A lower daily dose of aspirin ( < 100 mg ) may be associated with a lower major bleeding risk than higher doses .
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 .
BACKGROUND Patients with prosthetic heart valves are at increased risk for valve thrombosis and arterial thromboembolism .
Oral anticoagulation alone , or the addition of antiplatelet drugs , has been used to minimise this risk .
An important issue is the effectiveness and safety of the latter strategy .
OBJECTIVES This is an up date of our previous review ; the goal was to create a valid synthesis of all available , method ologically sound data to further assess the safety and efficacy of combined oral anticoagulant and antiplatelet therapy versus oral anticoagulant monotherapy in patients with prosthetic heart valves .
Trial of combined warfarin plus dipyridamole or aspirin therapy in prosthetic heart valve replacement: danger of aspirin compared with dipyridamole.
Despite the use of oral anticoagulation in patients with prosthetic heart valves , persistent thromboembolism over time warrants a search for improved methods of prevention . Thus , patients receiving 1 or more mechanical prosthetic heart valves were r and omized to therapy with warfarin plus dipyridamole ( 400 mg/day ) or warfarin plus aspirin ( 500 mg/day ) on the basis of location and type of valve and surgeon , and followed up with a concurrent , nonr and omized control group taking warfarin alone . In 534 patients followed up 1,319 patient-years ,  excessive bleeding ( necessitating blood transfusion or hospitalization ) was noted in the warfarin plus aspirin group ( 23 of 170 [ 14 % ] , or 6.0/100 patient-years ) compared with warfarin plus dipyridamole ( 7 of 181 [ 4 % ] , or 1.6/100 patient-years , p less than 0.001 ) , or warfarin alone ( 9 of 183 [ 5 % ] , or 1.8/100 patient-years , p less than 0.001 ) . A trend was evident toward a reduction in thromboembolism in the warfarin plus dipyridamole group ( 2 of 181 [ 1 % ] , or 0.5/100 patient-years ) as compared with warfarin plus aspirin ( 7 of 170 [ 4 % ] , or 1.8/100 patient-years ) , or warfarin alone ( 6 of 183 [ 4 % ] , or 1.2/100 patient-years ) . Adequacy of anticoagulation ( based on 12,720 prothrombin time determinations ) was similar in all 3 groups with 65 % of prothrombin times in the therapeutic range ( 1.5 less than or equal to prothrombin time/control less than or equal to 2.5 ) , 30 % too low , and 5 % too high . Warfarin plus aspirin therapy result ed in excessive bleeding and is contraindicated . Longer follow-up study is needed to determine whether further separation of the incidence of thromboembolism can be detected
A lower daily dose of aspirin ( < 100 mg ) may be associated with a lower major bleeding risk than higher doses .
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 .
BACKGROUND Patients with prosthetic heart valves are at increased risk for valve thrombosis and arterial thromboembolism .
Oral anticoagulation alone , or the addition of antiplatelet drugs , has been used to minimise this risk .
An important issue is the effectiveness and safety of the latter strategy .
OBJECTIVES This is an up date of our previous review ; the goal was to create a valid synthesis of all available , method ologically sound data to further assess the safety and efficacy of combined oral anticoagulant and antiplatelet therapy versus oral anticoagulant monotherapy in patients with prosthetic heart valves .