Antiplatelet drugs in femoropopliteal vein bypasses: a multicenter trial. Efficacy of oral anticoagulants compared with aspirin after infrainguinal bypass surgery (The Dutch Bypass Oral Anticoagulants or Aspirin Study): a randomised trial. Effect of dipyridamole plus aspirin on hemodialysis graft patency. Benefits, morbidity, and mortality associated with long-term administration of oral anticoagulant therapy to patients with peripheral arterial bypass procedures: a prospective randomized study. Low-molecular weight heparin versus aspirin and dipyridamole after femoropopliteal bypass grafting. Anti-platelet therapy in graft thrombosis: results of a prospective, randomized, double-blind study. [A clinical trial of using antiplatelet therapy to prevent restenosis following peripheral artery angioplasty and stenting]. Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients. A randomized comparison of antiplatelet and anticoagulant therapy after the placement of coronary-artery stents. Effect of aspirin and dipyridamole on the patency of lower extremity bypass grafts.
To evaluate the influence of antiplatelet drugs on patency in femoropopliteal vein bypasses, 48 vascular surgeons recruited 549 patients to a randomized double-blind trial of aspirin (300 mg) + dipyridamole (150 mg) or placebo twice daily starting 2 days before surgery and continuing indefinitely. Graft occlusion measured objectively by independent coordinators and cardiovascular events (myocardial infarction or stroke) were studied, expressed by life table, and analyzed statistically by log rank and confidence intervals (95% CI). Randomization achieved comparable groups with 60% of grafts inserted for rest pain or gangrene. Operative complications on aspirin plus dipyridamole included 18 reoperations for bleeding and 12 hematomas compared with 9 and 14, respectively, on placebo (NS). Most of the 172 graft failures occurred early with failure rates of 43/1000 patient-months in the first 3 months, reducing to 17/1000 at 6 to 12 months, and under 10/1000 in subsequent years. Cumulative graft patency on placebo was 72%, 62%, and 60% at 1, 2, and 3 years, respectively, compared with 78%, 70%, and 61% on aspirin plus dipyridamole. The difference in patency of 6.1% (95% CI, -3% to 15.5%) at 1 year and 8.0% (95% CI, -5% to 21%) at 2 years failed to achieve significance (p = 0.43). On mean follow-up of 34 months, 53 (132/1000 patient-years) cardiovascular events (myocardial infarction or cerebrovascular accident) occurred in patients on placebo compared with only 35 (73/1000) on aspirin plus dipyridamole, a significant difference of 59/1000 (p = 0.004). Antiplatelet therapy had little influence on femoropopliteal vein patency, but subsequent myocardial infarction and stroke was reduced in these patients with peripheral vascular disease. Oral anticoagulants and aspirin are antithrombotic drugs that are commonly used in patients with vascular disease. We investigated whether either of these treatments prevented more effectively than the other bypass complications after infrainguinal bypass surgery.
                We did a multicentre, randomised, open trial. 2690 patients who had undergone infrainguinal grafting were randomly assigned oral anticoagulants (target international normalised ratio 3.0-4.5, n=1339) or aspirin (80 mg daily, n=1351). We followed up patients for a mean of 21 months. The primary outcome was graft occlusion.
                308 graft occlusions occurred in the oral-anticoagulants group compared with 322 in the aspirin group (hazard ratio 0.95 [95% CI 0.82-1.11]), which suggested no overall advantage for either treatment. Oral anticoagulants were beneficial in patients with vein grafts (0.69 [0.54-0.88]), whereas aspirin had better results for nonvenous grafts (1.26 [1.03-1.55]). The composite outcome of vascular death, myocardial infarction, stroke, or amputation occurred 248 times in the oral-anticoagulants group and 275 times in the aspirin group (0.89 [0.75-1.06]). Patients treated with oral anticoagulants had more major bleeding episodes than those treated with aspirin (108 vs 56; 1.96 [1.42-2.71]).
                Oral anticoagulation was better for the prevention of infrainguinal-vein-graft occlusion and for lowering the rate of ischaemic events. Aspirin was better for the prevention of non-venous graft occlusion, and was associated with fewer bleeding episodes. Arteriovenous graft stenosis leading to thrombosis is a major cause of complications in patients undergoing hemodialysis. Procedural interventions may restore patency but are costly. Although there is no proven pharmacologic therapy, dipyridamole may be promising because of its known vascular antiproliferative activity.
