Plasma concentrations of factor Xa inhibitors and stroke risk in patients with atrial fibrillation

Aim . To determine plasma concentrations of direct oral anticoagulants (DOACs) in patients with ischemic stroke (IS) associated with atrial fibrillation (AF) and to compare them with DOAC levels in patients with AF but without IS receiving similar therapy. Material and methods. A prospective cohort study was conducted at the Vascular Center of S.P. Botkin Moscow City Clinical Hospital from April 2022 to April 2023. The study included 82 patients with cardioembolic stroke on the background of AF (main group) and 130 AF patients without stroke or transient ischemic attack (TIA) (control group). All patients had been receiving DOACs (apixaban or rivaroxaban) for at least 3 months. Diagnostic workup included brain computed tomography, сarotid ultrasound, laboratory tests, and stroke severity assessment by NIH Stroke Scale (NIHSS). Plasma DOAC concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The lower limit of quantification (LLOQ) was 5 ng/mL. Results . Patients in the main group had significantly more frequent subtherapeutic DOAC concentrations below the LLOQ compared to the control group (52.4% vs. 1.5%, p