Factors Affecting Medication Adherence in Patients with Mechanical Heart Valves Taking Warfarin: The Role of Knowledge on Warfarin, Medication Belief, Depression, and Self-Efficacy.

Non-adherence is highlighted as one of the main contributors to the occurrence of adverse events and negative clinical outcomes in patients treated with warfarin. The aim was to examine knowledge on warfarin, medication belief, depression, and self-efficacy as factors influencing medication adherence for anticoagulation control. This was a cross-sectional study. The participants in this study were patients who visited an outpatient clinic of cardiovascular surgery to administer anticoagulants after mechanical valve replacement surgery at a tertiary hospital in Seoul. Responses of 154 participants on questionnaires were analyzed from 10 September to 26 December 2020. Multiple regression analyses were performed to assess the factors influencing medication adherence among the patients with anticoagulation control. Factors influencing medication adherence were consuming warfarin for 3 to 5 years, awareness of target prothrombin time international normalized ratio, knowledge of warfarin, and depression. Medication beliefs and self-efficacy had no significant influence on medication adherence. The most important factors associated with medication adherence in patients with mechanical heart valves were knowledge about warfarin and depression. In the control of oral anticoagulants that require continuous management, education and providing accurate guidance is more important than personal preferences. Clinical nurses should facilitate educational programs tailored to the characteristics of the patient, including their purpose and method of taking warfarin, specific diets, their knowledge on warfarin's interaction with other drugs, symptoms of adverse events, and self-management. In addition, healthcare providers should check whether warfarin therapy is being controlled by evaluating medication adherence and depression levels among patients.