Increased Sensitivity to Warfarin After Heart Valve Replacement

Abstract

Immediately after heart valve replacement, patients are more sensitive to warfarin and should receive a lower warfarin dose during the initial phase of oral anticoagulation treatment. This enhanced sensitivity decreases with time. Patients require frequent monitoring and are likely to need an increase in the warfarin dose to avoid insufficient anticoagulation during the early follow-up period.

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

“…For Meijer et al, the dose requirement of warfarin after 3 months of therapy was 26% higher compared to first week of therapy (Meijer et al, 2009 Results showed that warfarin requirements were in increasing trend during the first three months after heart valve replacement (both AVR and MVR) but this pattern was absent in patients with AF. The trend was consistent with previous studies (Meijer et al, 2009;Rahman et al, 2006). Several factors might contribute to the increasing trend of mean warfarin dose among patients with AVR and MVR.…”

“…Besides, diet which was different between Asian and Western populations might also contributed to the difference in warfarin dose needed (Jonas and McLeod, 2009) The mean warfarin dose in AVR and MVR patients after 3 months of therapy was 38.3% and 18.1% higher than first week of therapy. The result was consistent with study done by Mesbah Rahman et al and Meijer et al In result reported by Mesbah Rahman et al, the dose requirement of warfarin after 3 months of therapy was 43% higher compared to first week of therapy (Rahman et al, 2006). For Meijer et al, the dose requirement of warfarin after 3 months of therapy was 26% higher compared to first week of therapy (Meijer et al, 2009 Results showed that warfarin requirements were in increasing trend during the first three months after heart valve replacement (both AVR and MVR) but this pattern was absent in patients with AF.…”

“…Similarly, the mean warfarin dose in the study also lower as compared to results from Mesbah Rahman et al where they reported the mean dose (SD) of warfarin increased from 3.55 mg (1.94) to 5.09 mg (2.03) at the first week and twelfth week respectively after heart valve replacement (Rahman et al, 2006). The trend of lower mean warfarin dose in the study compared to the one reported in Western countries (Meijer et al, 2009;Rahman et al, 2006) was consistent with studies done by others Asian countries which showed Asian populations generally need lower dose of warfarin to achieved INR target (Jonas and McLeod, 2009;Mori et al, 2002;Sun et al, 2003;Yang et al, 2010;Zhou et al, 2005). This (Jonas and McLeod, 2009)) frequencies of Asian and Caucasian patients were different (Yang et al, 2010).…”

“…Several factors might contribute to the increasing trend of mean warfarin dose among patients with AVR and MVR. Factors known to affect the warfarin sensitivity including recovery from hypoalbuminemia after surgery (Ageno and Turpie, 1999;Rahman et al, 2006), improvement in hepatic congestion and cardiac output (Rahman et al, 2006), increase in dietary intake of vitamin K and decreasing adherence to therapy (Meijer et al, 2009).…”

“…Lowest adequate intensity of anticoagulation is important to minimize the risk of bleeding (Fuster et al, 2001). The sensitivity to warfarin decrease after the initial period and the progressive decrease in warfarin sensitivity over several months often cause difficulty to reach and maintain a stable INR within therapeutic range (Meijer et al, 2009;Rahman et al, 2006). This study looked into the difference in warfarin doses after the initiation of warfarin therapy among patients with aortic valve replacement (AVR), mitral valve replacement (MVR) or atrial fibrillation (AF) and also between these three groups.…”