The Initiation Phase of Warfarin Therapy: Differences of Dose among Patients with Aortic Valve Replacement, Mitral Valve Replacement and Atrial Fibrillation

Article history: Received on: 01/06/2016 Revised on: 18/08/2016 Accepted on: 05/09/2016 Available online: 29/11/2016 This study was conducted to evaluate the changes in warfarin doses among patients after heart valve surgery and atrial fibrillation. A total of 137 patients having AF, AVR and MVR whom initiate warfarin therapy in year 2008 till 2010 in Penang Hospital were selected as samples for this study. Data collected included patient’s age, race, gender, warfarin initiation date, warfarin indication, warfarin dose and INR value for 1 st till 12 th weeks of warfarin initiation. Heart valve replacement patients (AVR or MVR) showed increasing trend in warfarin doses during the initial phase of warfarin therapy. This trend was not observed in AF patients. The dose of warfarin was significantly different within first 12 weeks of warfarin initiation for AVR and MVR group (p<0.001) but there was no significant difference in AF group. The dose of warfarin was significantly different among AVR and AF patients for first 5 weeks of warfarin initiation. Monitoring should be frequent for patients with heart valve replacement during the initial 3 months period of warfarin therapy.