INR Control of Patients with Mechanical Heart Valve on Long-Term Warfarin Therapy

Warfarin is an anticoagulant indicated for patients who had undergone mechanical heart valve(s) replacement (MHVR). In these patients, time in therapeutic range (TTR) is important in predicting the bleeding and thrombotic risks.

This study aimed to describe the anticoagulation control of warfarin using TTR in patients with MHVR in a tertiary health care referral Center.

Data were collected retrospectively by reviewing clinical notes of outpatients who attended international normalized ratio (INR) clinics in November 2015. Patients who had MHVR and who took warfarin were included. The data collected were demographics, relevant laboratory investigations, and patients' prior medical history. TTR was calculated using Rosendaal and traditional methods.

A total of 103 patients with MHVR were recruited. The mean age was 51.72 ± 13.97 years and 46.6% were male. A total of 54.4% had mitral valve replacement (MVR), whereas 26.2% had aortic valve replacement (AVR). The mean TTR calculated using the Rosendaal method was 57.1%. There was no significant difference among patients with AVR, MVR, and both valves (AMVR) in terms of TTR (AVR vs. MVR vs. AMVR, 62.94 ± 23.08, 54.12 ± 21.62, 57.63 ± 17.47; p = 0.213). The average dose of warfarin for all groups was approximately 3 mg/day. Moreover, MVR, AVR, and AMVR patients who had TTR (Rosendaal method) ≤60% were 58.9%, 37.0%, and 45.0%, respectively. Only 4.8% had minor bleeding, whereas none had stroke in the period of TTR determination.

Despite a majority of patients having <60% TTR, there were low incidences of bleeding and stroke events in this center. There were no factors found to be associated with INR control in this study.