Evaluation of the anticoagulant effect of vitamin K antagonists in patients with non-valvular atrial fibrilation
2019
Background/Aim. Despite the introduction of new oral anticoagulants
(dabigatran, rivoroxaban, apixaban), vitamin K antagonists (VKA), such as
warfarin and acenocoumarol are still the most widely used oral
anticoagulants for the treatment of non-valvular atrial fibrillation (NVAF).
Time in therapeutic range (TTR) represents a measure of the quality of the
anticoagulant effect of these drugs, and it is considered that the lower
value of TTR is associated with the adverse effects of therapy. The study
aim was to evaluate of the effectiveness of VKA therapy in patients with
NVAF and to identify factors affecting the anticoagulation efficacy.
Methods. A retrospective study was conducted on a population of 725
outpatients with NVAF, treated with VKA and followed in Blood Transfusion
Institute of Nis from January to December 2017. Laboratory control of the
INR was done from capillary blood of patients on Thrombotrack Solo (Axis
Shield, Norway) and Thrombostat (Behnk Elektronik, Germany). Targeted
therapeutic INR was between 2.0 and 3.0. For each patient we evaluated all
available INR values to calculate the individual TTR according to the
Rosendaal method. Results. The study included a total of 725 patients with
NVAF which had 6105 INR measurements, what is 8.13±2.47 INR measurements per
patient. The mean value of TTR and was 60.15±17.52%, but 49.72% of patients
had a TTR less than 60%. Patients were at high risk of thrombosis in 6.15%
of time (INR 4.5). The
most significant independent factors affecting the quality of VKA therapy
are gender, arterial hypertension, diabetes mellitus and the use of
amiodarone and antiplatelet drugs (aspirin, clopidogrel). Conclusion. The
TTR is undoubtedly useful indicator of the effectiveness of VKA treatment.
The most important predictors of poorer efficacy of VKA therapy are arterial
hypertension, diabetes mellitus, patints' gender and the use of amiodarone
and antiplatelet (aspirin, clopidogrel) drugs. To improve the quality of VKA
therapy, education of patient and better collaboration with them, as well as
a successful teamwork with clinicians are also imperative. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 175061, Grant no. 43012 and Grant no. 41004]
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