Inadequacy of Vitamin K Antagonist Use in Patients with Atrial Fibrillation – Overview of Everyday Clinical Practice at the Merkur University Hospital in Zagreb, Croatia

Atrial fibrillation is the most common cardiac arrhythmia. It increases the risk of death and thromboembolic events. Vitamin K antagonists reduce these risks. Disadvantages of vitamin K antagonist therapy are narrow therapeutic range and interactions with drugs and food. In a single center prospective study, we enrolled 249 patients with atrial fibrillation over a 12-month period. The aim of our study was to evaluate vitamin K antagonist use regarding the indication and adequate dose. Data on 249 consecutive patients with atrial fibrillation were collected before general availability of novel oral anticoagulants. Out of 249 patients, 160 (64.2%) had indication for oral anticoagulant therapy. Only 81 (50.6%) patients had vitamin K antagonist in therapy, 12 (14.8%) of them in adequate dose. We also analyzed 129 patients aged over 75, of which 109 (84.4%) had absolute indication for oral anticoagulant therapy. Only 34 (31.2%) patients aged over 75 had been receiving vitamin K antagonist therapy and 6 (17.6%) had the International Normalized Ratio values within the proposed therapeutic interval. We found a significantly higher rate of anticoagulant therapy introduction in patients under 75 years (p=0.03), but there were no significant differences in the adequacy of anticoagulant therapy (p=0.89) between these two populations. Our results showed clear inadequacies of vitamin K antagonist treatment with a growing need for a wider use of novel oral anticoagulants.