Evaluation and Optimization of INR Goals in Patients With Mechanical Aortic Valves in a Pharmacist-Run Clinic: An Anticoagulation Stewardship Initiative

Abstract

Background:

Patients with a mechanical aortic valve replacement (AVR) require lifelong anticoagulation with warfarin. International normalized ratio (INR) goals for mechanical AVRs can change throughout treatment as risk factors change. Appropriate INR goal selection is crucial as goals that stray from evidence-based recommendations can lead to increased risk of bleeding, thrombosis or unnecessary monitoring.

Objective:

The purpose of this study was to evaluate the appropriateness of INR goals in patients with mechanical AVRs and identify opportunities for pharmacist-led intervention.

Methods:

A cross-sectional quality improvement study was conducted at a safety net academic medical center’s outpatient anticoagulation clinic. This quality improvement project was not formally supervised by the Institutional Review Board per their policies. Adult patients with isolated mechanical AVR actively managed on warfarin were included. Pharmacists determined whether INR goals were justified by clinical context and American and European valvular heart disease guidelines. When goals lacked clear justification, pharmacists contacted referring providers to recommend INR goal adjustment.

Results:

Of 100 identified patients, 81 met eligibility criteria including 24 (29.6%) with On-X valves and 57 (70.4%) with alternative mechanical AVRs. Nearly one-third of patients (23, 29.3%) had INR goals inconsistent with current guidelines. Pharmacist-led outreach resulted in 20 accepted recommendations (87.0%), representing 24.7% of the study population. On-X valve recommendations primarily involved reducing INR targets to 1.5 to 2.0 for patients at least 3 months postsurgery without other risk factors that would constitute a higher INR goal. The most common alternative mechanical valve interventions included increasing INR goals to 2.5 to 3.5 in those with thromboembolic risk factors and decreasing INR goals to 2.0 to 3.0 due to absence of thromboembolic risk factors.

Conclusion and Relevance:

This stewardship initiative highlights the need for periodic INR goal review, as risk factors in patients with mechanical AVRs can change over time.