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2015 HSR&D/QUERI National Conference Abstract

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1048 — Clinical Utility of Inappropriate Nuclear Myocardial Perfusion Imaging in a Veteran Population

Winchester DE, Malcom Randall VAMC; Chauffe RC, University of Florida; Meral R, University of Florida; Shaw LJ, Emory University; Beyth RJ, Malcom Randall VAMC;

Objectives:
Appropriate Use Criteria (AUC) for nuclear myocardial perfusion imaging (MPI) were developed to guide clinicians towards indications that will benefit patients. The association between inappropriate MPI and cardiovascular outcomes is not well described. We sought to determine the clinical utility of inappropriate MPI.

Methods:
We conducted a retrospective single center investigation of MPI performed our Veterans Affairs medical center. MPI were categorized based on 2009 AUC, uncertain and unclassifiable indications were excluded. Patient data were extracted from the encounter where MPI was ordered. Major adverse cardiac events (MACE: death, infarction, hospitalization, revascularization, or catheterization) were assessed at one year. Multivariate regression including odds ratios (OR) with 95% confidence intervals (CI), was performed to correlate patient characteristics with MACE.

Results:
The study population included 524 subjects, predominantly male (96.6%) and obese (68.1%) with a significant burden of coronary artery disease (CAD, 61.1%) and CAD risk factors (diabetes 42.0%, hypertension 76.0%, hyperlipidemia 76.0%, and tobacco use 25.6%). Of 57 inappropriate MPI, only 4 were abnormal. The prevalence of abnormal MPI was lower for inappropriate tests as compared to appropriate tests (7.3% versus 28.8%, OR 0.20, 95% CI 0.06-0.59, p < 0.0001). Of the MPI that were both inappropriate and abnormal, none detected occult ischemia. MACE occurred with fewer inappropriate MPI as compared to appropriate MPI (5.3% versus 24.4%, OR 0.17, 95% CI 0.04-0.59, p < 0.0001). In multivariate regression, CAD (OR 2.58, 95% CI 1.53-4.35, p < 0.0001), summed stress score ? 5 (OR 2.32, 95% CI 1.05-5.08, p < 0.036), and summed difference score ? 5 (OR 6.52, 95% CI 2.63-19.17, p < 0.0001) were associated with MACE.

Implications:
Inappropriate MPI tests were less likely to be abnormal compared to appropriate MPI. Of all inappropriate MPI tests performed, none detected occult ischemia. MACE occurred less frequently in subjects with inappropriate MPI. In this population with high CAD prevalence, inappropriate MPI testing appears to offer minimal clinical utility.

Impacts:
Clinical validation of AUC justifies their use in prospectively directing clinicians away from inappropriate indications. Interventions based on this strategy could reduce inappropriate testing which may reduce patient radiation exposure, reduce costs, and increase access to care.