Atrial fibrillation-some current problems

Anticoagulants versus antiplatelet therapy for preventing stroke in patients with nonrheumatic atrial fibrillation and a history of stroke or transient ischemic attack

BACKGROUND

People with nonrheumatic atrial fibrillation (NRAF) who have had a transient ischemic attack (TIA) or minor ischemic stroke are at risk of recurrent stroke. Both warfarin and aspirin have been shown to reduce the recurrence of vascular events.

OBJECTIVES

The objective of this review was to compare the effect of anticoagulants with antiplatelet agents, for secondary prevention, in people with NRAF and previous cerebral ischemia.

SEARCH STRATEGY

We searched the Cochrane Stroke Group trials register (last searched 9 June 2003) and contacted trialists.

SELECTION CRITERIA

Randomised trials comparing oral anticoagulants with antiplatelet agents in patients with NRAF and a previous TIA or minor ischemic stroke.

DATA COLLECTION AND ANALYSIS

Both reviewers extracted and analysed data.

MAIN RESULTS

Two trial were identified. The European Atrial Fibrillation Trial (EAFT) involving 455 patients, who received either anticoagulants (International Normalised Ratio (INR) 2.5 to 4.0), or aspirin (300 mg/day). Patients joined the trial within three months of transient ischemic attack or minor stroke. The mean follow up was 2.3 years. In the Studio Italiano Fibrillazione Atriale (SIFA) trial, 916 patients with NRAF and a TIA or minor stroke within the previous 15 days were randomised to open label anticoagulants (INR 2.0 to 3.5) or indobufen (a reversible platelet cyclooxygenase inhibitor, 100 or 200 mg BID). The follow-up period was one year. The combined results show that anticoagulants were significantly more effective than antiplatelet therapy both for all vascular events (Peto odds ratio (Peto OR) 0.67, 95% confidence interval (CI) 0.50 to 0.91) and for recurrent stroke (Peto OR 0.49, 95% CI 0.33 to 0.72). Major extracranial bleeding complications occurred more often in patients on anticoagulants (Peto OR 5.16, 95% CI 2.08 to 12.83), but the absolute difference was small (2.8% per year versus 0.9% per year in EAFT and 0.9% per year versus 0% in SIFA). Warfarin did not cause a significant increase of intracranial bleeds.

REVIEWERS' CONCLUSIONS

The evidence from two trials suggests that anticoagulant therapy is superior to antiplatelet therapy for the prevention of stroke in people with NRAF and recent non-disabling stroke or TIA. The risk of extracranial bleeding was higher with anticoagulant therapy than with antiplatelet therapy.

Anticoagulants for preventing stroke in patients with nonrheumatic atrial fibrillation and a history of stroke or transient ischaemic attack

BACKGROUND

People with nonrheumatic atrial fibrillation (NRAF) who have had a transient ischaemic attack (TIA) or a minor ischaemic stroke are at high risk of recurrent stroke.

OBJECTIVES

The objective of this review was to assess the effect of anticoagulants for secondary prevention, after a stroke or TIA, in patients with NRAF.

SEARCH STRATEGY

We searched the Cochrane Stroke Group trials register (9 June 2003) and contacted trialists.

SELECTION CRITERIA

Randomised trials comparing oral anticoagulants with control (no therapy) or placebo in people with NRAF and a previous TIA or minor ischaemic stroke. Control groups on aspirin did not meet the selection criteria.

DATA COLLECTION AND ANALYSIS

Both reviewers assessed trial quality and extracted data.

MAIN RESULTS

Two trials involving 485 people were included. Follow-up time was 1.7 years in one trial and 2.3 years in the other. Anticoagulants reduced the odds of recurrent stroke by two-thirds (odds ratio (OR) 0.36, 95% confidence interval (CI) 0.22 to 0.58). The odds of all vascular events was shown to be almost halved by treatment (OR 0.55, 95% CI 0.37 to 0.82). The odds of major extracranial haemorrhage was increased (OR 4.32, 95% CI 1.55 to 12.10). No intracranial bleeds were reported among people given anticoagulants.

REVIEWERS' CONCLUSIONS

The evidence suggests that anticoagulants are beneficial, without serious adverse effects, for people with NRAF and recent cerebral ischaemia.

Anticoagulants versus antiplatelet therapy for preventing stroke in patients with nonrheumatic atrial fibrillation and a history of stroke or transient ischemic attacks

BACKGROUND

People with nonrheumatic atrial fibrillation who have had a transient ischemic attack or minor ischemic stroke are at risk of recurrent stroke.

OBJECTIVES

The objective of this review was to compare the effect of anticoagulants with antiplatelet therapy, for secondary prevention, in people with nonrheumatic atrial fibrillation and previous cerebral ischaemia.

SEARCH STRATEGY

The reviewer searched the Cochrane Stroke Group trials register and contacted trialists.

SELECTION CRITERIA

Randomised trials comparing oral anticoagulants with aspirin in patients with non-rheumatic atrial fibrillation and a previous transient ischaemic attack or minor ischaemic stroke.

DATA COLLECTION AND ANALYSIS

One reviewer extracted the data.

MAIN RESULTS

One trial was included, involving 455 patients. They received either anticoagulants (International Normalised Ratio 2.5 to 4.0), or 300 milligrams of aspirin per day. People joined the trial within three months of transient ischaemic attack or minor stroke. The mean follow-up was 2.3 years. Anticoagulant therapy approximately halved the odds of serious vascular events (odds ratio 0.55, 95% confidence interval 0.36 to 0. 83). This equates to preventing an extra 50 vascular events per year for every 1000 patients treated. Anticoagulant therapy decreased the odds of recurrent stroke by two-thirds (odds ratio 0.35, 95% confidence interval 0.22 to 0.59). This translates to preventing an extra 60 strokes for every 1000 patients treated per year. Major extracranial bleeds occurred more often in patients given anticoagulants (odds ratio 4.65, 95% confidence interval 1.66 to 12.99). The absolute difference was 2.8% versus 0.9% bleeds per year. None of the patients on anticoagulants and one on aspirin had an intracerebral bleed.

