Comparative study of antithrombotic effect of a low molecular weight heparin and unfractionated heparin in an ex vivo model of deep arterial injury

Thrombosis after plaque rupture triggers the onset of acute coronary events. The treatment of choice for patients with acute coronary syndromes is conventional unfractionated heparin. Low molecular weight heparin has recently been reported to be as effective and even safer than unfractionated heparin. In this study, the effects of the low molecular weight heparin reviparin and unfractionated heparin on thrombus formation were examined under dynamic conditions using an extracorporeal perfusion chamber in a porcine model. Thrombus formation was assessed by the deposition of porcine ¹²³I-fibrin(ogen) and autologous ¹¹¹In-platelets on porcine tunica media at high and low shear rates. Reviparin reduced the fibrinogen molecules deposited on injured vessels at high shear rates (252±80 molecules×10¹²/cm² for reviparine (200 U/kg/hour) vs. 624±70×10¹²/cm² for unfractionated heparin (200 U/kg/hour) (p<0.05). At low shear rates, fibrinogen deposition was also significantly reduced by reviparin (130±15 molecules×10¹²/cm²) compared to unfractionated heparin (192±40×10¹²/cm² at 200 U/kg/hour; p<0.05). No change in platelet deposition was detected after heparin administration in either treatment group. In conclusion, the low molecular weight heparin reviparin has a higher antithrombotic potential than unfractionated heparin. Reviparin may have advantages over unfractionated heparin in treatment and prevention of acute coronary syndromes.