                We conducted a randomized, double-blind, placebo-controlled trial of extended-release dipyridamole, at a dose of 200 mg, and aspirin, at a dose of 25 mg, given twice daily after the placement of a new arteriovenous graft until the primary outcome, loss of primary unassisted patency (i.e., patency without thrombosis or requirement for intervention), was reached. Secondary outcomes were cumulative graft failure and death. Primary and secondary outcomes were analyzed with the use of a Cox proportional-hazards regression with adjustment for prespecified covariates.
                At 13 centers in the United States, 649 patients were randomly assigned to receive dipyridamole plus aspirin (321 patients) or placebo (328 patients) over a period of 4.5 years, with 6 additional months of follow-up. The incidence of primary unassisted patency at 1 year was 23% (95% confidence interval [CI], 18 to 28) in the placebo group and 28% (95% CI, 23 to 34) in the dipyridamole-aspirin group, an absolute difference of 5 percentage points. Treatment with dipyridamole plus aspirin significantly prolonged the duration of primary unassisted patency (hazard ratio, 0.82; 95% CI, 0.68 to 0.98; P=0.03) and inhibited stenosis. The incidences of cumulative graft failure, death, the composite of graft failure or death, and serious adverse events (including bleeding) did not differ significantly between study groups.
                Treatment with dipyridamole plus aspirin had a significant but modest effect in reducing the risk of stenosis and improving the duration of primary unassisted patency of newly created grafts. (ClinicalTrials.gov number, NCT00067119.)
                2009 Massachusetts Medical Society The benefits of the long-term administration of oral anticoagulant therapy remain unclear in patients with lower extremity arterial bypass surgery. We studied the effect of warfarin plus aspirin therapy (WASA) versus aspirin therapy alone (ASA) on patient mortality, morbidity and bypass patency rates in a randomized clinical trial.
                In a multicenter, prospective, nonmasked clinical trial, 831 patients who underwent peripheral arterial bypass surgery were compared in a long-term treatment program of WASA (target international normalized ratio of 1.4 to 2.8; 325 mg/day) with ASA (325 mg/day). The primary end point was bypass patency, and mortality and morbidity were the secondary endpoints.
                There were 133 deaths in the WASA group (31.8%) and 95 deaths in the ASA group (23.0%; risk ratio, 1.41; 95% confidence interval, 1.09 to 1.84; P =.0001). Major hemorrhagic events occurred more frequently in the WASA group (WASA, n = 35; ASA, n = 15; P =.02). In the prosthetic bypass group, there was no significant difference in patency rate in the 8-mm bypass subgroup, but there was a significant difference in patency rate in the 6-mm bypass subgroup (femoral-popliteal; 71.4% in the WASA group versus 57.9% in the ASA group; P =.02). In the vein bypass group, patency rate was unaffected (75.3% in the WASA group versus 74.9% in the ASA group).
                The long-term administration of warfarin therapy when combined with aspirin therapy has only a few selected indications for improvement of bypass patency and is associated with an increased risk of morbidity and mortality. Low-molecular weight heparin has theoretical advantages over aspirin and dipyridamole in maintaining vascular-graft patency by virtue of its better antithrombotic effect and antiproliferative activity on vascular, smooth-muscle cells. We tested the hypothesis that low-molecular weight heparin would be more effective than aspirin and dipyridamole in maintaining graft patency in patients undergoing femoropopliteal bypass grafting. Patients were randomised to receive either a daily injection of 2500 IU low-molecular weight heparin, or 300 mg aspirin with 100 mg dipyridamole 8 hourly for 3 months. 