REVIEWER'S CONCLUSIONS

The evidence from one trial suggests that anticoagulant therapy can benefit people with nonrheumatic atrial fibrillation and recent cerebral ischaemia. Aspirin may be a useful alternative if there is a contraindication to anticoagulant therapy. The risk of adverse events appears to be higher with anticoagulant therapy than aspirin.

Anticoagulants for preventing stroke in patients with nonrheumatic atrial fibrillation and a history of stroke or transient ischemic attacks

BACKGROUND

People with nonrheumatic atrial fibrillation who have had a transient ischemic attack or a minor ischemic stroke are at risk of recurrent stroke.

OBJECTIVES

The objective of this review was to assess the effect of anticoagulants for secondary prevention, after a stroke or transient ischaemic attack, in patients with nonrheumatic atrial fibrillation.

SEARCH STRATEGY

The reviewer searched the Cochrane Stroke Group trials register and contacted trialists.

SELECTION CRITERIA

Randomised trials comparing oral anticoagulants (target International Normalised Ratio range 2.5 to 4.0) with control or placebo in people with nonrheumatic atrial fibrillation and a previous transient ischaemic attack or minor ischaemic stroke.

DATA COLLECTION AND ANALYSIS

One reviewer assessed trial quality and extracted data.

MAIN RESULTS

Two trials involving 485 people were included. Anticoagulants reduced the risk of recurrent stroke by two-thirds (odds ratio 0.36, 95% confidence interval 0.22 to 0.58). The risk of all vascular events was shown to be almost halved by treatment (odds ratio 0.55, 95% confidence interval 0.37 to 0.82). No intracranial bleeds were reported among people given anticoagulants.

REVIEWER'S CONCLUSIONS

The evidence suggests that anticoagulants are beneficial, without serious adverse effects, for people with nonrheumatic atrial fibrillation and recent cerebral ischaemia.

WITHDRAWN: Antiplatelet therapy for preventing stroke in patients with nonrheumatic atrial fibrillation and a history of stroke or transient ischemic attacks

BACKGROUND

People with nonrheumatic atrial fibrillation who have had a transient ischemic attack or minor ischemic stroke are at risk of recurrent stroke.

OBJECTIVES

The objective of this review was to assess the effect of antiplatelet therapy for secondary prevention in people with nonrheumatic atrial fibrillation and a previous transient ischaemic attack or ischaemic stroke.

SEARCH STRATEGY

The reviewer searched the Cochrane Stroke Group trials register and contacted trialists.

SELECTION CRITERIA

Randomised trials comparing an antiplatelet agent with placebo or open control in people with nonrheumatic atrial fibrillation and a previous transient ischaemic attack or minor ischaemic stroke.

DATA COLLECTION AND ANALYSIS

One reviewer extracted the data.

MAIN RESULTS

One trial was included, in which 300 milligrams of aspirin per day was compared with placebo. This review includes 404 aspirin-treated patients and 378 placebo patients in total. The mean follow-up was 2.3 years. No difference was shown between aspirin and placebo in the annual rate of all vascular events, including vascular death, recurrent stroke (ischaemic or haemorrhagic), myocardial infarction, and systemic embolism. The odds ratio was 0.84, 95% confidence interval 0.63 to 1.14, or 15% of those receiving aspirin versus 19% for those given placebo. Aspirin may prevent 40 vascular events (of all types) per 1000 patients treated for one year. There was a non-significant reduction in the risk of recurrent stroke from 12% to 10% per year (odds ratio 0.89, 95% confidence interval 0.64 to 1.24). The incidence of major bleeding events, requiring hospitalisation, blood transfusion or surgical treatment, was low (0.9% per year for aspirin versus 0.7% for placebo).

AUTHORS' CONCLUSIONS

Aspirin may reduce the risk of vascular events in people with nonrheumatic atrial fibrillation, but the effect shown in the single trial was not statistically significant.

Design of a multicenter randomized trial for the Stroke Prevention in Atrial Fibrillation Study. The Stroke Prevention in Atrial Fibrillation Investigators

Individuals with nonvalvular atrial fibrillation are at increased risk of stroke. The Stroke Prevention in Atrial Fibrillation Study is a 15-center randomized clinical trial examining the risks and benefits of low-intensity warfarin (prothrombin time of 1.3-1.8 times control) and aspirin (325 mg/day) in patients with constant or intermittent atrial fibrillation. Candidates for anticoagulation (group I) are randomized to receive warfarin in an open-label fashion, aspirin, or placebo; the last two treatments are given in a double-blind fashion. Warfarin-ineligible patients (group II) are randomized to receive aspirin or placebo in a double-blind fashion. Primary end points are ischemic stroke and systemic embolism. Secondary end points are death, transient ischemic attack, myocardial infarction, and unstable angina pectoris. Analysis is based on the intention-to-treat principle. The anticipated rate of primary end points in patients receiving placebo is 6%/yr. The sample size of 1,644 patients is based on a projected reduction in the rate of primary end points of 50% by warfarin and of 33% by aspirin (beta = 0.2, alpha = 0.05). Patient entry commenced in June 1987 and will continue for 3 years, with an additional year of follow-up. High-risk subsamples identified by clinical and echocardiographic criteria are sought prospectively.