a high exercise workload of ≥ 10 mets predicts a low risk of significant ischemia and cardiac events in older adults

Patients who achieve ≥ 10 mets during exercise spect myocardial perfusion imaging (mpi) have very low rates of significant ischemia and major adverse cardiac events (mace). it is unknown how many older adults can achieve ≥ 10 mets, and if low risk extends to this subgroup. we examined the workload achieved, prevalence and predictors of ischemia, and mace (cardiac death, non-fatal mi, late revascularization) in a cohort of 382 patients ≥ 65 years of age who underwent exercise 99mtc spect mpi. the cohort was 64.4% male and 36.9% had known coronary artery disease (cad). all achieved ≥ 85% of maximum age-predicted heart rate. a workload of ≥ 10 mets was achieved in 25.4%; 50.3% attained 7-9 mets, and 24.4% reached < 7 mets. there was a stepwise decrease in prevalence of any ischemia and significant ischemia (≥ 10% of the left ventricle (lv)) as workload increased (p = 0.037). patients achieving ≥ 10 mets had a 3.1% prevalence of ≥ 10% lv ischemia (1.2% in those without st depression). cardiac death and mace rates in the ≥ 10 mets subgroup were 0.6%/year and 2.6%/year over a median 7.0 years of follow-up. a substantial proportion of older adults who undergo exercise spect mpi can achieve ≥ 10 mets. this subgroup has low rates of significant lv ischemia and mace. the favorable diagnostic and prognostic implications of achieving a high workload in an older adult population suggest it is feasible, with certain exceptions, to include this subgroup in workload-based strategies of provisional imaging.