The β-blocker heart attack trial: studies of platelets and factor VIII

Serial studies of platelets and factor VIII were performed in 16 patients enrolled in the Beta Blocker Heart Attack Trial. Eight patients received placebo, and eight were treated with propranolol, in doses ranging from 40 to 320 mg per day for periods of from 6 to 31 months. No differences in platelet-collagen affinity, factor VIII coagulant activity, factor VIII related antigen, or ristocetin cofactor activity were observed between treated and untreated patients. However, circulating platelet aggregates, which were initially increased in both groups, significantly declined in those receiving propranolol (p < 0.05). This indicates that customarily used doses of propranolol affect platelet reactivity in vivo.