The Impact of Appropriate Use on the Prognostic Value of SPECT Myocardial Perfusion Imaging

Background —Appropriate use criteria (AUC) have been developed to aid in the optimal use of SPECT-myocardial perfusion imaging (MPI), a technique that is a mainstay of risk-assessment for ischemic heart disease. The impact of appropriate use on the prognostic value of SPECT-MPI is unknown. Methods and Results —A prospective cohort-study of 1511 consecutive patients undergoing outpatient, community-based SPECT-MPI was conducted. Subjects were stratified based on the 2009 AUC for SPECT-MPI into appropriate or uncertain appropriateness group and inappropriate group. Patients were prospectively followed for 27±10 months for major adverse cardiac events (MACE) of death, death or myocardial infarction (MI), and cardiac death or MI. In the entire cohort, the 167 (11%) subjects with abnormal scan expectedly experienced significantly higher rates of MACE and coronary revascularization than those with normal MPI. Among the 823 (54.5%) subjects whose MPIs were classified as appropriate [779 (51.6%)] or uncertain [44(2.9%)], abnormal scan predicted a multi-fold increase in the rates of death [9.2% vs. 2.6%;HR=3.1; P =0.004], death or MI [11.8% vs. 3.3%;HR=3.3; P =0.001], cardiac death or MI [6.7% vs. 1.7%;HR=3.7; P =0.006], and revascularization [24.7% vs. 2.7%;HR=11.4; P <0.001]. However, among the 688 (45.5%) subjects with MPI classified as inappropriate, abnormal MPI failed to predict MACE, although was associated with a high revascularization rate. Furthermore, appropriate MPI use provided an incremental prognostic value beyond myocardial perfusion and ejection fraction data. Conclusions —When performed for appropriate indications, SPECT-MPI continues to demonstrate high prognostic value. However, inappropriate use lacks effectiveness for risk-stratification, further emphasizing the need for optimal patient selection for cardiac testing.