LAUSR

About 6 months ago, I reviewed a manuscript, and subsequently wrote an editorial, pertaining to a retrospective study undertaken by Mayo Clinic investigators, reporting a marked decline in the annual volume of SPECT myocardial perfusion imaging (MPI) studies in patients with known CAD, from 1425 in 2003, to 552 in 2012. This report followed a prior publication from the same group in 2016, indicating that the volume of SPECT MPI in patients without known CAD had decreased from 2490 in 2003 to 1033, in 2012. In the more recent report, the authors further showed that the percentage of high-risk SPECT results also diminished over time, from 47.8% of all studies in years 1991-1995, to only 8.1% in years 2011-2012. This decrease in highrisk SPECT imaging results occurred, even though the prevalence of CAD risk factors, except for smoking, in the tested population increased over this time period. A similar observation was made by the Cedars Sinai group, which reported a progressive decrease in abnormal SPECT MPI studies from 40.9% in 1991 to 8.7% in 2009. The incidence of stress-induced ischemia fell from 29.6% to 5.0% of imaging studies, accompanied by a marked decrease in patients manifesting moderate-to-severe ischemia. Other studies in the literature confirm the Mayo Clinic observation of a decrease in volume of SPECT MPI in the past decade. Medicare data revealed that the radionuclide MPI rate per 100 Medicare beneficiaries rose from 63.4 in 2001, to a high of 88.0 in 2006, but then significantly declined each year thereafter, reaching a value of 10.8 in 2013. A Kaiser Permanente database study revealed a 51% decline in the annual rate of MPI procedures from 2006 to 2011. Other reports in the literature also confirm the diminution over time of abnormal test results. The average rate of abnormal stress tests in 4 multicenter studies in which functional stress testing was compared to coronary computed tomography angiography (CTA) was only 14.5%. The Prospective Multicenter Imaging Study for Evaluation of Chest Pain (PROMISE) trial showed that just 12.6% of patients in the functional testing arm had abnormal tests. The risk of death, nonfatal myocardial infarction, hospitalization for unstable angina, or major complications related to diagnostic testing or cardiovascular procedures after an abnormal functional test was only 3.0% at 25 months of follow-up. These data showed that the prognosis in the population tested was quite favorable, even after a positive test result. At the University of Virginia, a total of 3302 SPECT MPI studies, and 347 gated blood pool scan (MUGA) studies, were performed in 2006. By 2017, the number of SPECT MPI and MUGA procedures had decreased to 2021 and 103, respectively. However, this decrease in SPECT MPI was attenuated by the performance of 365 PET MPI studies in 2017. The possible explanations for the decrease in volume in SPECT MPI and fewer high-risk imaging findings are myriad, and were discussed in the editorial. Certainly, the emergence of Appropriate Use Criteria in 2005 had an impact on reducing referrals for SPECT MPI, particularly in asymptomatic patients, and those that had undergone uncomplicated revascularization procedures. Routine functional stress testing after an uncomplicated acute coronary syndrome, or 3-6 months George A. Beller, Editor Emeritus, Journal of Nuclear Cardiology