• Kai-Hang Yiu, Chung-Wah Siu, Man-Hong Jim, Hung-Fat Tse, Katherine Fan, Mo-Chee Chau, and Wing Hing Chow.
• Cardiology Division, Department of Medicine, Queen Mary Hospital, Hong Kong, China.
• Am. J. Cardiol. 2006 Feb 1; 97 (3): 409-11.

AbstractPatients on warfarin for mechanical heart valves are at increased risk for thromboembolic events and intracranial hemmorhage. In current guidelines, a low dose of vitamin K is the recommended treatment for moderate over-anticoagulation based on studies in which only minority patients participating had mechanical heart valves. We performed a randomized controlled trial to compare the efficacy and safety profile of low-dose intravenous vitamin K and fresh frozen plasma (FFP) for patients with mechanical heart valves and mild to moderate over-anticoagulation (international normalized ratio [INR] 4 to 7). In a 24-month period, we randomized 102 patients to (1) vitamin K or (2) FFP. The baseline INR at presentation between the vitamin K group and the FFP group was 4.61 +/- 0.007 vs 4.78 +/- 0.07 (p = 0.11). Six hours after treatment, patients in the FFP group had a significantly lower mean INR compared with the vitamin K group (2.75 +/- 0.06 vs 3.44 +/- 0.10, p = 0.01). No patient in both groups had over-correction (INR < 2). One week later, there was no significant difference in mean INR between both groups (2.7 +/- 0.11 vs 2.56 +/- 0.12, p = 0.41). Fifty-eight percent of patients in the FFP group and 51% in the vitamin K group had an INR within the target range. There were no adverse reactions or outcomes in both groups. In conclusion, intravenous low-dose vitamin K is a safe alternative to FFP infusion for warfarin overdose in patients with mechanical heart valves.

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