Recombinant t-PA and platelet activity

Platelet-rich coronary arterial occlusions are relatively resistant to thrombolysis with recombinant tissue-type plasminogen activator, or rt-PA, while erythrocyte-rich thrombi are lysed at low doses. The combined administration of rt-PA with a platelet antagonist enhances thrombolysis and can prevent reocclusion, which suggests that platelet activation predominates during thrombus formation and after thrombolysis. In addition to direct effects on platelet activity, rt-PA also acts indirectly through generation of plasmin, which degrades fibrin.