Prognosis in patients achieving ≥10 METS on exercise stress testing: was SPECT imaging useful?

Area of Science:

• Cardiology
• Nuclear Cardiology
• Diagnostic Imaging

Background:

• The prognostic value of myocardial perfusion imaging (MPI) compared to exercise ECG stress testing alone is not well-defined for patients reaching a workload of ≥10 METS.
• This study addresses intermediate pretest risk or known coronary artery disease (CAD) patients achieving ≥10 METS.

Purpose of the Study:

• To assess mortality and nonfatal cardiac events in patients with intermediate risk or known CAD who achieve ≥10 METS on exercise stress testing.
• To determine if peak exercise heart rate influences outcomes in this cohort.

Main Methods:

• Prospective study of 509 patients reaching ≥10 METS, comparing outcomes based on achieving ≥85% of age-predicted heart rate.
• Quantitative gated (99m)Tc-SPECT MPI was utilized to assess perfusion and function.
• Follow-up collected data on all-cause and cardiac mortality, non-fatal myocardial infarction (MI), and late revascularization.

Main Results:

• Of 509 patients, 463 had mortality follow-up. Cardiac events were rare, with only one cardiac death (0.1%/year).
• The prevalence of significant left-ventricular (LV) ischemia (≥10%) on MPI was very low (0.6%), irrespective of heart rate achieved.
• No cardiac events correlated with exercise ST depression or significant LV ischemia on MPI.

Conclusions:

• Patients with intermediate risk or known CAD achieving ≥10 METS have an excellent prognosis with very low rates of ischemia and cardiac events.
• Cardiac events in this cohort did not correlate with MPI findings, suggesting limited added value of MPI beyond exercise ECG stress testing.
• Attaining ≥10 METS during exercise stress indicates a favorable short-to-intermediate term prognosis, irrespective of peak heart rate.