94 patients were randomised to low-molecular weight heparin and 106 to aspirin and dipyridamole. Patients were stratified according to indication for surgery and were followed up for 1 year. Kaplan-Meier estimate of graft patency showed 87% graft survival on low-molecular-weight heparin and 72% on aspirin and dipyridamole at 6 months. At 12 months, the respective figures were 78% and 64%. Stratified survival analysis showed that this benefit was confined to those having salvage surgery (log rank test p = 0.0006); for those having surgery for claudication there was no significant benefit. No major bleeding events occurred in either group. We conclude that low-molecular weight heparin is better than aspirin and dipyridamole in maintaining femoropopliteal-graft patency in patients with critical limb ischaemia undergoing salvage surgery. This treatment should have considerable cost benefits. Hemodialysis (HD) vascular access thrombosis remains a major cause of morbidity, accounting for 17.4% of all HD patient hospital admissions in 1986. We initiated this prospective, randomized, double-blind, placebo-controlled, parallel group study to examine if dipyridamole and/or aspirin decreased the rate of thrombosis of expanded polytetrafluoroethylene (ePTFE) grafts in HD patients. Two patient groups were studied: Type I--with a new ePTFE graft; and Type II--with thrombectomy and/or revision of a previously placed ePTFE graft. One hundred and seven patients were followed for 18 months or until the first thrombotic episode. Actuarial analysis of Type I patients showed cumulative thrombosis rates (mean +/- SEM) of 21 +/- 9% on dipyridamole alone, compared with 25 +/- 11% on dipyridamole and aspirin combination, 42 +/- 13% on placebo, and 80 +/- 12% on aspirin alone. The relative risk of thrombosis with dipyridamole was 0.35 (P = 0.02) and that for aspirin was 1.99 (P = 0.18). In Type II patients, the rate of thrombosis was high in all study drug and placebo groups (overall 78% thrombosis) and actuarial analysis was not carried out because of the small number of patients enrolled. We conclude that dipyridamole is beneficial in patients with new ePTFE grafts and that aspirin does not improve the risk of thrombosis in ePTFE grafts. Neither dipyridamole nor aspirin has any beneficial effect in patients with prior thrombosis of ePTFE grafts. To evaluate the clinical effect and restenosis rate of antiplatelet therapy following peripheral artery angioplasty and stenting.
                After successful placement of peripheral artery stents to 103 patients with peripheral arterial occlusive disease (PAOD) in were randomized assigned to 2 groups: antiplatelet therapy group receiving clopidogrel 75 mg plus aspirin 100 mg (n = 56) and control group (n = 47) receiving anticoagulation therapy low molecular weight heparin (LWMH) for 7 d plus long-term warfarin. The patients were followed up 1 day, and 1, 6, 12, and 18 months after the operation to undergo color Doppler ultrasonography, and examinations of blood routine, bleeding time, coagulation time, and ankle-brachial Index. The primary endpoint events included major bleeding rate, and composite rate of restenosis and reocclusion. The secondary endpoint events included cardiovascular events, death, and adverse drug reaction.
                There were no significant differences in the baseline data between these two groups. The thrombotic occlusion rate was 1.8% in the antiplatelet group and 0% in control group, and the restenosis rate was 14.3% in the antiplatelet group and 25.5% in control group (both P > 0.05). The bleeding complication rate of the antiplatelet group was 1.8%, significantly lower than that of the anticoagulation group (19.1%, P < 0.01). There were not significant differences in cardiovascular event rate and mortality 18 months after operation between these two groups.
                Antiplatelet therapy combined with clopidogrel plus aspirin is effective and safe in preventing restenosis following peripheral artery angioplasty and stenting. To determine the effects of antiplatelet therapy among patients at high risk of occlusive vascular events.
                Collaborative meta-analyses (systematic overviews).
                Randomised trials of an antiplatelet regimen versus control or of one antiplatelet regimen versus another in high risk patients (with acute or previous vascular disease or some other predisposing condition) from which results were available before September 1997. Trials had to use a method of randomisation that precluded prior knowledge of the next treatment to be allocated and comparisons had to be unconfounded-that is, have study groups that differed only in terms of antiplatelet regimen.
                287 studies involving 135 000 patients in comparisons of antiplatelet therapy versus control and 77 000 in comparisons of different antiplatelet regimens.
                "Serious vascular event": non-fatal myocardial infarction, non-fatal stroke, or vascular death.
