OBJECTIVES: The aim of this study is to analyze consequences of the poor anticoagulation control with VKA, in terms of thrombotic events, bleedings and mortality, in patients with non-valvular atrial fibrillation (NVAF). The use of healthcare resources and healthcare costs are also estimated.

METHODS: This observational and retrospective study was based on the electronic medical records of 1.8 million individuals included in the BIG-PAC^® database. The study considered patients with NVAF who started their treatment with vitamin K antagonists (VKA) (acenocoumarol or warfarin) between 01/01/2016 and 31/12/2018. Patients were classified as those with poor anticoagulation control (Rosendaal or direct methods) or adequate anticoagulation control. Patients were followed up two years. Demographic and clinical characteristics, treatments, incidence of cardiovascular events, mortality rates, use of healthcare resources and healthcare costs (Euros, 2021) were analyzed.

RESULTS: The study included 2,136 and 2,351 patients with poor and adequate anticoagulation control, respectively. Patients with poor anticoagulation control had a 25% increase in the risk of suffering cardiovascular events than patients with adequate control (HR = 1.75 [95% confidence interval, CI: 1.43 - 2.14; p<0.001]). Patients with adequate anticoagulation control had a lower incidence of cardiovascular events [47.3%] (major bleedings [46.2%], minor bleedings [29.6%), systemic thromboembolism [22.2%] and ischemic strokes [16.1%]), and lower mortality rates than those with poor control. Patients with adequate anticoagulation control also required fewer visits to primary care physicians, nurses, and specialists, in comparison to patients with poor control. From the perspective of the Spanish National Health System, it was estimated that having an adequate anticoagulation control saved €455 per patient, mainly due to the reduction of hospitalizations.

CONCLUSIONS: Having a poor anticoagulation control in NVAF patients on treatment with VKA was associated with a higher incidence of cardiovascular events, a higher consumption of healthcare resources and higher management costs.