82956
document
Warfarin versus aspirin for prevention of thromboembolism in atrial fibrillation : Stroke Prevention in Atrial Fibrillation II Study . Warfarin is an established treatment for prevention of ischaemic stroke in patients with atrial fibrillation , but the value of this agent relative to aspirin in unclear . In the first Stroke Prevention in Atrial Fibrillation ( SPAF-I ) study , direct comparison of warfarin with aspirin was limited by the small number of thromboembolic events . SPAF-II aims to address this issue and also to assess the differential effects of the two treatments according to age . We compared warfarin ( prothrombin time ratio 1.3-1.8 , international normalised ratio 2.0-4.5 ) with aspirin 325 mg daily for prevention of ischaemic stroke and systemic embolism ( primary events ) in two parallel randomised trials involving 715 patients aged 75 years or less and 385 patients older than 75 ; we sought reductions in the absolute rate of primary events by warfarin compared with aspirin of 2 % per year and 4 % per year , respectively . In the younger patients , warfarin decreased the absolute rate of primary events by 0.7 % per year ( 95 % CI-0.4 to 1.7 ) . The primary event rate per year was 1.3 % with warfarin and 1.9 % with aspirin ( relative risk [ RR ] 0.67 , p = 0.24 ) . The absolute rate of primary events in low-risk younger patients ( without hypertension , recent heart failure , or previous thromboembolism ) on aspirin was 0.5 % per year ( 95 % CI 0.1 to 1.9 ) . Among older patients , warfarin decreased the absolute rate of primary events by 1.2 % per year ( 95 % CI-1.7 to 4.1 ) . The primary event rate per year was 3.6 % with warfarin and 4.8 % with aspirin ( RR 0.73 , p = 0.39 ) . In this older group , the rate of all stroke with residual deficit ( ischaemic or haemorrhagic ) was 4.3 % per year with aspirin and 4.6 % per year with warfarin ( RR 1.1 ) . Warfarin may be more effective than aspirin for prevention of ischaemic stroke in patients with atrial fibrillation , but the absolute reduction in stroke rate by warfarin is small . Younger patients without risk factors had a low rate of stroke when treated with aspirin . In older patients the rate of stroke ( ischaemic and haemorrhagic ) was substantial , irrespective of which agent was given . Patient age and the inherent risk of thromboembolism should be considered in the choice of antithrombotic prophylaxis for patients with atrial fibrillation .
82957
Intervention_Pharmacological
Warfarin
82958
Intervention_Pharmacological
aspirin
82959
Intervention_Pharmacological
Warfarin
82960
Intervention_Pharmacological
warfarin
82961
Intervention_Pharmacological
aspirin
82962
Intervention_Pharmacological
warfarin
82963
Intervention_Pharmacological
aspirin 325 mg daily
82964
Intervention_Pharmacological
warfarin
82965
Intervention_Pharmacological
aspirin
82966
Intervention_Pharmacological
warfarin
82967
Intervention_Pharmacological
warfarin
82968
Intervention_Pharmacological
aspirin
82969
Intervention_Pharmacological
aspirin
82970
Intervention_Pharmacological
warfarin
82971
Intervention_Pharmacological
warfarin
82972
Intervention_Pharmacological
aspirin
82973
Outcome_Physical
thromboembolism
82974
Outcome_Physical
ischaemic stroke
82975
Outcome_Physical
systemic embolism
82976
Outcome_Physical
absolute rate of primary events
82977
Outcome_Physical
primary event rate per year
82978
Outcome_Physical
rate of all stroke with residual deficit
82979
Outcome_Physical
ischaemic stroke
82980
Outcome_Physical
rate of stroke
82981
Participant_Condition
atrial fibrillation
82982
Participant_Sample-size
715
82983
Participant_Age
75 years or less
82984
Participant_Sample-size
385
82985
Participant_Age
older than 75