Analysis of Factors Affecting Nontherapeutic INRs in Korean Outpatients with Mechanical Heart Valves / 대한흉부외과학회지

ABSTRACT

BACKGROUND: Following the implantation of heart valve prostheses, it is important to maintain therapeutic INR to reduce the risk of thromboembolism. The objectives of this study were to determine the causes of nontherapeutic INRs, and to identify the factors associated with nonadherences to warfarin therapy in Korean outpatients with prosthetic heart valves managed by a pharmacist-run anticoagulation service (ACS). MATERIAL AND METHOD: A retrospective chart review was completed for all patients enrolled in the ACS at Seoul National University Hospital from March, 1997 to September, 2000. The data on 868 patients (5,304 visits) who were at least 6 months post-valve replacement were included. All possible causes of nontherapeutic INRs were documented for each patient visit. The association of covariates to noncompliance was investigated by univariate analysis. RESULT: The reasons for nontherapeutic INRs were identified as follows inadequate dosage adjustment (21%), nonadherences to dosing regimen (13%), drug/herbal interactions (12%), changes in diet (7%), and indeterminate cause (42%). Younger age, shorter duration of ACS and longer duration of warfarin therapy were associated with nonadherence. CONCLUSION: In this study, nonadherence and interactions between diet and medications were found to be important factors influencing nontherapeutic INRs. Longer duration of enrollment in the ACS affected the adherence to warfarin therapy positively whereas younger age and longer duration of warfarin therapy affected negatively.