Standard heparin but not LMW heparin induces a concomitant increase of t-PA and PAI-1 without modification of global fibrinolysis: study after 60 days treatment.

The relationship between heparin and fibrinolysis is strongly suggested. We have studied the influence on fibrinolysis of standard heparin (SH), Calciparin and low molecular weight heparin (LMWH), Fraxiparin, given preventively in an elderly population. Patients were randomized into two groups (SH, LMWH). We investigated fibrinolytic parameters (ECLT, t-PA antigen, PAI-1 activity and antigen, t-PA/PAI-1 complexes) before treatment (D0) and at D30 and D60, before and after venous occlusion (VO). Values at D0, D30 and D60 were compared within each group. A significant and marked increase in t-PA and t-PA/PAI-1 complexes at D30 and D60 before and after VO was noted only in the SH group. The mechanism and clinical relevance of this increase remains to be established.