                Overall, among these high risk patients, allocation to antiplatelet therapy reduced the combined outcome of any serious vascular event by about one quarter; non-fatal myocardial infarction was reduced by one third, non-fatal stroke by one quarter, and vascular mortality by one sixth (with no apparent adverse effect on other deaths). Absolute reductions in the risk of having a serious vascular event were 36 (SE 5) per 1000 treated for two years among patients with previous myocardial infarction; 38 (5) per 1000 patients treated for one month among patients with acute myocardial infarction; 36 (6) per 1000 treated for two years among those with previous stroke or transient ischaemic attack; 9 (3) per 1000 treated for three weeks among those with acute stroke; and 22 (3) per 1000 treated for two years among other high risk patients (with separately significant results for those with stable angina (P=0.0005), peripheral arterial disease (P=0.004), and atrial fibrillation (P=0.01)). In each of these high risk categories, the absolute benefits substantially outweighed the absolute risks of major extracranial bleeding. Aspirin was the most widely studied antiplatelet drug, with doses of 75-150 mg daily at least as effective as higher daily doses. The effects of doses lower than 75 mg daily were less certain. Clopidogrel reduced serious vascular events by 10% (4%) compared with aspirin, which was similar to the 12% (7%) reduction observed with its analogue ticlopidine. Addition of dipyridamole to aspirin produced no significant further reduction in vascular events compared with aspirin alone. Among patients at high risk of immediate coronary occlusion, short term addition of an intravenous glycoprotein IIb/IIIa antagonist to aspirin prevented a further 20 (4) vascular events per 1000 (P<0.0001) but caused 23 major (but rarely fatal) extracranial bleeds per 1000.
                Aspirin (or another oral antiplatelet drug) is protective in most types of patient at increased risk of occlusive vascular events, including those with an acute myocardial infarction or ischaemic stroke, unstable or stable angina, previous myocardial infarction, stroke or cerebral ischaemia, peripheral arterial disease, or atrial fibrillation. Low dose aspirin (75-150 mg daily) is an effective antiplatelet regimen for long term use, but in acute settings an initial loading dose of at least 150 mg aspirin may be required. Adding a second antiplatelet drug to aspirin may produce additional benefits in some clinical circumstances, but more research into this strategy is needed. The clinical benefit of coronary-artery stenting performed in conjunction with coronary angioplasty is limited by the risk of thrombotic occlusion of the stent as well as hemorrhagic and vascular complications of intensive anticoagulation. We compared antiplatelet therapy with conventional anticoagulant therapy with respect to clinical outcomes 30 days after coronary-artery stenting.
                After successful placement of Palmaz-Schatz coronary-artery stents, 257 patients were randomly assigned to receive antiplatelet therapy (ticlopidine plus aspirin) and 260 to receive anticoagulant therapy (intravenous heparin, phenprocoumon, and aspirin). The primary cardiac end point was a composite measure reflecting death from cardiac causes or the occurrence of myocardial infarction, aortocoronary bypass surgery, or repeat angioplasty. The primary noncardiac end point comprised death from noncardiac causes, cerebrovascular accident, severe hemorrhage, and peripheral vascular events.
                Of the patients assigned to antiplatelet therapy, 1.6 percent reached a primary cardiac end point, as did 6.2 percent of those assigned to anticoagulant therapy (relative risk, 0.25; 95 percent confidence interval, 0.06 to 0.77). With antiplatelet therapy, there was an 82 percent lower risk of myocardial infarction than in the anticoagulant-therapy group, and a 78 percent lower need for repeat interventions. Occlusion of the stented vessel occurred in 0.8 percent of the antiplatelet-therapy group and in 5.4 percent of the anticoagulant-therapy group (relative risk, 0.14; 95 percent confidence interval, 0.02 to 0.62). A primary noncardiac end point was reached by 1.2 percent of the antiplatelet-therapy group and 12.3 percent of the anticoagulant-therapy group (relative risk, 0.09; 95 percent confidence interval, 0.02 to 0.31). Hemorrhagic complications occurred only in the anticoagulant-therapy group (in 6.5 percent). An 87 percent reduction in the risk of peripheral vascular events was observed with antiplatelet therapy.
                As compared with conventional anticoagulant therapy, combined antiplatelet therapy after the placement of coronary-artery stents reduces the incidence of both cardiac events and hemorrhagic and vascular complications. 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 prospective, double-blind, randomized 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 standard 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.
Antiplatelet therapy with aspirin had a slight beneficial effect on the patency of peripheral bypass grafts but seemed to have an inferior effect on venous graft patency compared with artificial grafts. The effect of aspirin on cardiovascular outcomes and survival was small and not statistically significant. This might be due to the fact that the majority of patients receiving a peripheral graft have an advanced stage of PAD with critical ischaemia. They are usually seriously ill as a result of cardiovascular disease and have high mortality rates, of 20% per year. Additionally, the number of patients included in this analysis might be too small to reach a statistically significant effect for mortality and cardiovascular morbidity.