The aim of this study is to investigate the clinical significance of high INR (International Normalized Ratio) values (>9) in VKA (vitamin K antagonist) treated patients with atrial fibrillation. The clinical characteristics of these patients will be studied as well as the clinical presentation. Factors influencing on high INR values will be recorded and the aim is to seek out patients who have elevated risk of bleeding complications.

This is a retrospective study setting. Source data will be collected by reviewing medical records and through computer searches. The basic study population will be identified from laboratory INR test results taken between 2003-2015.

Identifying patients with INR values over 9 will be selected for further analysis, concerning the clinical presentation, patient characteristics, 90 day survival and adverse event rates. The focus is in identifying patient characteristics and factors influencing the risk of high INR value. Also we will analyse the effects of medically reversing the high INR values on stroke and other adverse event rates. The results will be collected manually using an electronic case report form, and analysed statistically using SPSS/SAS statistics tool.

Inclusion Criteria:

• VKA treatment, age > 18, INR >9,

Exclusion Criteria:

• age < 18

Patients treated with VKA for atrial fibrillation in the Southwest Finland hospital district area with INR value over 9.