HEPARIN INFUSION FACILITATES EX-VIVO SPONTANEOUS PLATELET-AGGREGATIONIN PATIENTS WITH ACUTE MYOCARDIAL-INFARCTION WHO HAVE UNDERGONE THROMBOLYTIC THERAPY

We investigated ex vivo spontaneous platelet aggregation (SPA) in plat elet-rich plasma in 37 patients with acute myocardial infarction. It o ccurred in about 50% of subjects receiving heparin after streptokinase treatment, while it rarely took place in patients who did not receive either streptokinase or heparin and in those treated with streptokina se alone. The study of patients receiving heparin for deep vein thromb osis suggested that SPA may derive from adenosine diphosphate released from platelets during sample handling. We suggest that heparin infusi on may facilitate ex vivo platelet activation and that this mechanism is operative in patients with acute myocardial infarction who have und ergone thrombolytic therapy.