An Investigator-initiated Linked Study to OCEANIC-AF

Inclusion Criteria: 1. Patients aged 18 years or over 2. Patients enrolled in OCEANIC-AF study 3. Free from the exclusion criteria below 4. The patient is willing and able to understand the Patient Information Sheet and provide written informed consent 5. The patient agrees to comply with the drawing of blood samples for the assessments. Exclusion Criteria: 1. Inability to provide valid informed consent 2. Patients aged \< 18 years of age 3. Patients with significant neurological, hepatic, renal, endocrine, gastrointestinal, pulmonary, haemorrhagic, metabolic or other disease likely to confound the study requirements or analyses 4. Patients with a history of substance abuse or signs or clinical features of active substance abuse or psychiatric disease 5. Alcohol consumption above 21 units per week 6. Any illness deemed significant by the investigator during the four (4) weeks preceding the screening period of the study 7. Any major bleeding diathesis or blood dyscrasia (platelets \<70 x 109/l, Hb \<80 g/dl, INR \>1.4, APTT \>x 2 UNL, leucocyte count \<3.5 x 109/l, neutrophil count \<1 x 109/l)