Purpose: To assess the problem of no need for routine coagulation laboratory monitoring of direct thrombin inhibitors and direct factor Xa inhibitors.
Methods: 52 patients with nonvalvular atrial fibrillation, coronary artery disease and at least one CHA2DS2VASc risk factor were enrolled. Mean CHA2DS2VASc score 4,6, mean HAS-BLED score 2. Exclusion criteria: eGFR < 30 ml/min. 40 patients (18 females and 22 males), receiving dabigatran etexilate bid (75, 110 or 150mg). 12 patients (6 females and 6 males) receiving 15 or 20mg q.d.
Results: Taking into account prescribing information, the laboratory monitoring was not obtained. Sporadic coagulation measurements showed thrombin time significant (at least two-fold) extension at the end of the first week of therapy with dabigatran and in some cases had reached 240 seconds. After a month of therapy some patients had thrombin time at the upper limit of normal. However in several examples it remained about 2-4 fold increased in a dose-dependent manner (dabigatran 150 mg bid). Furthermore, after the first week of therapy the aPTT was prolonged by 1.5-2.2 times in comparison to the initial value and reached the upper limits of normal by the end of the first month. Blood test revealed 14-32% reduction in platelet count compared to baseline (up to 52% in one patient). These phenomena appeared to be dose-independent.
Conclusions: At present, due to the lack of recommendations the anticoagulation monitoring is not carried out. In most cases, doctors had no information on real changes in blood coagulation. Further studies are necessary to find the affordable algorithm for the monitoring of long-term anticoagulation therapy. Interaction with other pharmacological agents (especially with anti-arrhythmic drugs) should be specified.