Patients with mechanical heart valve prostheses require lifelong anticoagulation to reduce the risks of valve thrombosis and thromboembolism. These risks are greatest in the first three months after surgery and are exacerbated by inadequate anticoagulation. Although it is recognised that anticoagulant control is worse in the first few months after starting treatment, the relationship of this to warfarin dosing and the frequency of monitoring is unclear. We have therefore assessed the precision of anticoagulant control in the first three months after mechanical heart valve replacement and taken and analysis of influencing factors.
Eighty-five consecutive patients who underwent isolated mechanical heart valve replacement between April 1997 and March 1998, were identified retrospectively from hospital records. Of these were excluded patients in taking a medicine appearing drug interactions or decreasing the liver function. The clinical data included patients demographics, warfain dosages and INR changes for the first six months after surgery, weight changes, warfain maintenance dosages by age, sex, valve type.
Warfarin mean daily doses were 3.79±1.9, 3.60±1.67, 4.04±1.5, 4.36±1.6, 4.62±1.42, 4.98±1.6㎎ at postdischarge, 2 weeks, 1, 2, 3 and 6 months, respectively. Theses increased significantly. Patients gained weight but it was not significantly between weight and warfain dosages changes. Theses were not influenced by the valve type, age but significantly increased 19.3±0.31% male, 80±0.84% female, respectively. These results suggested that there is a sex difference in the anticoagulation effects of warfarin.
The anticoagulant response to warfarin is changed for the first three month after mechanical valve replacement. Therefore it is nescessary to control strictly for this periods.
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