Patients with recent onset of atrial fibrillation (AF) receive anticoagulation with low-molecular-weight heparin (LMWH) and coumarin targeted at an INR of 2 to 3. Recently, LMWH is given alone before cardioversion followed by coumarin. At present, no method is available to determine the combined effect of LMWH and coumarin in order to get information on the in vivo anticoagulant status of these patients. Patients with recent onset of AF (n=200) received 8.000 IU LMWH certoparin bid upon entry into the study. Phenprocoumon was started after electrical cardioversion. LMWH was stopped after 2 days within therapeutic INR range of phenprocoumon. The clincial data have been published (Clin Res Cardiol 2008). Blood samples were drawn from patients before LMWH administration (visit 1, V1), before start of phenprocoumon (V4) and after reaching the desired INR range and before stopping LMWH (V5) to determine a set of anticoagulant parameters. The study was accepted by the local ethics committees and patients gave written informed consent. Activated partial thromboplastin time, chromogenic factor Xa assay, heptest time values, prothrombinase-induced clotting time and tissue factor pathway inhibitor demonstrated the anticoagulant effect of certoparin at V4 and V5. Results of these parameters differed between V1 and V4 as well as between V1 and V5 (all p<0.001) but not between V4 and V5. Prothrombin time was prolonged at V5 versus V1 and V4 (both p<0.001). D-Dimer and prothrombinfragment F1+2 significantly decreased from V1 to V4 and from V4 to V5 (all p<0.001). Endogenous thrombin potential assay (ETP) was inhibited stronger at V4 compared to V1, and at V5 compared to V4 (both p<0.001). D-Dimer, F1+2 and ETP are the parameters reflecting the combined anticoagulant effect of certoparin and phenprocoumon while overlapping anticoagulation with these compounds in patients with recent AF for electrical cardioversion. The clinical effects on thromboembolic or bleeding incidences remain to be determined.

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