Low-dose aspirin combined with dipyridamole versus anticoagulants after femoropopliteal percutaneous transluminal angioplasty. Low-intensity oral anticoagulation plus low-dose aspirin versus high-intensity oral anticoagulation alone: a randomized trial in patients with mechanical prosthetic heart valves. Antiplatelet drugs in femoropopliteal vein bypasses: a multicenter trial. Clopidogrel plus aspirin versus oral anticoagulation for atrial fibrillation in the Atrial fibrillation Clopidogrel Trial with Irbesartan for prevention of Vascular Events (ACTIVE W): a randomised controlled trial. Comparative effects of antiplatelet, anticoagulant, or combined therapy in patients with valvular and nonvalvular atrial fibrillation: a randomized multicenter study. Primary prevention of arterial thromboembolism in non-rheumatic atrial fibrillation in primary care: randomised controlled trial comparing two intensities of coumarin with aspirin. Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients. Intensifying platelet inhibition with tirofiban in poor responders to aspirin, clopidogrel, or both agents undergoing elective coronary intervention: results from the double-blind, prospective, randomized Tailoring Treatment with Tirofiban in Patients Showing Resistance to Aspirin and/or Resistance to Clopidogrel study. Random control trial of a short course of aspirin and dipyridamole (Persantin) for femorodistal grafts.
To investigate whether anticoagulation or platelet inhibition treatment provides better prevention of reobstruction after percutaneous transluminal angioplasty (PTA).
                In a controlled study, 160 patients received either oral anticoagulants or a combination of low-dose acetylsalicylic acid (25 mg) and dipyridamole (200 mg) (ASAD) twice daily for 1 year after successful femoropopliteal PTA. Compliance was comparable. The patients in the two groups had similar clinical and angiographic characteristics. Patency was assessed with noninvasive methods 1 day and then 3, 6, and 12 months after PTA and was confirmed at angiography at the end of the study in 112 patients.
                Patency in patients who received anticoagulants was 53% and was not statistically significantly different from 69% in patients who received ASAD (P = .18). With anticoagulants, there were four bleeding complications (one was fatal); with ASAD, only five minor complications occurred.
                ASAD is at least as effective as anticoagulants for secondary prevention of obstruction after PTA but has less severe side effects. Mechanical heart valve replacement requires lifelong anticoagulant treatment. Aspirin has proved useful in further reducing thromboembolic events when added to oral anticoagulants. However, increased (gastrointestinal) bleeding was observed at the doses previously tested for this combination in heart valve prostheses.
                We performed a prospective randomized trial to compare the combination of low-intensity oral anticoagulants (international normalized ratio 2.5 to 3.5) plus aspirin (100 mg/day) (arm A) versus high-intensity oral anticoagulants alone (arm B) (international normalized ratio 3.5 to 4.5). Arm A included 258 patients and arm B 245 patients. The two groups were comparable for all baseline characteristics.
                The outcomes of the study were embolism, valve thrombosis, and major hemorrhage. The median follow-up was 23 months. The two treatments offered similar antithrombotic protection. The incidence of embolic episodes was 1.32 per 100 patient-years (95% confidence interval 0.53 to 2.7) for arm A and 1.48 per 100 patient-years (95% confidence interval 0.59 to 3.03) for arm B. Major hemorrhage occurred in 1.13 per 100 patient-years (95% confidence interval 0.41 to 2.45) for arm A and 2.33 per 100 patient-years (95% confidence interval 1.17 to 4.14) for arm B. Gastrointestinal bleeding was not increased by this combined reduced dose of aspirin and coumarin. 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 anticoagulation therapy reduces risk of vascular events in patients with atrial fibrillation. However, long-term monitoring is necessary and many patients cannot achieve optimum anticoagulation. We assessed whether clopidogrel plus aspirin was non-inferior to oral anticoagulation therapy for prevention of vascular events.
