Warfarin is a medication typically referred to as a blood thinner and is used to prevent the formation of blood clots, and hence prevent life-threatening events such as strokes and clots on the lungs (known as pulmonary emboli). This therapy is only safe and effective if the degree of blood thinning is kept within a narrow window - if the blood is "too thick" clots may form but if the blood is "too thin" the risk of bleeding increases. Complicating the control of warfarin is that different people require different amounts of it to have an appropriate degree of blood thinning, and once this amount is determined for a patient, it may be changed by factors that are encountered on a daily basis (i.e., diet, acute and chronic diseases, alcohol, medications, etc.). As such, regular monitoring is necessary to confer the benefits of this medication. Our Anticoagulation Management Service (AMS) has demonstrated really good control of blood thinning therapy by working with patients to inform them of the rationale for this medicine, the factors having the ability to impact its control, and encouraging the patient to be involved in their care (via provision of tools to document test results, one-on-one education and access to our program at any time with questions, etc.) Currently, our AMS has to limit the volume of patients seen due to resource limitations. As such, it is imperative that we investigate alternate strategies to manage these patients. Paramount, however, is that any long-term strategy must not confer inferior control of warfarin. The purpose of this study is to determine if the impact of AMS Care is sustained following the transfer of anticoagulation management to the family doctor. Operationally, the results of this study will guide future management of patients. If control of warfarin therapy declines with family doctor management, alternate strategies, such as patient self-management, will need to be investigated in a larger scale trial.

Inclusion Criteria:

• current patient of the Anticoagulation Management Service
• anticipated need for long term anticoagulation
• have a regular primary care physician

Exclusion Criteria:

• previous failure of warfarin therapy (a bleed or clot despite therapeutic anticoagulation
• have a planned procedure (surgery) mandating discontinuation of warfarin
• are taking warfarin for a mechanical valve indication