The limited importance of factor Xa inhibition to the anticoagulant
property of heparin in thromboplastin-activated plasma
J Pieters and T Lindhout
Department of Biochemistry, University of Limburg, Maastricht, The
Netherlands.
The antifactor Xa activities of heparin fractions are widely used as an ex
vivo index of their antithrombotic efficacy. Its clinical meaning, however,
remains speculative. In the study reported, we measured the effects of
standard heparin, a synthetic pentasaccharide heparin (antifactor Xa
activity only), and a low molecular weight heparin (LMWH) on factor Xa,
factor Va, and thrombin generation in thromboplastin-activated plasma. We
clearly demonstrated that the antifactor Xa activity of heparin contributed
little in its anticoagulant activity. The inhibition of factor Va
generation, dependent on the heparin antithrombin activity only, is of
prime importance to the inhibition of thrombin generation in plasma. The
inhibition of thrombin generation by the LMWH was comparable with that of
standard heparin on the basis of their respective antithrombin specific
activities, but not on the basis of their antifactor Xa activities.
Volume 72,
Issue 6,
pp. 2048-2052,
12/01/1988
Copyright © 1988 by The American Society of Hematology
