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Tuesday, October 16, 2007

Cochrane review: anticoagulants better than antiplatelets for stroke prevention in AF patients.

According to a Cochrane review,adjusted-dose warfarin and related oral anticoagulants are superior to antiplatelets in the prevention of stroke and major vascular events in patients with non-valvular atrial fibrillation (AF).

The authors of the review note that non-valvular AF ‘carries an increased risk of stroke mediated by embolism of stasis-precipitated thrombi originating in the left atrial appendage’. Although both oral anticoagulants and antiplatelets have proven effective for stroke prevention in most patients at high risk for vascular events, they sought to separately characterise their relative effects in primary stroke prevention, i.e. in those patients without a history of stroke or transient ischaemic attack (TIA).

The authors carried out a comprehensive search of the literature and located eight relevant RCTs (n=9,598) comparing long-term (more than four weeks) adjusted-dose oral anticoagulant treatment to antiplatelet therapy in patients with chronic non-valvular AF and no history of stroke or TIA. The trials included were: ACTIVE W; AFASAK 1; AFASAK II; ATHENS; NASPEAF; PATAF; SPAF IIa and SPAF IIb. All trials used warfarin as the oral anticoagulant except NASPEAF (acenocumarol) and PATAF (several oral anticoagulants including warfarin). Aspirin was the antiplatelet agent tested (75-325mg/day), except ACTIVE W (combination of aspirin plus clopidogrel) and NASPEAF (triflusal).

Oral anticoagulants were associated with lower risk of all stroke (odds ratio (OR) 0.68, 95% CI 0.54 to 0.85; p="0.0007"), ischaemic stroke (OR 0.53, 95% CI 0.41 to 0.68; p ≤ 0.00001) and systemic emboli (OR 0.48, 95% CI 0.25 to 0.90).Assuming an estimated annualised rate of stroke of 4% per year on antiplatelet therapy for primary prevention, about 13 strokes (ischaemic and haemorrhagic) and 19 ischaemic strokes (fatal and non-fatal) per year would be prevented for every 1000 AF patients given oral anticoagulants instead of antiplatelet therapy.

No statistically significant differences were observed between the two treatments in terms of disabling or fatal strokes (OR 0.71, 95% CI 0.59 to 1.04), myocardial infarction (OR 0.69, 95% CI 0.47 to 1.01), vascular death (OR 0.93, 95% CI 0.75 to 1.15) or all cause mortality (OR 0.99, 95% CI 0.83 to 1.18). Intracranial haemorrhages (OR 1.98, 95% CI 1.20 to 3.28; p="0.008") were increased by oral anticoagulant therapy.

Cochrane Database of Systematic Reviews 2007, issue 3 Link to abstract
Ann Int Med (NeLM)

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