                Patients were enrolled if they had atrial fibrillation plus one or more risk factor for stroke, and were randomly allocated to receive oral anticoagulation therapy (target international normalised ratio of 2.0-3.0; n=3371) or clopidogrel (75 mg per day) plus aspirin (75-100 mg per day recommended; n=3335). Outcome events were adjudicated by a blinded committee. Primary outcome was first occurrence of stroke, non-CNS systemic embolus, myocardial infarction, or vascular death. Analyses were by intention-to-treat. This study is registered with ClinicalTrials.gov, number NCT00243178.
                The study was stopped early because of clear evidence of superiority of oral anticoagulation therapy. There were 165 primary events in patients on oral anticoagulation therapy (annual risk 3.93%) and 234 in those on clopidogrel plus aspirin (annual risk 5.60%; relative risk 1.44 (1.18-1.76; p=0.0003). Patients on oral anticoagulation therapy who were already receiving this treatment at study entry had a trend towards a greater reduction in vascular events (relative risk 1.50, 95% CI 1.19-1.89) and a significantly (p=0.03 for interaction) lower risk of major bleeding with oral anticoagulation therapy (1.30; 0.94-1.79) than patients not on this treatment at study entry (1.27, 0.85-1.89 and 0.59, 0.32-1.08, respectively).
                Oral anticoagulation therapy is superior to clopidogrel plus aspirin for prevention of vascular events in patients with atrial fibrillation at high risk of stroke, especially in those already taking oral anticoagulation therapy. This trial evaluated the efficacy and safety of the combination of antiplatelet and moderate-intensity anticoagulation therapy in patients with atrial fibrillation associated with recognized risk factors or mitral stenosis.
                Warfarin was more effective than aspirin in preventing stroke in these patients; combined therapy with low anticoagulant intensity was ineffective. Mitral stenosis patients were not investigated.
                We performed a multicenter randomized trial in 1,209 patients at risk. The intermediate-risk group included patients with risk factors or age >60 years: 242 received the cyclooxygenase inhibitor triflusal, 237 received acenocumarol, and 235 received a combination of both. The high-risk group included patients with prior embolism or mitral stenosis: 259 received anticoagulants and 236 received the combined therapy. Median follow-up was 2.76 years. Primary outcome was a composite of vascular death and nonfatal stroke or systemic embolism.
                Primary outcome was lower in the combined therapy than in the anticoagulant arm in both the intermediate- (hazard ratio [HR] 0.33 [95% confidence interval (CI)0.12 to 0.91]; p = 0.02) and the high-risk group (HR 0.51 [95% CI 0.27 to 0.96]; p = 0.03). Primary outcome plus severe bleeding was lower with combined therapy in the intermediate-risk group. Nonvalvular and mitral stenosis patients had similar embolic event rates during anticoagulant therapy.
                The combined antiplatelet plus moderate-intensity anticoagulation therapy significantly decreased the vascular events compared with anticoagulation alone and proved to be safe in atrial fibrillation patients. To investigate the effectiveness of aspirin and coumarin in preventing thromboembolism in patients with non-rheumatic atrial fibrillation in general practice.
                Randomised controlled trial.
                729 patients aged >/=60 years with atrial fibrillation, recruited in general practice, who had no established indication for coumarin. Mean age was 75 years and mean follow up 2. 7 years.
                Primary care in the Netherlands.
                Patients eligible for standard intensity coumarin (international normalised ratio 2.5-3.5) were randomly assigned to standard anticoagulation, very low intensity coumarin (international normalised ratio 1.1-1.6), or aspirin (150 mg/day) (stratum 1). Patients ineligible for standard anticoagulation were randomly assigned to low anticoagulation or aspirin (stratum 2).
                Stroke, systemic embolism, major haemorrhage, and vascular death.
