Platelet Survival, Fibrinolytic Activity, Antithrombin III (AT III) Level and Fibrinogen Survival in Venous Thromboembolism (VTE)

 

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Reduced platelet survival has been found in patients who have reccurrent VTE despite anticoagulant treatment, impaired fibrinolytic activity has been found in patients with recurrent VTE, and a reduced AT III level occurs in some families with VTE. This has led to the use of drugs which correct these abnormalities in patients with VTE. However, the incidence of these, and other, abnormalities of hemostasis in unselected patients with VTE is not known. We have measured 51 Cr-platelet survival, euglobulin lysis time (ELT) before and after venous tourniquet occlusion, antiplasmin activity, AT III level, and 125 I-fibrinogen survival in 57 patients documented by venography (49 patients) or lung scan (8 patients). All studies were done off treatment and at least 3 months after the most recent episode of VTE. The mean platelet half-time in patients was similar to the in 42 controls, but 7 patients with VTE (12%) had a reduced platelet half-time. The ELT was significantly longer (p < 0.005), before and after tourniquet occlusion, than in 89 controls. Thus, 40% of patients and only 10% of controls had a ELT longer than 240 minutes after tourniquet occlusion. AT III levels were normal, as was fibrinogen survival. An elevated antiplasmin level was found in one patient in this study and in two others studied while still under treatment with anticoagulants-all 3 had thromboembolic pulmonary hypertension. Abnormalities occurred with equal frequency in patients with idiopathic or secondary, and single episodes or recurrent VTE. These findings suggest that impaired fibrinolytic activity occurrs frequently in VTE, but that reduced platelet survival is uncommon. High antiplasmin levels may predispose to thromboembolic pulmonary hypertension.