Original Research
Sunday, October 13, 2024
12:45 PM–02:15 PM
Abstract
Introduction: Warfarin is the only guideline recommended anticoagulant indicated for mechanical valve replacement. There is an exaggerated response to warfarin in the early post-operative setting which leads to difficulty managing warfarin dosing.
Research Question or Hypothesis: The purpose of this study is to assess the relationship between warfarin initiation dose and warfarin interruption after mechanical valve replacement at Virginia Commonwealth University Health System (VCUHS).
Study Design: Single-center, retrospective chart review for quality improvement of VCUHS current guidance on warfarin initiation
Methods: This study included adult patients started on warfarin after mechanical heart valve at VCUHS from January 1, 2015 to June 30, 2023. Patients were divided into two groups; conservative initial warfarin dose <2.5 mg (n=92) and standard initial dose >2.5 mg (n=91). The primary composite outcome was the incidence of warfarin interruption attributed to supratherapeutic INR, rapid-rise INR, or bleeding. Other assessments included time to therapeutic range, hospital length of stay, and discharge warfarin dose. An independent t-test was used for analysis of continuous data and chi-squared or Fisher’s Exact for categorical data.
Results: There was no statistical difference in the composite outcome between groups. Warfarin interruption secondary to a rapid-rise INR occurred significantly more in the standard group (n=17) vs. conservative group (n=28), p=0.05. Overall, more patients in the standard group experienced supratherapeutic and rapid-rise INRs. Patients who received a conservative dose were more likely to have a longer time to therapeutic range but no difference in hospital length of stay. The average dose at discharge was 4 mg in both groups. In a subgroup analysis of the standard group, patients with cardiopulmonary bypass (CPB) =150 minutes were more like to meet the primary endpoint compared to those with CPB <150 minutes.
Conclusion: We recommend a standard initial warfarin dose of 4 mg and a conservative initial dose in patients with prolonged CPB (=150 minutes) at VCUHS.
Presenting Author
Leah Baker PharmDVirginia Commonwealth University Health System
Authors
Cassandra Baker PharmD
Virginia Commonwealth University Health System
Kenneth Potter MD
Virginia Commonwealth University Health System