Acceleration of blood coagulation in acute myocardial infarction as demonstrated by the heparin clotting time; effect of dicumarol therapy.

A study of blood coagulation was made on cardiac patients with and without acute myocardial infarction, prior to anticoagulant therapy. The heparin clotting time, an in vitro modification of the heparin tolerance test, was accelerated in 74 per cent (14 out of 19) of the patients with acute myocardial infarction studied within three weeks after the attack. One out of 14 patients without acute myocardial infarction had an accelerated heparin clotting time below 20 minutes, the lower limit of the "normal" range established on the basis of study of over 100 control subjects. The clotting time and platelet count revealed no significant variations. Serial coagulation studies, performed on patients receiving Dicumarol therapy, revealed that the heparin clotting time, which provides a sensitive measure of over-all coagulability, is prolonged as the prothrombin concentration is diminished. The significance of these findings in relation to thromboembolic complications of acute myocardial infarction and anticoagulant therapy is discussed.