Effect of heparin and enoxaparin on platelet interaction with fibrin clots.

It has been recently shown that platelet-rich thrombi are particularly resistant to thrombolysis. Since unfractionated heparin was reported to enhance fibrinogen binding to platelets responsible for the hyperaggregating effect of this drug, the purpose of this work was to determine whether or not heparin could also modulate platelet interaction to whole blood clot. We have therefore investigated the retention to a standard clot of 111In-labelled platelets suspended in plasma in presence of saline (control), heparin or a low molecular weight heparin (Enoxaparin). We have shown that the platelet interaction to the clot was significantly increased by heparin but not by enoxaparin used at the same anti Xa activity. In conclusion, this difference may favor the use of enoxaparin over heparin in clinical situation associated with platelet retention to fibrin clot, such as thrombolysis.