                108 primary events occurred (annual event rate 5.5%), including 13 major haemorrhages (0.7% a year). The hazard ratio was 0.91 (0.61 to 1.36) for low anticoagulation versus aspirin and 0.78 (0.34 to 1.81) for standard anticoagulation versus aspirin. Non-vascular death was less common in the low anticoagulation group than in the aspirin group (0.41, 0.20 to 0.82). There was no significant difference between the treatment groups in bleeding incidence. High systolic and low diastolic blood pressure and age were independent prognostic factors.
                In a general practice population (without established indications for coumarin) neither low nor standard intensity anticoagulation is better than aspirin in preventing primary outcome events. Aspirin may therefore be the first choice in patients with atrial fibrillation in general practice. 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. Inhibition of platelet aggregation after aspirin or clopidogrel intake varies greatly among patients, and previous studies have suggested that poor response to oral antiplatelet agents may increase the risk of thrombotic events, especially after coronary angioplasty. Whether this reflects suboptimal platelet inhibition per se, which might benefit from more potent antiplatelet agents such as tirofiban, is unknown.
                We screened 1277 patients to enroll 93 aspirin, 147 clopidogrel, and 23 dual poor responders, based on a point-of-care assay, who underwent elective coronary angioplasty at 10 European sites for stable or low-risk unstable coronary artery disease. Patients were randomly assigned in a double-blind manner to receive either tirofiban (n=132) or placebo (n=131) on top of standard aspirin and clopidogrel therapy. The primary end point, consisting of troponin I/T elevation at least 3 times the upper limit of normal, was attained in 20.4% (n=27) in the tirofiban group compared with 35.1% (n=46) in the placebo group (relative risk, 0.58; 95% confidence interval, 0.39 to 0.88; P=0.009). The rate of major adverse cardiovascular events within 30 days in the tirofiban group also was reduced (3.8% versus 10.7%; P=0.031). The overall incidence of bleeding was low, likely explained by a substantial use of the transradial approach, and did not differ between the 2 groups.
                In low-risk patients according to clinical presentation who had poor responsiveness to standard oral platelet inhibitors via a point-of-care assay, intensified platelet inhibition with tirofiban lowers the incidence of myocardial infarction after elective coronary intervention. The effect of a short course of anti-platelet agents, started preoperatively, on the patency of femorodistal bypass grafts is unknown. One hundred and forty-eight such grafts were randomized to act as controls or to receive dipyridamole 200 mg b.d. for 48 h pre-operatively and dipyridamole 200 mg b.d. with aspirin 300 mg daily for 6 weeks after surgery. Patients were well-matched and the mean pre-operative pressure index of 0.37 rose to 0.78 during the first postoperative week. No deaths were attributable to the treatment. Ninety-three grafts were autogenous vein and the remainder were prosthetic (GORE-TEX (PTFE), human umbilical vein or externally supported Dacron). At 1 year autogenous vein cumulative patency was 75 per cent. Overall results showed higher patency in the treated group (P = 0.012) which was entirely accounted for by the difference between prosthetic dipyridamole and aspirin group (85 per cent patency) and prosthetic control groups (53 per cent patency, P = 0.005) and arose during the first postoperative month. There were 11 deaths and 8 amputations in the dipyridamole and aspirin group and 8 deaths and 12 amputations in the control group. It is concluded that a six week perioperative course of dipyridamole and aspirin allows the patency of prosthetic femorodistal bypass to approach that of autogenous vein, and the regimen therefore is recommended for patients who may require a prosthetic graft.
Adding antiplatelet therapy, either dipyridamole or low-dose aspirin, to oral anticoagulation decreases the risk of systemic embolism or death among patients with prosthetic heart valves. The risk of major bleeding is increased with antiplatelet therapy. These results apply to patients with mechanical prosthetic valves or those with biological valves and indicators of high risk such as atrial fibrillation or prior thromboembolic events. The effectiveness and safety of low dose aspirin (100 mg daily) appears to be similar to higher dose aspirin and dipyridamole.