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 .
Comparison of two levels of anticoagulant therapy in patients with substitute heart valves.
After cardiac valve replacement patients were blindly r and omized into two groups , both receiving aspirin ( 330 mg ) and dipyridamole ( 75 mg ) twice daily and the oral anticoagulant acenocoumarol ( Sintrom ) . An international normalized ratio of 2.0 to 2.99 was assigned to group A and 3.0 to 4.5 to group B ; both groups were subsequently analyzed for thromboembolic and hemorrhagic complications .  Final evaluation included 51 and 48 patients , respectively . The follow-up was 626 months for group A ( 12.3 months/patient ) and 486 months for group B ( 10.1 months/patient ) . The frequency of thromboembolism was equal in both groups : one transient ischemic attack in group A ( a rate of 1.92/100 patient-years ) and two transient ischemic attacks in group B ( a rate of 4.94/100 patient-years ) . There was , however , a statistical difference in bleeding complications between the two groups ( p less than 0.02 ) . Two patients bled in group A , a rate of 3.9 % ( 3.8/100 patient-years ) , which represents an incidence of one episode each 25.6 years of treatment ; 10 patients bled in group B , a rate of 20.8 % ( 24.7/100 patient-years ) representing an incidence of one episode each 4 years of treatment . We conclude that an international normalized ratio of 2 to 3 is safer than a ratio of 3 to 4.5 and confers good protection from thromboembolism when oral anticoagulant therapy is used conjointly with platelet function-inhibiting drugs in patients with mechanical substitute heart valves
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 .