ORION is a retrospective, observational, one center study to evaluate the incidence of complications (both thromboembolic and bleedings) in a cohort of patients receiving Vitamin K antagonists (VKA) under a self-management program, since 2002 at the Hospital de la Santa Creu i Sant Pau in Barcelona (Spain)

Inclusion Criteria:

1. Adult patients (older than 18) under chronic VKA treatment, whom performed patient self-management for any indication of oral anticoagulation.
2. Signed informed consent

Exclusion Criteria:

1. Patients younger than 18 years old

Patients suffering from atrial fibrillation, or carrying a cardiac mechanical valve prostheses, or suffering any other cardiac disease with risk of arterial embolism or with a previous venous thromboembolic event with high risk of recurrence, and receiving chronic oral anticoagulation (OA) with any VKA drug, and whom have been trained in our Unit by specialized nurses on self-management of their OA by using a portable coagulometer to weekly test the International Normalized Ratio (INR)