To evaluate the effect of antithrombotic therapy, serial changes in platelet aggregability were investigated in 103 patients who had received heart valve replacement. All patients received warfarin and were divided into three groups: warfarin alone (control), and combined with trapidil and dipyridamole. Both antithrombogenic drugs were given at a dose of 300 mg/day. Platelet count and aggregation were evaluated out every three months for 36 months.
Antiplatelet drugs had no affect on the platelet count during the course. The platelet aggregation did not change in the control group, but were decreased at 24 and 30 months in the trapidil group and 24 months in the dipyridamole group. The platelet aggregation was significantly suppressed by trapidil compared to the control at 30 months. The incidence of thromboembolism in control, trapidil and dipyridamole groups was 9.0%, 4.3% and 7.7% respectively. These results indicate that anti-platelet drugs given with warfarin are safe and effective for patients with a prosthetic valve to prevent thromboembolism.