Abstract 320: Low Prevalence of Ischemia and Excellent Prognosis in an Intermediate-Risk Cohort Achieving ≥10 METS on Exercise Myocardial Perfusion Imaging: Was SPECT Imaging Necessary?
Introduction: Increasing yearly volumes of stress myocardial perfusion imaging (MPI) are a cost burden on the healthcare system. The benefit of MPI over exercise electrocardiography is unclear in individuals attaining a high cardiac workload of ≥10 METS. The purpose of this study was to determine the 1-year outcomes in this cohort at intermediate risk for CAD or with known CAD (11.1%) achieving ≥10 METS regardless of peak exercise heart rate.
Methods: Ischemia and LV function were obtained by quantitative gated 99mTc-SPECT MPI in 554 consecutive patients reaching ≥10 METS of exercise workload. One-year rates of all-cause mortality, cardiovascular (CV) death, and non-fatal myocardial infarction (MI) were prospectively-collected through mailed questionnaires, patient and physician telephone contact, patient records, and the social security death index.
Results: All-cause mortality and CV death were ascertained in 504 of 554 patients (91.0%) and non-fatal MI in 459 subjects (82.9%). No difference was observed in cardiac risk factors, ejection fraction, or rates of significant ischemia (≥10% LV) based on follow-up ascertainment. The follow-up cohort had a mean age of 53.1±11.9 (SD); 70.6% were male, and 15.0% and 20.4% had prior MI and revascularization, respectively. Ischemic ST-depression occurred in 9.1%. The rate of ≥10% LV ischemia by MPI was very low at 0.7% (4/504). Only 34 (6.1%) had any ischemia. Six (1.1%) had an LVEF <40%. Death occurred in 8/504 patients (1.6%) who attained ≥10 METS. There were no CV deaths, and none had ≥10% LV ischemia; 3/459 patients (0.7 %) had a nonfatal MI in the 1st year post testing, 1 of whom had ≥10% LV ischemia. Only 8 of the 459 patients had cardiac catheterization, 2 with revascularization, between 4 and 52 weeks after stress MPI.
Conclusions: Thus, patients at intermediate risk for CAD or known CAD achieving ≥10 METS had a very low prevalence of ≥10% LV ischemia, and one-year rates of all-cause mortality and nonfatal MI were very low. No CV deaths occurred. The events did not correlate with SPECT abnormalities. These results suggest that patients who attain ≥10 METS during exercise stress have an excellent short-term prognosis. The added value of stress MPI to standard exercise ECG testing in this population is questionable.