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It has been recognized for many years that patients who achieve a high workload on exercise stress testing have an excellent prognosis, particularly in the absence of ischemic ST segment depression. Outpatients with a low-risk Duke Treadmill Score (based on exercise duration, magnitude of ST deflection and an angina index) had an observed annual mortality rate of only 0.25%. Exercise capacity has been shown to be a better predictor of all-cause mortality than maximum exercise heart rate. Myers et al reported that patients achieving a workload of C10 metabolic equivalents (METs), even in the presence of cardiovascular disease, had a relatively low risk of death during follow-up. For every 1-MET increment in peak treadmill workload, there was an associated 12% improvement in survival. These investigators found that, in both healthy subjects and those with cardiovascular disease, the peak exercise capacity was a stronger predictor of an increased risk of death than clinical variables or coronary artery disease (CAD) risk factors such as hypertension, smoking, and diabetes. It had greater prognostic value than peak exercise heart rate, ST depression, or exercise-induced arrhythmias. Morise et al found a 14% reduction in cardiac events among subjects\65 years of age, and an 18% reduction among subjects C65 years of age for each 1-MET increase in workload. After adjustment for age, the peak METs achieved was the strongest predictor of subsequent mortality. In another study, among patients with a positive exercise ECG, who achieved C10 METs, 93% had a negative exercise echocardiogram and less than 1% mortality after 7.2 years of follow-up. More recently, Bourque et al from the University of Virginia reported that in more than 470 consecutive patients referred for exercise SPECT myocardial perfusion imaging (MPI), who achieved C85% of maximum predicted heart rate (MPHR) and C10 METs, the prevalence of significant ischemia defined as comprising 10% or more of the left ventricle (LV), was only 0.4%. In fact, no patient who achieved C10 METs without ischemic ST depression had significant ischemia on MPI. The prevalence of 5-9% LV ischemia in such patients was also very low at 0.7%. This population had an intermediate-to-high pretest likelihood of CAD, with 20% having known CAD and 70% with chest pain as the indication for testing. Ischemia involving C10% of the LV was also low (2.4%) in the 82 patients who achieved C10 METs, but \85% of MPHR. Bourque et al then published the subsequent cardiac mortality and nonfatal cardiac event rates in this patient cohort achieving C10 METs. They reported a remarkably low annual cardiac mortality of 0.1% and a combined annual cardiac death or nonfatal myocardial infarction rate of 0.4%. None of the event patients had either [5% or [10% LV ischemia, and none was in the subsets which achieved\85% of MPHR or who had ST depression. Therefore, even if perfusion imaging was performed, it would not have identified the patients who subsequently had events. Interestingly, the annual cardiac death or nonfatal infarction rate was lower in patients who achieved C10 METs than observed in patients with normal stress perfusion scans regardless of workload achieved. These studies by Bourque et al, together with prior published reports relating the excellent prognosis in patients achieving high exercise workloads, bring into question the added prognostic value, and cost-effectiveness of MPI or stress echo in patients achieving C10 METs and no ischemic ST depression, regardless of the exercise heart rate and whether they have a history of prior CAD. From the Cardiovascular Division, Department of Medicine, University of Virginia Health System, Charlottesville, VA; and Mid America Heart and Vascular Institute, Saint Luke’s Health System, Kansas City, MO Reprint requests: George A. Beller, MD, Cardiovascular Division, Department of Medicine, University of Virginia Health System, Box 800158, Charlottesville, VA 22908; gbeller@virginia.edu. J Nucl Cardiol 2013;20:711–4. 1071-3581/$34.00 Copyright 2013 American Society of Nuclear Cardiology. doi:10.1007/s12350-013-9742-y

Provisional use of myocardial perfusion imaging in patients undergoing exercise stress testing: A worthy concept fraught with challenges