Implementation of a Myocardial Perfusion Imaging Risk Algorithm to Inform Appropriate Downstream Invasive Testing and Treatment

Background: To risk stratify patients undergoing single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) in accordance with appropriate use criteria for referral to coronary angiography, we developed a risk classification algorithm incorporating appropriate use criteria–defined risk features. We evaluated the association between this algorithm with downstream angiography, revascularization, and all-cause mortality. Methods: We studied consecutive patients who underwent SPECT-MPI from January 1, 2015, to December 31, 2017, and assigned a scan risk of low, intermediate, high, or indeterminate. With this stratification, we assessed referral for angiography and revascularization within 3 months of SPECT-MPI and intermediate-term mortality. Results: Among 12 799 patients, the mean age was 66 years, and a majority were men (56.8%). Most patients were low risk (83.6%) followed by intermediate (9.9%) and high risk (5.2%). Compared with low-risk patients, intermediate- and high-risk patients were more frequently referred for angiography (14.8% and 13.6% versus 2.0%; P <0.001) and revascularization (7.7% and 6.8% versus 0.7%; P <0.001). In 1008 propensity-matched patients, scan risk was independently associated with angiography after adjustment for ischemia, scar, or stress ejection fraction. At a mean follow-up of 2.3 years, mortality was higher with increased scan risk (high, 10.4%; intermediate, 7.1%; low, 4.1%; P <0.001). Compared with low scan risk, intermediate (hazard ratio, 1.37 [95% CI, 1.09–1.72]; P =0.008) and high scan risk (hazard ratio, 1.98 [95% CI, 1.53–2.56]; P <0.001) were associated with mortality in multivariable analysis. Similar findings were observed for those undergoing pharmacological and exercise SPECT-MPI with comparatively worse prognosis among pharmacological patients. Conclusions: This appropriate use criteria–derived risk classification algorithm for SPECT-MPI guided referral for coronary angiography and revascularization and was significantly associated with mortality. This algorithm may serve as an important tool to reaffirm appropriate use criteria and direct management of patients with stable ischemic heart disease undergoing stress testing.