JOURNAL OF NUCLEAR CARDIOLOGY NEWS UPDATE The PROMISE of Nuclear Cardiology

David Wolinsky MD, FACC, FASNC. President ASNC As nuclear cardiologists, we face challenges on a daily basis to prove the value of our field. What makes our task more difficult is that the definition of value has become more complex and our abilities to successfully demonstrate it on both large and small scales is becoming increasingly more challenging. In a classic paper in 1991,Fryback and Thornbury defined a six stage hierarchical model of efficacy as applied to cardiac imaging.1 The first two levels – technical reproducibility and diagnostic accuracy -were successfully achieved during nuclear cardiology’s infancy. These successes allowed the field to grow and flourish as clinicians began to routinely incorporate the results of myocardial perfusion imaging (MPI) into their diagnostic thinking (level 3). Despite the successes diagnostic efficacy was defined by the exactness of anatomic correlation and not truly by defining treatment algorithms. MPI was touted as a noninvasive alternative to coronary angiography. A significant watermark in the field occurred in 2003 when Hachamovitch showed in a large observational study

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that the results of MPI not only predicted anatomic findings but that the severity of abnormalcy correlated with outcome based on treatment. Those patients with less than 12% ischemic myocardium had a more favorable outcome when managed with medical therapy whereas patients with greater than 12% ischemia appeared to do better with a revascularization strategy.2 Thus the fourth level of the Fryback model- therapeutic efficacy-was achieved. For the first time there was data to suggest ischemia-guided therapy seemed to be an appropriate management strategy. Stress MPI became a mainstay for the management of patients with suspected coronary disease. Many opposing factors however evolved to modify the role of nuclear cardiology. Utilization of MPI peaked in the mid 2000’s. Efforts were made to curb growth were it was felt to be excessive. The first ACC/ACC/AHA Appropriate Use Criterion document was released in 2005. Payers and their representatives radiology benefits managers (RBMs) began to restrict utilization. Simultaneously other functional tests such as stress echocardiography grew as a competing technique. Stress echo offered lower cost and lower radiation exposure but had a far less robust body of supporting research. Still ischemia- guided therapy appeared to be an effective algorithm for patient management. The fifth level of Fryback’s model is patient outcome efficacy. As a field we were challenged not only to define risk with imaging but prove that patient outcomes were improved with MPI. That is, imaging results defined a particular therapy that was associated with improved outcomes compared to those patients not undergoing MPI. This should be demonstrated with randomized trials. Downstream adverse effects and subsequent procedures would be avoided. All of this should be achieved based in a cost-saving or cost- effective model. Despite changes that occurred in the health care delivery paradigm, several studies have demonstrated that nuclear cardiology can satisfy the fifth level of imaging efficacy. The COURAGE nuclear substudy showed that in patients undergoing serial MPI, patients who achieved a greater than 5 per cent reduction in ischemia regardless of treatment modality -optimal medical therapy (OMT) versus OMTplus revascularization- had a more favorable prognosis.3 This was a small study that was hypothesis-generating; limited conclusions can be drawn that would further change

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management paradigms. We anxiously await the results of the ISCHEMIA which will test in a randomized prospective manner whether a routine invasive strategy is superior to OMT alone in patients with moderate to sever ischemia. In the last decade noninvasive anatomic assessment with coronary CTA has evolved as an alternative strategy to functional testing. The negative predictive value of a normal CCTA has been well demonstrated but defining its overall role in specific populations has been less well established. CCTA’s true value had yet to be defined when compared to physiologic or functional testing. Proponents of CCTA touted lower radiation doses, lower procedural cost, and identification of nonobstructive pathology of advantages over MPI. As described above the fifth level of the Fryback’s model is the most important reflection of the benefit of a test on individual patient outcomes. New healthcare models however are demanding value not on an individual patient basis but on a societal level. Level 6 defines cost-effectiveness on a societal level. Is the added cost of test and subsequent treatment justified to be applied to a given patient or patient population? Several recent studies have recently shown that nuclear cardiology stands out when compared to other modalities when using these benchmarks. The SPARC study was an observational registry comparing SPECT MPI, PET, and CTA. After multivariable adjustment CTA was associated with a 15% greater cost while showing no mortality benefit over SPECT.4 Prospective randomized studies however remain as the holy grail of outcomes research. Many questions remained unanswered when the two imaging approaches—anatomic vs. functional. Of foremost importance were patient outcomes. Other comparative measures included downstream testing, frequency of subsequent interventional procedures, and cost. This it was with great anticipation and anxiety that the field of nuclear cardiology awaited the presentation of the PROMISE study at the 2015 ACC annual meeting.

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PROMISE was an NIH-sponsored prospective study comparing anatomic versus functional diagnostic testing strategies in patients being evaluated for suspected symptomatic CAD. Though patients were randomized to CCTA versus stress testing, clinicians were allowed to select the stress test of their choice for patients in the functional arm. It should be noted that 67% of these patients were referred for stress MPI attesting to the clinical utility of nuclear cardiology in everyday practice. The primary outcome-combined endpoint of death, myocardial infarction, unstable angina, and major complications-showed no advantage to anatomic testing with CCTA.5 Additionally the functional testing arm was associated with less coronary angiography, less revascularization, and less coronary artery bypass procedures all while maintaining similar outcomes. Anatomic testing with CCTA remained more expensive throughout the study and radiation exposure in the nuclear arm was only minimally greater than in the CCTA arm. The future remains strong for nuclear cardiology. ASNC is committed to quality and value. We have expanded all of our educational initiatives. The Annual Scientific Session in Washington DC in September will focus not only on improving the day to day practice of nuclear cardiology but will seek to educate those for whom nuclear cardiology is important to patient care. We will have sessions geared towards referring clinicians and also towards other cardiovascular specialists who make management decisions based on test results. Our advocacy specialists will update and help prepare attendees to utilize mandatory decision support tools. The future of nuclear cardiology will also be emphasized with expansive sessions on the role of cardiac PET and the role of nuclear cardiology in disease management with sessions on sarcoidosis, amyloidosis, and cardio-oncology. Additionally our technologist sessions have been expanded. Don’t miss this opportunity. It will be well worth your while. We PROMISE.

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References 1. Fryback DG, Thornbury JR. The efficacy of diagnostic imaging. Med Decis Making. 1991;11:88–94. 2. Hachamovitch R, Hayes SW, Friedman JD, Cohen I, Berman DS. Comparison of the short-term survival benefit associated with revascularization compared with medical therapy in patients with no prior coronary artery disease undergoing stress myocardial perfusion single photon emissions computed tomography. Circulation. 2003;107:2900–6. 3. Shaw LJ, Berman DS, et al. Optimal medical therapy with or without percutaneous coronary intervention to reduce ischemic

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burden. Results from the Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) Trial Nuclear Substudy. Circulation. 2008;117:1283–91. 4. Hlatky MA, Shilane D, Hachamovitch R, DiCarli MF. Economic outcomes in the study of myocardial perfusion and coronary anatomy imaging roles in coronary artery disease. The SPARC Study. J AM Coll Cardiol. 2014;63:1002–8. 5. Douglas PS, Hoffmann U, Patel MR, et al. Outcomes of anatomical versus functional testing for coronary artery disease. NEJM. 2015;372:1292–300.

The PROMISE of Nuclear Cardiology.

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