Abstract 13900: Very Low Cardiac Event Rate in Patients Achieving ≥10 METS Regardless of Peak Exercise Heart Rate With No Supplemental Value of SPECT Myocardial Perfusion Imaging
Background: Patients achieving high exercise workloads or high peak exercise heart rates are reported to have lower cardiac event rates than patients with poor exercise tolerance. We sought to prospectively determine if myocardial perfusion imaging (MPI) provided additional prognostic information over peak exercise METS achieved, even in patients who failed to attain ≥85% of maximum age-predicted heart rate (MAPHR).
Methods: A group of 463 consecutive patients with intermediate-to-high probability of coronary artery disease (CAD) referred for exercise MPI who attained ≥10 METS were divided into those achieving ≥85% MAPHR (Group 1, n=395) or <85% MAPHR (Group 2, n=68). All underwent symptom-limited, quantitative 99mTc-sestamibi MPI and were followed-up for cardiac death, nonfatal MI, and late revascularization (>2 months post-MPI).
Results: Group 2 patients had a higher prevalence of diabetes (23.5% vs. 10.9%, p=0.004), tobacco abuse (45.6% vs. 23.0%, p<0.001), known CAD (38.2% vs. 20.0%, p=0.001), and history of prior MI (29.4% vs. 11.9%, p<0.001). However, no difference was observed between Group 2 and Group 1 with respect to ≥10% LV SPECT ischemia (1.5% vs. 0.5%, p=0.360). The prevalence of any ischemia was greater in Group 2 (17.7% vs. 4.1%, p<0.001). Successful follow-up was accomplished for cardiovascular events in 415 patients (90%). Only 1 cardiac death (0.2%) and 3 nonfatal MIs (0.7%) occurred during a mean follow-up of 2.2 years. Only 1 patient had late revascularization. None of these event patients had had ≥5% LV ischemia on index MPI and none had ischemic ST depression. The 4 patients with cardiac death or nonfatal MI were in Group 1.
Conclusions: Thus, patients at intermediate risk for CAD or known CAD achieving ≥10 METS have a very low prevalence of ≥10% LV ischemia and very low rates of cardiac mortality, nonfatal MI, and late revascularization, irrespective of heart rate achieved. Cardiac events did not correlate with abnormalities on the index MPI study. These results suggest that patients who attain ≥10 METS during exercise stress have an excellent prognosis over an intermediate term of follow-up, regardless of peak exercise heart rate achieved. The added value of MPI to standard exercise ECG testing in this population is questionable.
- © 2010 by American Heart Association, Inc.