MONITORING OF LOW-MOLECULAR-WEIGHT HEPARINS IN CARDIOVASCULAR-DISEASE

Thrombin generation is a key event in the pathophysiology of coronary syndromes and provides the rationale for treatment with anticoagulants . Unlike standard heparin, low-molecular-weight heparin (LMWH) has lit tle effect on activated partial thromboplastin time. LMWH treatment ha s been monitored by measurement of anti-Factor Xa activity, but this m ay not accurately reflect the anticoagulant action because LMWHs also inhibit factor II. The Heptest is a clotting assay that is sensitive t o both anti-Xa and anti-IIa activity, as well as inhibition of the ext rinsic pathway by LMWH-stimulated release of tissue factor pathway inh ibitor. The plasma thrombin neutralization assay has also been used to measure LMWH and to detect low concentrations to which chromogenic as says are insensitive, In the clinical setting, monitoring the anti-Xa activity in patients treated with LMWH after acute deep vein thrombosi s offered no advantages over a standard weight-adjusted dose. Moreover , in acute coronary syndromes there is no increase in major hemorrhage rates with weight-adjusted LMWH. Monitoring of LMWH concentrations ma y be advisable in the presence of comorbid conditions carrying an incr eased risk of hemorrhage, such as renal disease, advanced age, severe over- or underweight, or a history of previous bleeding episodes. (C) 1998 by Excerpta Medica, Inc.