial femoral artery are evolving rapidly . For long lesions , the venous femoropopliteal bypass considered to be superior above the prosthetic bypass . An endoluminal bypass , however , may provide equal patency rates compared to the prosthetic above knee bypass . The introduction of heparin-bonded endografts may further improve patency rates . The SUrgical versus PERcutaneous Bypass ( SuperB ) study is design ed to assess whether a heparin-bonded endoluminal bypass provides equal patency rates compared to the venous bypass and to prove that it is associated with improved quality of life , related to a decreased complication rate , or not . 
    Output:
    
The quality of the evidence for the most important outcomes of bypass surgery versus PTA was high except for clinical improvement and primary patency .
Our analysis has shown that PTA is associated with decreased peri-interventional complications in participants treated for CLI and shorter hospital stay compared with bypass surgery .
Surgical treatment seems to confer improved patency rates up to one year .
Endovascular treatment may be advisable in patients with significant comorbidity , rendering them high risk surgical c and i date s. No solid conclusions can be drawn regarding comparisons of bypass surgery with other treatments because of the paucity of available evidence .